Anne Hillairet De Boisferon

Claudia Kubicek

Judit Gervain

Gudrun Schwarzer

Hélène Loevenbruck

Anne Vilain

Mathilde Fort

David Méary

Olivier Pascalis
email: olivier.pascalis@univ-grenoble-alpes.fr

Language familiarity influences own-race face recognition in 9-and 12-month-old infants

Keywords: infant, face, recognition, native language, non-native language

 investigated whether 6-month-old infants associate faces (own-race, other-race) with language (native, non-native). Caucasian monolingual English-learning infants were presented with pictures of faces that were either from their own race (Caucasian), or another race (Chinese). For the infants in the

Introduction

The development of face processing and speech perception show intriguing commonalities, suggesting that the two cognitive systems interact during development [START_REF] Maurer | Perceptual Narrowing During Infancy: A Comparison of Language and Faces[END_REF][START_REF] Pascalis | On the Linkage between Face Processing, Language Processing, and Narrowing during Development[END_REF]. One of the most interesting similarities is that the maturation of both systems undergoes a phenomenon often referred to as perceptual narrowing or perceptual attunement. This phenomenon describes the fact that infants are born with the ability to discriminate a wide range of stimuli (regardless of their frequency in their perceptual environment) based on low-level properties of the sensory input. However, at the end of their first year, they have become experts in recognizing the stimuli that are the most frequent in their perceptual environment, while they have lost the ability to recognize contrasts that are uncommon or absent in their daily life. For language learning, seminal work by [START_REF] Werker | Cross-language speech perception: Evidence for perceptual reorganization during the first year of life[END_REF] showed that 3-to 9-month-old infants are able to discriminate native as well as non-native phonetic contrasts. At 12 months however, infants are, as adults, only able to discriminate phonetic contrasts that belong to their native language (see also, [START_REF] Weikum | Visual language discrimination in infancy[END_REF][START_REF] Pons | Narrowing of intersensory speech perception in infancy[END_REF]. For face recognition, [START_REF] Kelly | The Other-Race Effect Develops During Infancy. Evidence of Perceptual Narrowing[END_REF] evidenced a similar phenomenon: while both 3-and 6-month-olds are able to recognize own-as well as other-race faces, 9-month-olds are, as adults, only able to recognize faces of their own race, the Other Race Effect (ORE, [START_REF] Rossion | An experienced-based holistic account of the other-race face effect. The Oxford Handbook of Face Perception[END_REF], for a review). These two phenomena have been studied separately, and the nature of the interaction between language and face systems remains understudied. However, this interaction could have important implications for current models of both face, and language perception.The goal of the present study is to directly explore the influence of language learning (and more specifically, language familiarity) on the development of face recognition in infancy.

Language has also been found to influence face processing in adults. [START_REF] Baus | Speak My Language and I Will Remember Your Face Better: An ERP Study[END_REF] investigated how language familiarity (native vs. non-native) affects own-race face recognition in adults. Their participants learned faces accompanied by voices speaking either in their native or non-native language, and had to recognize them in a subsequent test. Results showed that they remembered more accurately the faces previously paired with their native language than the other faces, showing that language familiarity somewhat improves the recognition of individuals [START_REF] Baus | Speak My Language and I Will Remember Your Face Better: An ERP Study[END_REF]. In the same line of arguments, [START_REF] Kandel | The impact of linguistic experience on face recognition: Testing the Other-Race-Effect in Bilinguals and Monolinguals[END_REF] have shown that early language experience impacts on face processing abilities in adulthood. They found that bilingual adults did not exhibit the classic Other-Race Effect, as opposed to monolingual with the same level of experience with other race faces. Hence, early exposure to more than one language shapes perceptual organization beyond language processing, notably extending to face processing (see also [START_REF] Zhang | Heritage-culture images disupt mm g ' c d-language processing through triggering first-language interference[END_REF]).

Taken together, these pieces of converging evidence suggest that language familiarity influences face processing in adults. Is there a similar influence of language on face processing during infancy? Do language and face processing systems develop independently from each other or do they interact early on, at stages when the representation for faces and speech are not mature yet? This question is important as it could radically improve our understanding of how infants adapt so quickly to their social environment, but also of the mechanism at play for face and language processing. Some recent studies suggest that language and face processing systems interact during the first year [START_REF] Krasotkina | Perceptual Narrowing in Speech and Face Recognition: Evidence for Intra-individual Cross-Domain Relations[END_REF][START_REF] Xiao | Narrowing in face and speech perception in infancy: Evidence for developmental change in the relations between domains[END_REF], see also Pascalis et al., 2014, for a review). Using a within-participant design, [START_REF] Xiao | Narrowing in face and speech perception in infancy: Evidence for developmental change in the relations between domains[END_REF] measured 3-, 6-, 9-, and 12-month-old f ' perceptual discrimination for language (native vs. non-native phonetic contrasts) and individual face recognition (own vs. other-race faces). While no correlation was found for face recognition and language discrimination scores at 3 and 6 months of age, their results showed significant relationships between these two scores at 9 and 12 months of age. At 9 months, they found a negative correlation between the extent of perceptual narrowing in the face domain and that in the language domain, suggesting that at this age, systems might somewhat compete with each other as they vie for attentional capacity as a limited resource. Conversely, at 12 months, a positive correlation was found, suggesting that these two systems no longer compete with each other but rather improve c ' fu c g. The goal of the present study is to explore the role of language familiarity on infant face recognition.

matching condition, the Caucasian faces were systematically presented with a voice speaking in the f ' v gu g (English) while the Chinese faces were always accompanied by a non-native language soundtrack (Mandarin). Infants in the mismatching condition perceived the opposite pairings. Results showed that 6-month-olds in the matching condition looked longer at the face-voice pairings than infants in the non-matching condition. This early "matching preference" suggests that 6month-olds have already developed a multisensory expectation of how face race and language are associated in their environment.

However, there is no study directly investigating the impact of language familiarity on how infants learn and recognize own-race faces. Indeed, beyond initial preferences, it is crucial to understand whether language influences how infants perceptually encode the faces of the people that surround them. In the present study, we tackled this question by testing how language familiarity impacts 9-and 12-month-old infants' ability to recognize faces from their own race. We chose to test these abilities at a period when both age groups have become experts in categorizing their own-race faces [START_REF] Kelly | The Other-Race Effect Develops During Infancy. Evidence of Perceptual Narrowing[END_REF] but language learning is still under way. Indeed, although infants can recognize their native language from birth [START_REF] Moon | Two-day-olds prefer their native language[END_REF], their first year is devoted to tuning to the specific phonological system of that language, with perceptual attunement to native vowels at around 6 months [START_REF] Kuhl | A new view of language acquisition[END_REF], and to native consonants at around 10-12 months of age [START_REF] Werker | Cross-language speech perception: Evidence for perceptual reorganization during the first year of life[END_REF].

Regarding lexical development, infants start learning word-object associations at around 6 months [START_REF] Bergelson | At 6 -9 Months, Human Infants Know the Meanings of Many Common Nouns[END_REF], but they will only start using such associations as communicative tools at around 12 months [START_REF] Bates | Individual differences and their implications for theories of language development[END_REF]. Therefore, 9 and 12 months are two age periods when infants will process native vs. non-native language very differently. Moreover, infants between 9 and 12 months of age also undergo brain and attentional maturation (see De Diego-Balaguer, Martinez-Alvarez & Pons, 2016, for a review). As we will discuss later on, all of these factors could presumably be of importance as they influence how infants selectively attend to [START_REF] Lewkowicz | Infants deploy selective attention to the mouth of a talking face when learning speech[END_REF] and potentially recognize the faces of others.

To test the effect of language familiarity, we selected two phonetically and rhythmically distant languages, that are supposed to be easily discriminable from one another: French and German.

Notably, German and French belong to different rhythmic classes that neonates can already discriminate solely on the basis of the low-pass filtered acoustic speech signal [START_REF] Mehler | A precursor of language acquisition in young infants[END_REF][START_REF] Nazzi | Language discrimination by newborns: Toward an understanding of the role of rhythm[END_REF][START_REF] Ramus | Correlates of linguistic rhythm in the speech signal[END_REF].

In Experiment 1, we tested the influence of language familiarity on face recognition by familiarizing 9-and 12-month-old French-learning infants with audiovisual clips of a Caucasian native bilingual French-German speaker, talking to half of them in their native language (French) and to the other half in a non-native language (German). In p p c u f p ' f c was presented side by side with a picture of a novel face. We used greater looking time to the novel face relative to the familiarized face at test to index face recognition. That is, if infants had recognized the face of the speaker from the familiarization phase, they were expected to show a novelty effect, namely a visual preference for the novel over the familiar face (the p ' f c they had been familiarized with). If language familiarity influences face recognition, we expected to observe, in line with previous findings, better face recognition performance for the infants familiarized to the speaker talking in their native language. We also expected this effect of language familiarity on face recognition to be stronger in the 12-month-olds than in the 9-month-olds, due to more mature language and/or selective attention skills.

Experiment 1

Method

Participants

The present study was conducted according to guidelines laid down in the Declaration of Helsinki, with written informed consent obtained from a parent or guardian for each child before any assessment or data collection. All procedures involving human subjects in this study were approved by the CERGA IRB00010290-2018-02-06-39 at the University Grenoble Alpes.

Seventy-two infants participated in Experiment 1. Thirty-six were 9-month-olds (M age = 287 days, SD age = 4.4 days, 16 females, 20 males), and the 36 others were 12-month-olds (M age = 376 days, SD age = 4.2 days, 15 females, 21 males). For each age group, half of the infants (N=18) were assigned to the Native Language condition, while the other half was assigned to the Non-native condition. Infants were healthy, full-term participants, recruited from the maternity ward of the Centre Hospitalier Universitaire Grenoble Alpes in France. They were all Caucasians and growing in a monolingual French-speaking environment (according to parental report infants were exposed to

French more than 95% of the time). Eight additional infants (two 12-month-olds) were tested, but excluded from the analyses because they did not complete the procedure due to crying or fussiness.

According to parental reports, the infants had had no direct exposure to German prior to their participation.

Stimuli

Apparatus and Procedure

Infants were seated on their parent' p in a dimly illuminated room, ~ 60 cm away from a 22-inch computer screen. Parents were asked not to intervene, interact, nor speak with their infant during the experiment. Stimuli were presented using the E-prime 2.0 software (Psychology Software Tools, Pittsburgh, PA, USA). Two loudspeakers (Dell A225) placed behind the screen, on the left and right side, transmitted the audio soundtracks. A low-light video camera, located above the monitor, was used to record infant ' looking behavior. The video recordings were subsequently digitized and analyzed with a frame-by-frame offline coding procedure. All parents signed a written consent form for their infant prior to the experiment.

The experimental procedure was divided into two phases: familiarization and test.

Familiarization trial

Infants were presented with a video clip of the face of one of the two female speakers, talking in German or in French, displayed at the center of the screen. Both the language spoken by the speaker (French/German) and the speaker identity were counterbalanced across participants. Before each trial an attention getter was presented until the infant looked at the middle of the screen. Each trial ended after the video (total duration: 30 seconds). In other words, the familiarization duration was not infant controlled.

Test trials

We used a preferential looking technique to test face recognition. Immediately after the familiarization, the face of the speaker presented in the familiarization phase and a novel face (the speaker the infant was not familiarized to) were displayed side-by-side on the monitor, separated by a 12 cm gap. They were presented for two test trials, lasting five seconds each. The trial started when the infant looked at one of the two stimuli and ended after 5 seconds had elapsed. The side (left/right) where the novel face appeared was counterbalanced across participants and trials. An attention getter screen was presented before each trial until the infant looked at the middle of the screen.

Eye movements were recorded throughout and the recording digitized to be analyzed frame-by-frame by two independent observers on a computer using homemade software. The observers were blind as to which stimulus was presented on each side. Inter-observer agreement was computed on 33% of the participants from the final sample collapsed across age. It showed a high reliability score (Pearson r = .96). Importantly, none of the participants were excluded because of side bias during testing (> 95% looking time to one side).

Results

Familiarization

The time infants spent looking at the speaker during the familiarization phase did not vary according to age group, language familiarity (M = 27.75s, SD = 2.7 for German and M =27.13s, SD = 3.4 for were significantly above 50%, this would indicate a novelty preference. We then performed an arcsine transformation of these scores for each participant in each condition, to avoid potential ceiling or floor effects [START_REF] Winer | Statistical principles in experimental design[END_REF]. To handle missing data and to be able to consider that the effect of fixed factors could vary among participants, we used a mixed-effects models and analyzed the data with R (R Core Team, 2012) using the lme4 package (Bates, Maechler, Bolker, & Walker, 2015). Participants and Trial number (first, second) were random factors, while Age (9 vs. 12 months) and Language Familiarity (Native vs. Non-Native) were between-participants fixed factors and Face Familiarity (Familiar Face vs. Novel Face) a within-participant fixed factor. The Familiar Face condition was treated as baseline and parameters were estimated for the Novel Face condition. Results averaged across trials are presented in Figure 1, first and second columns. Statistical analyses did not yield any significant effect nor interaction between factors (all t < 1) 1 . The effect of Face Familiarity was only significant for the 12-month-olds in the Native language condition (Estimate = .10, SE = .03, t = 3.3, p < .005), but failed to reach significance for the three other group of infants (12-month-olds, Non-Native language: t < 1; 9-month-olds, Native language: β = .07, SE = .04, t = 1.6, p = .12, Non-Native language: β = .07, SE = .04, t = 1.4, p = .17). We further discuss those results in the next section.

1 Fixed-effects estimates and standard errors along with t and p values were estimated using S w ' pp x m f d g f f d m.

Discussion

Our results suggest that 9-month-olds did not recognize the familiar face over the novel face, regardless of whether she spoke in their native languages or not. At 12 months, results are more difficult to interpret. Further analyses suggest that 12-month-old c g p ' face, but only in the native language condition. However, no significant interaction was observed in the omnibus analysis, suggesting that this last effect was weak and has to be interpreted cautiously. Taken together, these results suggest that robust recognition for both age group is not found after a familiarization using videos of a face speaking non-native language.

When comparing these data with previous literature, our results are intriguing. Infants did not seem to robustly recognize a face they had been familiarized with for 30 seconds. By contrast, previous studies by [START_REF] Pascalis | Is Face Processing Species-Specific During the First Year of Life?[END_REF] evidence robust own-race face recognition from 9 months of age, using familiarization phases even shorter than ours (20s-vs 30s-long, respectively). Thus, it is unlikely that in the present study, the lack of clear evidence for face recognition could be due to immature face processing skills.

We consider several explanations to account for our results. First, the lack of clear evidence for ownrace face recognition in Experiment 1 could be due to a peculiarity of our stimuli. It could be that for some reasons, the faces we used were somewhat hard for infants to distinguish from each other.

However, we used successfully those dynamic stimuli in another study (Kubicek et al., 2014) making this argument unlikely. Another possible explanation could come from the use of a complex dynamic/talking face, rather than the mere still picture of a face, in the familiarization phase. In previous studies on face recognition, such as [START_REF] Pascalis | Is Face Processing Species-Specific During the First Year of Life?[END_REF], infants were only familiarized with static pictures of faces. Using talking faces could have induced a supplementary cognitive load in 9and 12-month-olds: they could have been distracted by the complexity of the dynamics of the talking face, preventing them to process the identity of the speaker. Similarly, they could have been overwhelmed by the language input. In line with this argument, two previous eye-tracking studies, using audiovisual talking faces, showed that at 8, 10 and 12 months of age, infants looked a large amount of time at the mouth region of a female speaker [START_REF] Lewkowicz | Infants deploy selective attention to the mouth of a talking face when learning speech[END_REF]Pons, Bosch & Lewkowicz, 2015;Kubicek et al., 2014). Thus, 9-and 12-month-d ' failure to recognize an own-race face could be due to the fact that the face spoke during the familiarization, inducing greater looking time at the mouth region of the talking face than we should have observed if we had presented own-race static faces. This attentional shift to the mouth, could have lessened their ability to process the face identity, with insufficient attention to other internal features such as the eye region of the speaker. This selective attention to the mouth would impinge on face identity processing during familiarization.

To test these hypotheses, we conducted a second study. Instead of using talking faces in the familiarization phase, we only kept the auditory soundtrack of the nursery rhyme, accompanied by the static picture of the speaker's face, getting closer to the classical paradigms used in infant face recognition literature. If the results of Experiment 1 were only due to a peculiarity of our face stimuli or to a lack of language maturation, we should observe the same results in Experiment 2. If the results of Experiment 1 were due to the presence of an audiovisual dynamic face attracting attention to the mouth region and preventing infants from memorizing facial identity, by using still pictures, we should circumvent this mouth attraction and observe a novelty effect in both age groups. If, as hypothesized in Experiment 1, language familiarity influences face recognition processes, we should observe a stronger novelty effect for infants familiarized with the Native rather than to the Non-Native language.

Experiment 2

Method Participants

Seventy-two infants participated in Experiment 2. Thirty-six were 9-month-olds (M age = 284.75 days, SD age = 6.28 days, 23 females while the other 36 infants were 12-month-olds (M age = 382.3 days, SD age = 19.6 days, 20 females). For each age group, half of the infants (N=18) were assigned to the Native Language condition, while the other half was assigned to the Non-native condition. Infants were healthy, full-term participants, recruited from the maternity ward of the Centre Hospitalier Universitaire Grenoble Alpes in France. They were all Caucasians and growing in a monolingual French-speaking environment (according to parental report infants were exposed to French more than 95% of the time). Ten additional infants (4 12-month-olds) were tested, but excluded from the analyses because they did not complete the procedure due to crying or fussiness. According to parental reports, these infants had no direct exposure to German prior to their participation.

Familiarization

The familiarization phase was identical to Experiment 1 except that instead of seeing the talking face of the speaker, infants were presented with a still picture of the p ' face displayed at the center of the screen. It was accompanied by a 30s soundtrack of the nursery rhyme extracted from the video clips of Experiment 1.

Test trials

The test trials were exactly the same as in Experiment 1. As in Experiment 1, no participant was excluded because of side bias during testing (> 95% looking time to one side).

Results and Discussion

Familiarization Trials

The time infants spent looking at the speaker during the familiarization phase did not vary according to age group, language familiarity (M = 23.3s, SD = 4.2 for German and M =24.01s, SD = 4.1 for French) nor speaker identity (all p > .05).

Preference Test Trials.

Results from Experiment 2 averaged across trials are presented in Figure 1, second column. We conducted a mixed model analysis using Language Familiarity and Face Type as fixed factors on the arsine transformation of the preference scores from Experiment 2. Initially, Age (9 vs 12 months) was also declared as a fixed factor, but it did not significantly increase the variance accounted for and was thus excluded from the final model. In contrast with Experiment 1, results revealed a significant main effect of Face Familiarity (Estimate = .18, SE = .03, t = 6.03, p < .001) and Language Familiarity (Estimate = .08, SE = .03, t = 2.6, p < .05), as well as a significant interaction between both factors (Estimate = -.15, SE = .04, t = -3.6, p < .005). Nine-month-old (Estimate = .14, SE = .03, t = 4.1, p <

.001) and 12-month-old (Estimate = .22, SE = .04, t = 5.6, p < .001) infants in the Native Language condition looked significantly longer at the novel face in the test phase, suggesting that they recognized the face they were familiarized with. However, neither 9-nor 12-month-olds (both t < 1) in the Non-Native condition looked significantly longer at the novel face in the test phase.

We then compared results from Experiment 1 and 2, conducting a mixed model analysis using Language Familiarity and Face Type as fixed factors on the arsine transformation of the preference scores from both experiments, adding Experiment (Experiment 1, Experiment 2) as a betweenparticipant factor. Initially, Age (9 vs 12 months) was also declared as a fixed factor, but it did not significantly increase the variance accounted for and was thus excluded from the final model. While no main effect of Experiment was found (Estimate =.04, SE = .03, t = 1.2, p = .22), the interaction between Face Familiarity and Experiment was significant (Estimate = -.10, SE = .04, t = -2,4, p < .05)

and the other between Face Familiarity, Experiment and Language Familiarity almost reached significance (Estimate =.12, SE = .06, t = 2,1, p < .05). Taken together, these analyses show that results in Experiment 2 statistically differ from those in Experiment 1.

Discussion

The second experiment was designed to determine if the results of Experiment 1 were a consequence of 1) a peculiarity of the face stimuli we used, 2) the influence of language maturation on face processing, or 3) the audiovisual dynamic stimuli used (videos instead of still pictures) in the familiarization phase. The results are more in line with the last hypothesis. In contrast with Experiment 1, 9-and 12-month-old infants in Experiment 2 seem to have learned the familiar face that had been presented with the native language. However, infants from the same age groups who had been familiarized with the face associated with the non-native language did not display evidence of recognition afterwards.

General discussion

The goal of the present study was to explore the effect of language familiarity on how infants recognize own-race faces. The first important finding is that when 9-and 12-month-old infants were familiarized with a video of a dynamic talking face, they did not seem to clearly recognize it later on (Experiment 1), regardless of language familiarity. As mentioned in the discussion of Experiment 1, these findings contrast with previous literature on own-race face recognition in infancy. One Another compatible interpretation of the data is that visual still faces are easier to process than dynamic videos, facilitating the task in the younger infants. The ability of 9-month-old infants to recognize a face when it speaks their native language could be explained by a lesser cognitive load when processing a native sound, resulting in a better processing of the visual stimulus. When presented with a still image, the processing would be even easier than when presented with a dynamic succession of images (a video). To explore this hypothesis, we compared the amount of time infants spent looking at the face of the speaker during the familiarization phase between Experiment 1 and Experiment 2. We used a mixed-effects model on the proportion of total Looking time for the familiarization phase preference scores during the test phase, using Language Familiarity, Age and

Experiment as fixed factors. The effect of Experiment was significant (Estimate = .12, SE = .03, t = 4,2, p < .001), indicating that infants who were familiarized to the Video of the talking face in Experiment 1 spent more time looking at the face than infants who were familiarized to the Static face in Experiment 2. No other effect nor interaction was significant (all p > .48). This increased familiarization time could potentially reflect a greater cognitive load in Experiment 1, because infants needed more time to process the dynamic face rather than the static face of Experiment 2. While one has to remain cautious about this post-hoc interpretation, as a great cognitive load could also lead to decrease looking times, we believe that further research is needed to explore whether longer familiarization phases could promote how infants recognize more ecological dynamic faces.

Second, our results suggest that at 9 and 12 months of age, hearing a non-familiar language, as opposed to a familiar one, somewhat reduces f ' ability to learn a still face of their own-race that is associated with that language (Experiment 2). This result, brings a new perspective to the literature on infant cognition. Indeed, previous studies have shown that 9-month-old infants are able to recognize own-race faces even after a short presentation time [START_REF] Pascalis | Is Face Processing Species-Specific During the First Year of Life?[END_REF]. The present study suggests that this recognition ability can be modulated by language familiarity: at 9 and 12 months of age, hearing a non-native language somewhat reduces the efficiency of infants' w -race face recognition. Importantly, it cannot be explained by a simple a lack of exposure, as the looking time spent on the face during the familiarization phase did not differ between non-native and native language conditions (see the analysis on the looking times of the familiarization phase presented in the previous paragraph).

These results are broadly in line with adult data, which show that face processing is modulated by the context in which the face is learned [START_REF] Baus | Speak My Language and I Will Remember Your Face Better: An ERP Study[END_REF]. In this study adult participants were presented with faces while hearing a native language (i.e., Spanish) or a non-native second language (i.e., English). In a subsequent test, participants were better at recognizing the faces that had been paired with the native language. Nonetheless, adults in the non-native language condition still performed above chance. This indicates that listening to a language they were somewhat familiar with but did not fully master only partially impaired face recognition. These last results contrast with the present infant data. Indeed, the present results suggest that face recognition is prevented in the non-native language condition. This could be due to the fact that, as opposed to [START_REF] Baus | Speak My Language and I Will Remember Your Face Better: An ERP Study[END_REF], we used a language that French-learning infants had never been exposed to (German). Further research needs to be done to study whether, in infancy, the degree of familiarity with a given language gradually influences how faces are encoded or whether it is an all-or-none type of phenomenon.

Regarding the cognitive mechanisms that could account for the present results, one possible interpretation is that hearing a completely unknown language tampers withat least partially-ownrace faces recognition processes . From a social point of view, it could be that infants categorize faces presented with a unknown language as out-group, which would trigger, as opposed to faces presented with a native language, a broader encoding of the face in memory, limiting its later recognition.

Alternatively, social categorization as in-group would enhance f ' attention and memory processes to encode fine-grained representations of the faces that speak their native language (see [START_REF] Kinzler | The native language of social cognition[END_REF]2009;[START_REF] Pietraszewski | Evidence that accent is a dedicated dimension of social categorization, not a byproduct of coalitional categorization[END_REF], for more discussion on the topic). A second and perhaps non-mutually exclusive hypothesis could be that another type of learning happens in that condition, derailing -at least temporarily-f ' b y to encode own-race faces. Hearing a novel foreign language could orient f ' attention away from face identity processes and lead them to solely focus on the novel auditory stream, at least partially tampering with visual face encoding and its subsequent recognition (see [START_REF] Wickens | Multiple resources and mental workload[END_REF]Pickel and Staller, 2012 for such a hypothesis in adults). This interpretation fits well with few theoretical frameworks suggesting that the development of language and attention skills constrains visual perceptual narrowing for faces (see [START_REF] Markant | Attention and Perceptual Learning Interact in the Development of the Other-Race Effect[END_REF], for a review).

It is however, important to note that the data provided by the present study could not be face specific.

It is indeed possible that infants in Experiment 2 that the apparent association between faces and language might be a general outcome of conditions in which infants need to process a great deal of novel information (in the Non-Native language condition) versus less novelty (in the Native language condition). Further research is needed to investigate whether infants would see their recognition of non-social random objects influenced by the presence of native familiar versus non-native unfamiliar language, to see if the association is specific to the social interaction of faces and language.

From a more general perspective, this study also shows that auditory linguistic information as well as visual cues are at play when identifying conspecifics, as early as 9 months of age. At a neural level, this means that at least from this age mechanisms responsible for online face and language processing interact with each other. Further research should address the role of specific language and/or face experience where infants grow in an environment where bilingualism and/or multi-ethnic faces are the norm.

Familiarization

  stimuli were four video clips of two bilingual female speakers, native of both speakers were recorded against a blue background, looking directly at the camera with a neutral expression. All videos were matched in image size and time duration. Each 30-second video showed a full-face image of the speaker and measured 20.6 cm x 18 cm when displayed on the monitor. Sound was presented at conversational sound pressure level. In the test phase, closed. All individual pictures were mounted on a uniform dark blue background. All stimuli were resized identically to ensure uniformity. One speaker was used for familiarization and the second one as a novel face during the test. The face presented during the familiarization was counterbalanced between the participants.

  French) nor speaker identity (all p > .05). All data for the familiarization and Test phase of Experiment 1 and 2 can be downloaded here: https://osf.io/g7wsv/?view_only=10675c79c945474da8cd9dc1551fe96c infants spent looking at the novel stimulus by the total time they spent looking at both the novel and the familiar face during the test phase (cf. Figure1, first column). If these scores

  explanation for this pattern of results lies in the way infants distribute their visual attention when viewing dynamic talking faces. As mentioned in the discussion of Experiment 1, Lewkowicz & Hansen-T f (2012)'s findings indicate that 8-to 12-month-olds spend a great amount of time focusing on the mouth region (rather than on the eyes region) of a talking face. It is thus possible that in Experiment 1, 9-and 12-month-olds spend a great amount of time focusing on the mouth region of the speaker. This mouth attraction may have prevented them from robustly encoding and remembering the whole face identity, since they would have allocated insufficient attention to other crucial facial features for face recognition (i.e., the eyes region). Following this rationale, one might de Boisferon, Tift, Minar &Lewkowicz (2015) found that in line with our present interpretation, 10-month-old infants looked less at the mouth region of a native speaker in an asynchronous condition-rather than in a synchronous condition. Additionally, another eye-tracking research byXiao, Quinn, Liu, Ge, Pascalis & Lee (2015) showed that 9-month-old infants would spend more time looking at the eyes rather than at the mouth region of a static own-race face.Conversely, they shifted their pattern of attention favoring the mouth over the eyes region when looking at videos of dynamic silent faces. It is important to note that this interpretation gaze during the study. Further research should thus explore whether and how different attentional strategies to static and dynamic (talking vs. non-talking) faces impact face recognition.

this work was supported by ANR-DFG BabyFaceSpeech (ANR-17-FRAL-0014-01). The authors declare no conflicts of interest with regard to the funding source for this study.

Regarding this question, pioneering work by Kinzler, Dupoux and Spelke (2007) investigated the f u c f gu g f m y f


Corentin Iltis
email: corentin.iltis@u-bourgogne.fr.

Philippe Louâpre

Karolina Pecharová

Denis Thiéry

Sébastien Zito

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Jérôme Moreau

Are life-history traits equally affected by global warming? A case study combining a multi-trait approach with fine-grain climate modeling

Keywords: Climate models, defensive behaviors, energetic reserves, global warming, immunity, multitrait approach

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Temperature is undeniably one of the most important factors determining individual performance, species evolution and distribution [START_REF] Angilletta | Thermal adaptation: a theoretical and empirical synthesis[END_REF][START_REF] Cameron | Regression-based tests for overdispersion in the Poisson model[END_REF]. In ectothermic animals like insects, whose body temperature and performance are closely related with environmental temperature, the link between a surrogate for individual performance (e.g. development and growth rates, reproductive output) and environmental temperature is typically modeled by an asymmetric and unimodal curve called a thermal performance curve [START_REF] Martin | Why 'suboptimal' is optimal: Jensen's inequality and ectotherm thermal preferences[END_REF][START_REF] Sinclair | Can we predict ectotherm responses to climate change using thermal performance curves and body temperatures?[END_REF]. As temperature increases, individual performance gently rises to a single maximum value associated with a thermal optimum, and thereafter performance declines rapidly.

Thermal performance curves may help to predict how organisms will cope with changes occurring in their thermal environment, such as those related with anthropogenic climate disturbance [START_REF] Deutsch | Impacts of climate warming on terrestrial ectotherms across latitude[END_REF][START_REF] Estay | The role of temperature variability on insect performance and population dynamics in a warming world[END_REF][START_REF] Sinclair | Can we predict ectotherm responses to climate change using thermal performance curves and body temperatures?[END_REF]. Indeed, one commonly used way to assess the biological consequences of global warming consists of experimentally tracking the variation in organism's performance following exposure to warming conditions designed to simulate future temperatures (for examples, see [START_REF] Bauerfeind | Simulating climate change: temperature extremes but not means diminish performance in a widespread butterfly[END_REF][START_REF] Fischer | Strong negative effects of simulated heat waves in a tropical butterfly[END_REF][START_REF] Klockmann | Fitness implications of simulated climate change in three species of copper butterflies (Lepidoptera: Lycaenidae)[END_REF]. In this regard, it is now widely accepted that comparing fluctuating thermal regimes (instead of constant temperatures) significantly improves the ecological realism of global warming experiments, considering the daily variations of temperatures experienced by organisms in their natural settings [START_REF] Bozinovic | Thermal tolerance and survival responses to scenarios of experimental climatic change: changing thermal variability reduces the heat and cold tolerance in a fly[END_REF][START_REF] Bozinovic | The mean and variance of environmental temperature interact to determine physiological tolerance and fitness[END_REF][START_REF] Colinet | Insects in fluctuating thermal environments[END_REF][START_REF] Paaijmans | Temperature variation makes ectotherms more sensitive to climate change[END_REF][START_REF] Zeh | Constant diurnal temperature regime alters the impact of simulated climate warming on a tropical pseudoscorpion[END_REF]. The existing literature suggests complex patterns of biological responses to warmer conditions because of the combined effects of mean temperature and thermal fluctuations on individual performance [START_REF] Colinet | Insects in fluctuating thermal environments[END_REF][START_REF] Estay | The role of temperature variability on insect performance and population dynamics in a warming world[END_REF][START_REF] Kingsolver | Fluctuating temperatures and ectotherm growth: distinguishing non-linear and time-dependent effects[END_REF]. Part of this variability in thermal responses might be explained by Jensen's inequality, which applies to non-linear functions such as those inherent to thermal performance curves [START_REF] Martin | Why 'suboptimal' is optimal: Jensen's inequality and ectotherm thermal preferences[END_REF]). Jensen's inequality posits that thermal fluctuations around a mean temperature below the thermal optimum (i.e. in the concave part of the thermal performance curve) will enhance performance, while the reverse trend should be observed once the mean temperature of the thermal regime exceeds the thermal optimum, in the convex part of the thermal performance curve [START_REF] Bozinovic | The mean and variance of environmental temperature interact to determine physiological tolerance and fitness[END_REF][START_REF] Foray | The impact of thermal fluctuations on reaction norms in specialist and generalist parasitic wasps[END_REF][START_REF] Kingsolver | Fluctuating temperatures and ectotherm growth: distinguishing non-linear and time-dependent effects[END_REF][START_REF] Paaijmans | Temperature variation makes ectotherms more sensitive to climate change[END_REF][START_REF] Terblanche | Thermal variability alters climatic stress resistance and plastic responses in a globally invasive pest, the Mediterranean fruit fly (Ceratitis capitata)[END_REF]. In a context of fluctuating thermal environments, an increase in mean temperature attributable to global warming could be expected to depress organism performance through transient or permanent exposure to stressful thermal conditions during the warmest hours of the cycle [START_REF] Colinet | Insects in fluctuating thermal environments[END_REF][START_REF] Paaijmans | Temperature variation makes ectotherms more sensitive to climate change[END_REF][START_REF] Vasseur | Increased temperature variation poses a greater risk to species than climate warming[END_REF]. This is especially true if the increase in mean temperature is accompanied with a widening of thermal fluctuations [START_REF] Paaijmans | Temperature variation makes ectotherms more sensitive to climate change[END_REF][START_REF] Terblanche | Thermal variability alters climatic stress resistance and plastic responses in a globally invasive pest, the Mediterranean fruit fly (Ceratitis capitata)[END_REF][START_REF] Vasseur | Increased temperature variation poses a greater risk to species than climate warming[END_REF]. Indeed, high levels of temperature variance have been shown to decrease an organism's ability to tolerate a thermal stress by limiting the expression of plastic responses and reducing the possibility for appropriate acclimation process to take place [START_REF] Terblanche | Thermal variability alters climatic stress resistance and plastic responses in a globally invasive pest, the Mediterranean fruit fly (Ceratitis capitata)[END_REF].

Responses to warming conditions might, however, greatly vary depending on the biological traits measured to infer individual performance, thereby highlighting the need for a multi-trait approach -involving measurements on a large number of traits -in global warming experiments [START_REF] Fischer | Assay conditions in laboratory experiments: is the use of constant rather than fluctuating temperatures justified when investigating temperature-induced plasticity?[END_REF][START_REF] Karl | Temperature extremes and butterfly fitness: conflicting evidence from life history and immune function[END_REF][START_REF] Laughton | Responses to a warming world: Integrating life history, immune investment, and pathogen resistance in a model insect species[END_REF]. Indeed, fitness-related traits in a given species might differ regarding their thermal optima and associated thermal performance curves [START_REF] Laughton | Responses to a warming world: Integrating life history, immune investment, and pathogen resistance in a model insect species[END_REF][START_REF] Seehausen | Developmental and reproductive responses of the spruce budworm (Lepidoptera: Tortricidae) parasitoid Tranosema rostrale (Hymenoptera: Ichneumonidae) to temperature[END_REF].

Experimental warming might thus yield different effects on the expression of these traits depending on whether thermal conditions applied encompass supraoptimal temperatures for the expression of the traits considered. For instance, in the Indian meal moth Plodia interpunctella (Lepidoptera: Pyralidae), a rise in mean constant temperature from 20°C to 30°C led to an almost twofold decrease in developmental time from egg to adult, while reducing adult lifespan after mating by 32% and increasing the count of immune cells (hemocytes) in larvae hemolymph by more than 50% [START_REF] Laughton | Responses to a warming world: Integrating life history, immune investment, and pathogen resistance in a model insect species[END_REF]. Furthermore, biological traits are linked to each other by energetic trade-offs and thermal conditions are known to influence resource allocation towards different functions. Convincing examples entail trade-offs between immunity and reproduction [START_REF] Adamo | Some like it hot: the effects of climate change on reproduction, immune function and disease resistance in the cricket Gryllus texensis[END_REF] as well as between immunity and heat tolerance [START_REF] Fischer | Assay conditions in laboratory experiments: is the use of constant rather than fluctuating temperatures justified when investigating temperature-induced plasticity?[END_REF][START_REF] Karl | Temperature extremes and butterfly fitness: conflicting evidence from life history and immune function[END_REF]. Experimental studies employing a multi-trait approach usually incorporate both traits linked with population dynamics (e.g. development and growth rates, survival rates, egg production) and interspecific relationships (e.g. defensive traits such as defensive behaviors and immunity) [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF][START_REF] Karl | Temperature extremes and butterfly fitness: conflicting evidence from life history and immune function[END_REF][START_REF] Laughton | Responses to a warming world: Integrating life history, immune investment, and pathogen resistance in a model insect species[END_REF]. Indeed, the former help to predict the future population dynamics of the focal species, but species will not respond in isolation to climate disturbance as they are tightly connected by ecological linkages, more specifically trophic interactions [START_REF] Jeffs | Effects of climate warming on host-parasitoid interactions[END_REF][START_REF] Van Der Putten | Predicting species distribution and abundance responses to climate change: why it is essential to include biotic interactions across trophic levels[END_REF]. Integrating defensive traits involved in interspecific relationships -such as host-parasitoid associations -is thus crucial to provide significant insight into how a given species might respond to global warming with respect to its associated ecological context [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF]. In spite of a fairly robust literature about the effects of thermal fluctuations on performance in a climate change perspective, still few studies have to date associated the ecological realism provided by the use of realistic fluctuating regimes with the multi-trait approach, measuring different traits related with both population dynamics and species interaction (for examples, see Fischer et al., 2014;[START_REF] Klockmann | Fitness implications of simulated climate change in three species of copper butterflies (Lepidoptera: Lycaenidae)[END_REF]. Consequently, little is known about the effects of realistic daily thermal cycles on the expression of a broad series of traits within the framework of global warming. Filling this knowledge gap could improve our mechanistic understanding of the responses of traits, individuals and populations to facets of climate change.

In this context, we here explored the consequences of global warming simulated at a local scale for several aspects of an insect's performance. To realistically simulate global warming under controlled conditions, we built two daily fluctuating regimes: one current regime according to local climate observations and one future regime according to the finegrain predictions provided by climate models in our focal area (Eastern France). We focused on caterpillars of the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae), one of the most severe pests for wine-making activity in Palearctic region [START_REF] Thiéry | Biological protection against grape berry moths. A review[END_REF]. We adopted a global view of the insect's performance encompassing a large number of fitness-related traits, such as development time, pupal mass, survival rates, and the storage patterns of four energetic compounds. In a wider ecological context, we also focused on the abilities of the caterpillars to survive in agroecosystems when faced with natural enemies, especially parasitoids, by examining larval defensive strategies that involve behavioral defenses (aimed at avoiding parasitoid oviposition) and immune defenses (aimed at killing parasitoid eggs) [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF][START_REF] Vogelweith | Defense strategies used by two sympatric vineyard moth pests[END_REF].

We hypothesized that biological traits included in this study should respond in different ways to our simulation of future climates that might be experienced in the same location. Given its tight dependence on environmental temperature as a pure physiological rate [START_REF] Rebaudo | Modeling temperature-dependent development rate and phenology in insects: review of major developments, challenges, and future directions[END_REF], we expected larval development to be greatly reduced by warming. The thermal response of larval development should in turn determine the time allowed for feeding in this capital breeding species (i.e. only caterpillars feed), thereby negatively impacting pupal mass and energetic reserves. We expected defensive behaviors to display more complex patterns of responses to warming, as the thermal modulation of insect behavior is not purely metabolic, that is, does not only arise from short-term variation in metabolic rates or long-term variation in individual physiological state (e.g. amounts and allocation of energetic reserves) ('kinetic effects', [START_REF] Abram | Behavioural effects of temperature on ectothermic animals: unifying thermal physiology and behavioural plasticity[END_REF]. It also involves intentional behavioral adjustments in response to the perception and the integration of thermal information received by thermosensory organs ('integrated effects', [START_REF] Abram | Behavioural effects of temperature on ectothermic animals: unifying thermal physiology and behavioural plasticity[END_REF]. All of these possible effects were included in our experimental design which sought to investigate the overall impacts of warming on the expression of defensive behaviors to infer the future ability of caterpillars to fend off parasitoids. Finally, we postulated that immunity should be negatively affected by high temperatures because immune function in L. botrana caterpillars is known to peak at a relatively low thermal optimum (22°C or less) [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF].

Material and methods

Thermal regimes

We compared the performance of L. botrana caterpillars experiencing two daily fluctuating thermal regimes representative of current and future conditions occurring in Burgundy, Eastern France (Longvic-Dijon weather station, 47,27°N; 5,09°E; altitude = 219 m) (www.meteofrance.com). We focused on the summer period extending from 15 th July to 15 th August because this one-month period is particularly favorable for L. botrana, as indicated by one peak of activity (adult moths emergence) over this date range [START_REF] Barnay | Survey of natural populations of Trichogramma (Hym., Trichogrammatidae) in the vineyards of Alsace (France)[END_REF][START_REF] Martín-Vertedor | Global warming affects phenology and voltinism of Lobesia botrana in Spain[END_REF]. A curve of current thermal conditions was designed according to a 20-year recording of in situ hourly temperatures (from 1995 to 2014). Based on this curve, we built a mean daily cycle divided into six segments, each lasting 4 h and calculated as the mean segment over the 30 days (15 th July -15 th August) and the 20-year period studied (Table 1). Hereafter, this thermal regime will be referred to as the current regime.

Alongside the current regime, we built the future regime simulating the local conditions that might be found in Burgundy by the end of this century (2081-2100), during the summer period extending from 15 th July to 15 th August. We selected the most pessimistic of the Representative Concentration Pathways scenarios, called RCP 8.5, which predicts the highest positive radiative forcing (i.e. a high absorbance of solar and infrared radiation) associated with massive and growing emissions of greenhouse gas (www.drias-climat.fr).

This scenario was combined with six simulations of high-resolution mesh (12.5 km) applied to the closest point to Dijon (Burgundy). Each simulation was obtained by downscaling a General Circulation Model (GCM) with a Regional Climate Model (RCM) to increase the spatial accuracy of climate predictions. Both GCMs and RCMs are climate tools that enable to follow the evolution of a climate system over time, at different spatial scales: global scale for GCMs, regional or local scale for RCMs nested within GCMs (for more details about the use of climate models in ecology, see [START_REF] Beaumont | Why is the choice of future climate scenarios for species distribution modelling important?[END_REF][START_REF] Ziter | Climate change and voltinism in Californian insect pest species: sensitivity to location, scenario and climate model choice[END_REF]. The six combinations of GCM/RCM used were: CERFACS-CNRM/RCA4, ICHEC-EC-EARTH/RCA4, MPI-ESM-LR/CCLM4, MPI-ESM-LR/REMO019, MPI-ESM-LR/RCA4, MetEir-ECEARTH/RACMO22E. These combinations have been recently used to generate simulations of climate change at small spatial scales across Europe [START_REF] Alfieri | Ensemble flood risk assessment in Europe under high end climate scenarios[END_REF][START_REF] Dosio | Projections of climate change indices of temperature and precipitation from an ensemble of bias-adjusted high-resolution EURO-CORDEX regional climate models[END_REF][START_REF] Kotlarski | Regional climate modeling on European scales: a joint standard evaluation of the EURO-CORDEX RCM ensemble[END_REF]. We used GCMs originating from the Coupled Model Intercomparison Project Phase 5 (CMIP5), a recent multi-model ensemble widely used to produce climate projections in the context of anthropogenic climate change [START_REF] Taylor | An overview of CMIP5 and the experiment design[END_REF]. All the RCMs used to generate downscaled simulations came from the Coordinated Regional Climate Downscaling Experiment across Europe (EURO-CORDEX) and were adapted to downscale the outputs of the GCMs used [START_REF] Dosio | Projections of climate change indices of temperature and precipitation from an ensemble of bias-adjusted high-resolution EURO-CORDEX regional climate models[END_REF][START_REF] Jacob | EURO-CORDEX: new high-resolution climate change projections for European impact research[END_REF]. All data are available on the Drias portal (www.drias-climat.fr). For each simulation, daily maximum and minimum air temperatures were extracted. We then generated six future mean daily cycles (one for each simulation) based on simulated maximum and minimum temperatures and the present daily cycle. The future regime, as the current regime, was composed of six segments of 4 h, each calculated as the mean segment over the six simulations performed (Table 1). Comparison between current and future regimes reveals that global warming should increase both the mean temperature (+ 5.3°C) and the daily thermal range (+ 0.6°C) in our focal area (Table 1).

Table 1 Temperature conditions (°C) for the two daily fluctuating regimes used in this study: the current regime and the future regime, each divided into 6 segments of 4 h. Daily thermal range is defined as the difference between maximum and minimum daily temperatures.

Current regime

Insect stock and larvae collection

We used larvae originating from an inbred and diapause free strain of L. botrana maintained at the French National Institute for Agricultural Research (INRA, Villenave d'Ornon, France)

for several years under controlled conditions. This stock consists of a large number of caged adults (several thousand per week), to which wild individuals were regularly added to preserve genetic diversity. Hence, larvae coming from this artificial stock display similar patterns of defensive behaviors and basal immunity compared with wild individuals collected in French vineyards [START_REF] Vogelweith | Defense strategies used by two sympatric vineyard moth pests[END_REF]. Moths were reared under standard conditions (20 ± 0.5°C, 60 ± 5% relative humidity, photoperiod of L17: D6 and 1 h of dusk). Luminosity was 600 lx during photophase and 100 lx at dusk. Two bands of waxed paper were provided as a support for oviposition. Every 2 days, these papers were renewed and transferred to a plastic box covered by a moist piece of paper towel to avoid egg desiccation until hatching.

A total of 2246 freshly-hatched larvae (aged < 24 h) were collected throughout the experiments with a fine brush and individually reared in Eppendorf tubes filled with 1.5 ml of artificial medium (composition for 1000 ml: 1000 ml water, 15 g agar, 86.6 g maize flour, 41.3 g wheat germ, 45.5 g beer yeast, 6 g ascorbic acid, 3.4 g mineral salt, 0.32 g Scala ® , 2.7 g benzoic acid, 2.8 g Nipagin ® and 5 ml 95% ethanol) [START_REF] Thiéry | Relative performance of European grapevine moth (Lobesia botrana) on grapes and other hosts[END_REF]. Neonate caterpillars were isolated in tubes so that no larval competition could occur and introduce an experimental bias [START_REF] Thiéry | Larval intraspecific competition for food in the European grapevine moth Lobesia botrana[END_REF]. Tube caps were pierced and covered by a piece of fine mesh fabric to allow air circulation while preventing larvae from escaping. Individuals were randomly assigned to two incubators (ST 2/2 BASIC, Pol-Eko Aparatura), each simulating one of the two thermal regimes described above (temperature ± 0.1°C, 50 ± 10% relative humidity, L18: D6, 650 lx). In order to avoid a potential incubator effect, larvae and their associated thermal regime were switched between climate chambers two times a week, as well as the location of individuals inside the new incubator. Temperatures within the climate chambers were tracked weekly with an independent data logger (Hobo, Onset Computer Corporation), and did not deviate from the thermal regimes programmed during the whole course of the experiments. Larval development was surveyed when caterpillars were swapped between incubators (i.e. two times a week) to minimize disturbance. Once they reached their fifth -and final -instar stage, larvae were randomly assigned to one of three experimental groups all along the experiments, because the different measurements of biological traits involved in this study cannot be taken on a single individual. We focused on the fifth instar because the energetic resources accumulated during the whole larval stage can be quantified at this late larval instar that directly precedes pupation. In addition, measurements of behavioral and immune defenses against parasitoids are classically performed at the end of larval development in this species [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF][START_REF] Vogelweith | Defense strategies used by two sympatric vineyard moth pests[END_REF]. In Group 1, the fifth instar larvae were left until pupation in order to measure development time, pupal mass, survival from first instar larva to adult stage, and sex ratio. In Group 2, the fifth instar larvae were frozen and stored to quantify later their energy budgets. In Group 3, the behavioral and immune traits involved in defense of fifth instar caterpillars against larval parasitoids were measured.

Group 1: development time, pupal mass, survival and sex ratio

A total of 2043 freshly hatched larvae were initially assigned to Group 1 in order to develop until pupation (n = 981 individuals for current regime, n = 1062 individuals for future regime). We recorded the time (in days) elapsed between hatching and pupation (i.e. the development time of the larval stage), which corresponds to the time during which caterpillars are able to feed. The pupae were collected carefully with fine forceps and weighed (± 0.1 mg) with a balance (Pioneer PA214C, OHAUS). Development time and pupal mass were only recorded for individuals that reached the adult stage to discriminate the results between males and females, which were sexed upon emergence. We also calculated survival (number of emerged adults relative to the number of freshly hatched larvae initially assigned to each thermal regime), and sex ratio (expressed as the proportion of males in the adult population).

Group 2: energetic assessments

These measurements initially involved 59 fifth instar larvae (n = 29 for current regime, n = 30 for future regime). Caterpillars were cleaned with a fine brush to remove any residual of artificial medium from the surface of their body, transferred to Eppendorf tubes, frozen in liquid nitrogen and kept at -80°C for latter quantification of their energy budgets. They were subsequently weighed to obtain fresh body mass (± 0.01 mg) with a microbalance (Quintix 35-15, Sartorius), before being crushed with stainless steel beads (tubes shaken for 90 s at 25

Hz) in 180 µl of aqueous lysis buffer solution (composition: 100 mM KH2PO4, 1 mM dithiothreitol DTT, 1 mM ethylenediaminetetraacetic EDTA, pH = 7.4). Biochemical assays were run on four metabolites potentially involved in energy production: proteins, lipids, soluble carbohydrates and glycogen. The total amount of soluble proteins available was estimated using a DC Protein Assay kit (Bio-Rad). We used the spectrophotometry method described by [START_REF] Foray | A handbook for uncovering the complete energetic budget in insects: the van Handel's method (1985) revisited[END_REF] for the quantification of lipids, soluble carbohydrates and glycogen.

Crushed samples were placed on ice for 30 min to ensure proteins solubilization, centrifuged (4000 g, 5 min, 4°C) and 5 µl of supernatant from each sample were pipetted to microplate wells together with 35 µl of lysis buffer to obtain diluted samples. Particular attention was paid to avoid collecting lipids (which often form a thin surface layer on the top of the sample) when pipetting the 5 µl of supernatant for protein assays, because lipids might disturb the absorbance readings in the Bradford approach used to quantify proteins [START_REF] Foray | A handbook for uncovering the complete energetic budget in insects: the van Handel's method (1985) revisited[END_REF]. Then, 5µl of these diluted samples were transferred to new microplate wells and supplemented with 225 µl of Bradford micro-assay reagent (DC Protein Assay Kit, Bio-Rad).

Reaction was allowed to proceed for 15 min at room temperature, after which absorbance readings were taken at 750 nm. Protein concentration in the samples was estimated with a standard curve based on a dilution-series of bovine gamma globulin standard (Pierce, Thermo Fisher Scientific) dissolved in lysis buffer. This dilution-series was constituted by the following protein concentration values: 0, 0.062, 0.125, 0.25, 0.5, 1 and 2 mg.ml -1 . Finally, 5

µl of lysis buffer, 20 µl of 20 % sodium sulphate solution and 1.5 ml of chloroform-methanol mixture (1:2 v/v) were added to each crushed sample to solubilize total lipids and watersoluble carbohydrates. These samples were then conserved at room temperature for 24h before biochemical assays of the amounts of lipids, soluble carbohydrates and glycogen.

At the end of this 24h duration, homogenates were centrifuged at room temperature (4800 g, 6 min). Centrifugation enabled to isolate lipids and soluble carbohydrates (supernatant) from glycogen (pellet). Determination of lipid body amount was performed with a colorimetric method involving vanillin reagent (Alfa Aesar, Thermo Fischer Scientific). For each centrifuged sample, 75 µl of supernatant were transferred to an Eppendorf tube and heated at 90°C until complete solvent evaporation. Then, each tube was supplemented with 40 µl of 95-98% sulphuric acid and incubated at 90°C for 10 min. For lipids revelation, 960 µl of vanillin solution (composition: 100 ml ultrapure water, 400 ml 85% orthophosphoric acid, 600 mg vanillin) were then deposited in each tube. After vigorous vortexing, 200 µl of each tube were pipetted to microplate wells for absorbance measurements, which were taken at 525 nm. The dilution-series used to assess lipid concentration in the samples involved glyceryl trioleate as a standard (Sigma-Aldrich) dissolved in chloroform, and was comprised by the following concentration values: 0, 2.5, 5, 10, 20, 40 and 80 µg.ml -1 . The body amounts of both soluble carbohydrates and glycogen were determined with a colorimetric method based on anthrone reagent (Alfa Aesar, Thermo Fisher Scientific). For soluble carbohydrates, 750 µl of supernatant from each centrifuged sample were collected and deposited in an Eppendorf tube, before being allowed to fully evaporate at 95°C. For glycogen, the remaining supernatant in the centrifuged samples was removed and the pellet was left at room temperature during 30 min for complete solvent evaporation. Then, 2 ml of anthrone solution (composition: 150 ml ultrapure water, 380 ml 95-98% sulfuric acid, 750 mg anthrone) were added to each tube (containing either soluble carbohydrates or glycogen), and all these tubes were heated at 95°C for 17 min. Tubes were subsequently vortexed and 200 µl of each were withdrawn and deposited in microplate wells before readings of optical density, which were performed at 625 nm. The concentration of these two energetic compounds in the samples was estimated through comparison with a dilution-series constituted by the following concentration values of glucose (Sigma-Aldrich): 0, 6.25, 12.5, 25, 50, 100, 200 and 400 µg.ml -1 .

For proteins and lipids, two replicates were performed and individuals for which the coefficient of variation exceeded 30% were excluded from further analysis. Repeatability was relatively high, as indicated by the low percentages of individuals removed from the protein (8.5%) and the lipid datasets (5.1%). At the end of this selection procedure, we retained 54 larvae from the protein dataset (n = 27 for current regime, n = 27 for future regime) and 56 larvae from the lipid dataset (n = 29 for current regime, n = 27 for future regime).

Group 3: behavioral and immune defenses

A total of 144 fifth instar larvae were assigned to measurements of defensive traits (n = 73 individuals for current regime, n = 71 individuals for future regime). Three successive behaviors were quantified, always in the same order ('flee', 'twisting' and 'dropping'), in accordance with the sequence involved in defense against larval parasitoids in natural conditions [START_REF] Vogelweith | Defense strategies used by two sympatric vineyard moth pests[END_REF]. Additionally, these behavioral tests were performed at an ambient temperature strictly identical to the mean temperature of the regime considered: 20.5°C if the tested individual was reared in current regime, or 25.8°C if it was reared in future regime (Table 1). Temperature in the testing rooms was controlled with Hobo data loggers. After the completion of each behavioral test, 20 min of rest were given to each larva in a clean Eppendorf tube drilled to allow air circulation before the next test started.

The first behavior studied, called 'flee', refers to larvae escape ability by moving away from a generic threat without leaving the bunch they feed on. Here, we estimated the locomotor activity (movement speed) of caterpillars as a proxy of 'flee' behavior, to infer their ability to evade parasitoids in natural conditions. For this purpose, caterpillars were installed on a plastic squared sheet (84 x 116 cm, squares size: 1 x 1 cm) and acclimated for 30 s under the lid of a Petri dish. The lid was then removed and each larva was observed to count the total number of lines crossed during 60 s (the minimum duration required by a larva to exit the sheet). As this behavior occurs before physical contact between the caterpillar and the parasitoid, no simulation of a parasitoid attack was needed to cause the larvae to flee.

Locomotor activity was naturally induced by the stress associated with the manipulation of caterpillars with a fine paintbrush during the extraction from their rearing tube, and their exposure to a new environment during behavioral tests.

The second behavior, 'twisting', consists of multiple and rapid torsions in response to contact between a larva's body and a parasitoid sting. We mimicked a parasitoid attack by touching the dorsal part of the caterpillar with a fine brush, after 30 s of acclimation under the lid of a Petri dish. Each individual was touched four times in 1 min. The entire sequence was video recorded (HDR-CX220E, Sony) and further analyzed in slow motion with Kinovea 0.8.15 software to score the total number of torsions over the four touches.

Finally, we examined 'dropping' behavior, which describes how caterpillars faced with a foraging parasitoid can drop and weave a silk thread to return to their living patch once the parasitoid has left it. Larvae were installed at the top of a 150 cm high bracket. After an acclimation of 30 s under a reversed Eppendorf tube, each larva was touched with a fine brush (as described in the previous paragraph) until it fell. For caterpillars weaving a thread, we measured its length with a ruler (precision ± 3 mm) after 5 s of stabilization. Thread length is supposed to be positively linked to larval escape ability [START_REF] Vogelweith | Defense strategies used by two sympatric vineyard moth pests[END_REF].

Once the three behavioral tests were carried out, larvae were returned to their rearing tube and associated thermal regime for 3 h before the immune measurements were taken. The ability of the larvae to kill parasitoid eggs was estimated by measuring hemocyte concentration and activity of the phenoloxidase (PO). Hemocytes are immune cells that freely circulate in hemolymph of insects and bind to parasitoid eggs. Hemocytes release the PO enzyme that catalyzes melanization reactions occurring around parasitoid eggs as part of the immune response [START_REF] Lavine | Insect hemocytes and their role in immunity[END_REF]. Caterpillars were not challenged prior to these immune tests, because they naturally display high levels of basal immunity and do not significantly respond to an infection [START_REF] Vogelweith | Defense strategies used by two sympatric vineyard moth pests[END_REF]. Larvae were chilled on ice for 30 min and then photographed using a stereomicroscope at 12.5x magnification (Stemi 508, Zeiss) to measure the distance between the most distant margins of the head capsule (precision: ± 0.1 µm) as a reliable estimator of larval body size [START_REF] Delbac | Larval instars determination for the European 37 grapevine moth (Lepidoptera: Tortricidae) based on the frequency distribution of headcapsule widths[END_REF]. For this experimental group, we measured larval body size rather than body mass since body size is known to correlate with some of the larval defenses in this species [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF] and because caterpillars cannot be accurately weighed while alive [START_REF] Muller | Immune benefits from alternative host plants could maintain polyphagy in a phytopagous insect[END_REF]. One 2 µl sample of hemolymph was then collected from a prick in the dorsal part of the abdomen with a cold sterile glass capillary (Hirschmann Laborgeräte, Eberstadt). This sample was diluted in 20 µl of cold phosphate-buffered saline (PBS, 8.74 g NaCl, 1.78 g Na2HPO4, 1000 ml distilled water, pH 6.5). A volume of 10 µl of this solution was immediately withdrawn to estimate hemocyte concentration with a Neubauer improved hemocytometer under a phase contrast microscope at 400x magnification (Primo Star, Zeiss). The remaining 12 µl of diluted hemolymph were supplemented with 10 µl of PBS. These samples were frozen in liquid nitrogen and stored at -80°C for the latter estimation of PO activity.

We distinguished between functional PO naturally activated in hemolymph (PO activity) and total PO including functional PO and proenzymes (total PO activity). These measurements were based on the spectrophotometry method described by [START_REF] Vogelweith | Immunocompetence increases with larval body size in a phytophagous moth[END_REF]. Hemolymph samples were allowed to thaw very slowly on ice and centrifuged ( 4000g, 15 min, 4°C) before 5 µl of supernatant were transferred to microplate wells. These samples were supplemented with either 160 µl of diluted PBS solution (35 ml ultrapure water, 5 ml filtered PBS) for PO activity measurement, or with 160 µl of chymotrypsin solution (35 ml ultrapure water, 5 ml filtered PBS, 2.45 mg trypsin) for total PO activity measurement.

Finally, 20 μl of L-Dopa solution (40 ml ultrapure water, 160 mg L-Dopamine) were deposited in each well as a colorimetric substrate. An enzymatic reaction proceeded for 40 min at 30°C in a microplate reader (Versamax, Molecular Devices), during which the readings were taken every 15 s at 490 nm. Data were subsequently analyzed with the SOFT-Max Pro 4.0 software. We recorded maximum enzyme activity (Vmax), corresponding to the slope of the absorbance curve during its linear phase. All immune assessments were reported to 1 µl of pure hemolymph.

Statistical analyses

Development time and pupal mass were normally distributed and displayed homogenous variances (homoscedasticity) between thermal regimes and sexes. Consequently, they were analyzed by means of two-way Analyses of Variance (ANOVAs) integrating thermal regime, sex and their interaction. Survival and sex ratio were expressed in proportions and therefore compared among thermal regimes with Generalized Linear Models (GLMs)-binomial error.

To control for allometric effects on larval physiological and behavioral traits, we included either larval body mass (for energetic reserves) or larval body size (for defensive behaviors and immunity) as a covariate in the statistical models, alongside thermal regime as an explanatory variable. Most of the data were normally distributed (the reserves of the four energetic compounds, hemocyte concentration, total PO activity) or required a logarithm transformation to satisfy normality assumption (thread length and PO activity), and their variances were homogenous between thermal regimes. Accordingly, all these data were studied with analyses of covariance (ANCOVAs) testing for homogeneity of slopes and intercepts, as these models integrated the effects of the explanatory variable (thermal regime), the associated covariate (larval body mass or larval body size) and their interaction. As overdispersed count data, the number of lines caterpillars crossed and the number of twists were analyzed with GLM-negative binomial error. Normality and homoscedasticity were assessed with a Shapiro-Wilk and a Levene test, respectively. For count data, overdispersion (observed variance greater than the theoretical one predicted by the fitted model) was detected with a postregression likelihood ratio test [START_REF] Cameron | Regression-based tests for overdispersion in the Poisson model[END_REF]. All statistical analyses were carried out using R 3.5.2 software.

Results

Group 1: development time, pupal mass, survival and sex ratio

Neither development time (two-way ANOVA: F1,832 = 0.04, P = 0.84) nor pupal mass (twoway ANOVA: F1,832 = 0.39, P = 0.53) was impacted by the interaction between thermal regime and sex. Development time was modulated by thermal regime (F1,832 = 639, P < 0.001) and sex (F1,832 = 26.5, P < 0.001) in an additive way: individuals reared in future, warmer conditions needed less time to complete their larval development than those reared in current, cooler conditions, and females developed slower than males (Table 2). Pupal mass was affected by sex (F1,832 = 1308, P < 0.001) but not by thermal regime (F1,832 = 0.67, P = 0.41), as females being significantly heavier than males (Table 2). Survival was influenced by thermal regime (GLM-binomial error: = 10.6, P < 0.001): larvae reared in warmer conditions were more prone to survive until the adult stage than those held in cooler conditions (Table 2). Adult sex ratio did not differ between thermal regimes (GLM-binomial error: = 0.02, P = 0.88) (Table 2).

Table 2 Mean values and 95% confidence intervals of development time (time between egg hatching and pupation), pupal mass, survival (from larval to adult stage), and sex ratio (proportion of males in the adult population) for the two thermal regimes. Different letters indicate significant differences for a given trait (P < 0.05).

Current regime

Group 2: energetic assessments

None of the four energetic compounds was affected by the interaction between thermal regime and larval body mass (Table 3). Among these compounds, only the body amount of lipids was influenced by thermal regime, while the amounts of proteins, soluble carbohydrates and glycogen remained the same across thermal regimes (Table 3, Fig. 1A,B,C,D).

Caterpillars reared in warmer conditions stocked less lipid reserves at the end of their larval development relative to their counterparts reared in cooler conditions (Fig. 1B). Protein and lipid body amounts were both affected positively by larval body mass (

Group 3: behavioral and immune defenses

None of the behavioral or immune traits was impacted by the interaction between thermal regime and larval body size (Table 4). Among the behavioral traits examined, only the number of lines crossed by caterpillars during 'flee' tests was influenced by thermal regime: larvae reared and tested at warmer conditions crossed significantly more lines relative to individuals originating from cooler conditions (Table 4, Fig. 2A). Thermal regime did not affect 'twisting' (number of twists) and 'dropping' (length of the silk thread woven) behaviors (Table 4, Fig. 2B,C). From an immunological perspective, hemocyte concentration and PO activity were not impacted by thermal regime (Table 4, Fig. 3A,B). However, total PO activity was significantly modulated by thermal regime: larvae reared in warmer conditions displayed lower levels of total PO activity compared with those held in colder conditions (Table 4, Fig. 3C). None of the behavioral and immune traits was modulated by larval body size (Table 4). Such a diversity of thermal responses among traits strengthens the importance of an integrative approach involving measurements on a wide array of traits to accurately forecast the consequences of global warming for an organism's performance, and the way it will interact with adjacent trophic levels. Some traits related with population dynamics were positively affected by rising temperatures, presumably indicating an overall increase in caterpillars' performance under a simulated global warming scenario. Indeed, caterpillars experiencing higher, future temperatures developed faster and showed increased survival rates compared with individuals kept under thermal conditions similar to those currently recorded in Eastern France. These findings remain in accordance with previous studies showing that the thermal optimum for the development of L. botrana larvae -including the laboratory strain used in this study -ranges from 28°C to 30°C [START_REF] Briere | Comparison of temperature-dependent growth models with the development of Lobesia botrana (Lepidoptera: Tortricidae)[END_REF][START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF]. Hence, the experimental warming applied here (mean temperature increasing from 20.5 to 25.8°C) positively impacted development rates by bringing environmental temperatures closer to the thermal optimum of L. botrana. Similarly to a previous work conducted on the same species [START_REF] Thiéry | Relative performance of European grapevine moth (Lobesia botrana) on grapes and other hosts[END_REF], we found that faster development was accompanied with higher survival rates. One plausible explanation to these results could involve a phenomenon known as 'developmental resistance', whereby disease resistance usually increases throughout larval stages in some butterfly species [START_REF] Mcneil | Contributions of immune responses to developmental resistance in Lymantria dispar challenged with baculovirus[END_REF][START_REF] Shikano | Jasmonic acid-induced plant defenses delay caterpillar developmental resistance to a baculovirus: slow-growth, high-mortality hypothesis in plant-insect-pathogen interactions[END_REF]. Hence, caterpillars may benefit from a faster development under warmer conditions by spending shorter in the early ontogenetic stages, which are the most susceptible to mortality driven by pathogenic infections [START_REF] Valadez-Lira | Comparative evaluation of phenoloxidase activity in different larval stages of four lepidopteran pests after exposure to Bacillus thuringiensis[END_REF].

As a capital breeding species, we would have expected L. botrana individuals to incur costs arising from a shrunk larval stage (i.e. a reduced time allowed for feeding) in warmer conditions, especially regarding pupal mass. Contrary to these initial expectations, pupal mass did not differ between thermal regimes. These results confirm that L. botrana caterpillars could compensate for a shortened feeding period under hotter conditions through an increase in daily gain of body mass (i.e. growth rate) [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF]. The underlying mechanisms to support a high growth rate in warm conditions could involve an increased food intake rate and/or an enhanced efficiency at converting food into body matter when exposed to hotter conditions [START_REF] Bauerfeind | Increased temperature reduces herbivore host-plant quality[END_REF][START_REF] Lee | Temperature-by-nutrient interactions affecting growth rate in an insect ectotherm[END_REF][START_REF] Lemoine | Variable effects of temperature on insect herbivory[END_REF].

Nonetheless, the 26% decrease in the body amounts of lipids observed in warmer conditions seems to indicate that larvae cannot compensate for the effects of warming on energetic budgets, with costs being specifically apparent on fat reserves (the three other energetic compounds remaining unaffected by temperature). Interestingly, previous work also recorded a reduced lipid storage efficiency for fast developing caterpillars in Spodoptera exigua (Lepidoptera: Noctuidae), suggesting that high development rates induced by warming may be accompanied with a decline in lipid reserves [START_REF] Lee | Temperature-by-nutrient interactions affecting growth rate in an insect ectotherm[END_REF]. These findings indicate that the lipid energetic compartment could be particularly susceptible to the detrimental effects of a reduced feeding duration caused by an accelerated development under warmer conditions.

Aside from traits related with population dynamics, thermal conditions modulated the expression of several defensive traits involved in trophic interactions between L. botrana caterpillars and their natural enemies, especially the guild of parasitoids. Concerning behavioral traits, it is not possible to identify the mechanisms underlying the thermal response of 'flee' behavior at this stage. It may arise from long-term effects, whereby temperature met throughout larval development might have impacted the physiological state of caterpillars and their resource partitioning between competing defensive traits [START_REF] Abram | Behavioural effects of temperature on ectothermic animals: unifying thermal physiology and behavioural plasticity[END_REF]. It could also be attributable to short-term effects related with temperature prevailing during behavioral tests, which might have influenced caterpillars' metabolic rates and/or triggered thermosensory processes leading to behavioral adjustments following perception of heat conditions [START_REF] Abram | Behavioural effects of temperature on ectothermic animals: unifying thermal physiology and behavioural plasticity[END_REF][START_REF] Soto-Padilla | Thermosensory perception regulates speed of movement in response to temperature changes in Drosophila melanogaster[END_REF]. In terms of trophic dynamics, our findings indicate that increasing temperatures should enhance the ability of L. botrana caterpillars to escape from natural enemies through upregulation of 'flee' behavior. This does not, however, necessarily imply a lower larval susceptibility to parasitism, provided that the behaviors specifically expressed in case of an attempt of parasitoid oviposition ('twisting' and 'dropping') remained unaffected by thermal conditions.

Concerning immune traits, total PO activity was the only immune trait affected (negatively) by temperature, congruently with a previous work on L. botrana [START_REF] Iltis | When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest[END_REF] and our hypothesis that global warming could induce immunosuppressive effects in larvae of this species. Intriguingly, the decrease in total PO activity was not explained by a concomitant lowering of hemocyte concentration, which remained constant across thermal treatments in our study. Hemocyte populations are composed by different cell types (four types have been identified in larvae of the moth Eupoecilia ambiguella, a relative of L.

botrana), each having a particular role in immunity [START_REF] Lavine | Insect hemocytes and their role in immunity[END_REF][START_REF] Vogelweith | The relative abundance of hemocyte types in a polyphagous moth larva depends on diet[END_REF]. In this regard, we could postulate that thermal conditions might influence the relative abundances of hemocyte types in L. botrana larvae, tending to decrease the proportion of cells involved in synthesis of PO zymogens (e.g. oenocytoids). Our findings also indicate that, despite no effect on basal immunity (PO activity), warming could significantly reduce the ability of L. botrana caterpillars to respond to a parasitic infection because hotter rearing conditions decreased total PO activity. Indeed, the activation of PO cascade system is required to catalyze melanization of parasitoid eggs (González-Santoyo and Córdoba-Aguilar, 2012; [START_REF] Kanost | Phenoloxidases in insect immunity[END_REF]. However, it is worth noting that, in our immunological assays, immune reactions were allowed to proceed at standard temperature.

Considering that, in lepidopteran species, the kinetics of PO enzyme will likely increase alongside larval body temperature up to a certain limit [START_REF] Xue | Enzymatic properties of phenoloxidase from Pieris rapae (Lepidoptera) larvae[END_REF], it remains possible that larvae reared in warmer conditions invested less in the production of the active form of PO as an adaptive choice to keep the overall enzymatic activity constant across temperatures.

Further insights into the functional consequences of this variation in larval immunity -for instance by measuring the in vivo ability of caterpillars to encapsulate and melanize foreign bodies at different temperatures -would be highly valuable to predict more thoroughly the impacts of global warming on caterpillars' survival in context of high parasitism pressure as recorded in vineyards.

Conclusion

In summary, our study brings new lines of evidence to suggest that multiple traits in a given species may differ in their sensitivity to global warming, underlying complex consequences for population dynamics and trophic interactions. Here, we found that, in terms of population dynamics, warming brought L. botrana closer to its thermal optimum for larval development.

This should lead to a shorter generation time and therefore a higher future voltinism (number of generations per growing season) of L. botrana in Eastern France, as recently observed in meridional areas [START_REF] Martín-Vertedor | Global warming affects phenology and voltinism of Lobesia botrana in Spain[END_REF]. To what extent these benefits might be mitigated by the reduction of lipid reserves observed under warmer conditions remains not well appreciated for now. A decline in lipids stock might, for instance, negatively impact the survival of the naturally diapausing generation of L. botrana, because fat reserves are crucial to survive extended non-feeding periods [START_REF] Sinclair | The many roles of fats in overwintering insects[END_REF]. It may also persist into the adult stage and adversely impact adult dispersal ability and reproduction [START_REF] Vande Velde | Lipid economy, flight activity and reproductive behaviour in the speckled wood butterfly: on the energetic cost of territory holding[END_REF]. Finally, we found that key traits involved in the trophic interactions between L. botrana caterpillars and their larval parasitoids were altered by warming. At this stage, predicting the consequences for future larval mortality induced by natural enemies in agroecosystems is somewhat challenging, provided that the direction of the effect of warming differed among defensive traits, and that parasitoids will also be impacted by rising temperatures, from both physiological and behavioral perspectives [START_REF] Hance | Impact of extreme temperatures on parasitoids in a climate change perspective[END_REF].

Several considerations should, however, be carefully examined to provide a more integrated picture of the impacts of warming for L. botrana, with respect to its evolutionary and ecological context. First, our study specifically investigated the plastic response occurring within one generation of L. botrana larvae exposed to an abrupt environmental warming. In natural conditions climate disturbance will more likely translate into a gradual shift in thermal conditions whose effects will spread across insect life stages and generations. For this reason, it is now widely acknowledged that the response of insect species to global warming will not solely be determined by intragenerational plasticity, but also by transgenerational plasticity (whereby temperatures faced by one generation will influence the expression of a phenotype in the subsequent generations) in concert with evolutionary processes [START_REF] Donelson | Transgenerational plasticity and climate change experiments: where do we go from here?[END_REF][START_REF] Sgrò | What can plasticity contribute to insect responses to climate change?[END_REF]. It would therefore be worth investigating whether these different types of response might interact to shape the insect phenotype when experiencing gradual warming over several successive generations. Second, to what extent the mosaic of microclimatic conditions existing at the vine plant and grape bunch levels might create opportunities for

Fig. 1

 1 Fig. 1 Effect of thermal regime (circles and solid lines: current regime, triangles and dashed

Fig. 3

 3 Fig.3Effect of thermal regime on the mean (± 95% c.i.) of hemocyte concentration (A),

  of global warming, we here examined the responses of different fitness-related traits in caterpillars of the moth L. botrana to realistic daily fluctuating regimes reflecting current and future conditions in Eastern France. Many of the traits inspected were affected by our experimental imitation of climate change. Warming positively influenced caterpillars' development (leading to a 31% reduction in the time needed to complete all five larval instars), survival from first instar larva to adult stage (+19%) and larval ability to escape natural enemies through the expression of 'flee' behavior (+60%). Conversely, rising temperatures led to depletion of lipid reserves (-26%) and reduced total PO activity (-34%).

Table 3 ,

 3 Fig. 1A, B): heaviest larvae accumulated more reserves than lightest ones (proteins: slope = 44.1; lipids: slope = 32.1).were studied with analyses of covariance testing for homogeneity of slopes and intercepts. Bold values indicate significant effects (P < 0.05).

	432
		Thermal regime	Larval body mass	Regime * Body mass
		Test value	P	Test value	P	Test value	P
	Proteins	F1,50 = 1.72	0.20	F1,50 = 50.0	< 0.001	F1,50 = 0.001	0.98
	Lipids	F1,52 = 5.69	0.02	F1,52 = 5.34	0.02	F1,52 = 1.63	0.21
	Soluble carbohydrates	F1,55 = 0.03	0.86	F1,55 = 1.50	0.23	F1,55 = 1.64	0.20
	Glycogen	F1,55 = 2.36	0.13	F1,55 = 1.98	0.16	F1,55 = 0.52	0.47

Table 4

 4 Effects of thermal regime, larval body size (head capsule width) and their interaction on different defensive behaviors and immune traits involved in defenses of caterpillars against larval parasitoids. Bold values indicate significant effects (P < 0.05). Effect of thermal regime on the mean (± 95% c.i.) of the number of lines crossed by larvae during 'flee' tests (A), the number of twists over four touches (B), and the length of the silk thread spun (C). Asterisks highlight significant differences (*** P < 0.001, ** P < 0.01, * P < 0.05, n.s. non-significant) and numbers refer to sample sizes.

	Thermal regime	Larval body size	Regime * Body size
	Test value	P	Test value	P	Test value	P

Acknowledgements

We gratefully acknowledge L. Delbac who managed the insect stock and E. Parfitt for English revision. We also want to thank L. Chevallier, P. Hübner, R. Kuzmin, M. Pêcheur, R.

Quinaux and A. Rathery for their practical help in the experiments.

Funding

This work was supported by the Conseil Régional de Bourgogne Franche-Comté (PARI, FABER LOUAPRE-AGREE-BGS and VALEACLIM-BOIS), and the European Union (PO FEDER-FSE Bourgogne 2014/2020 programs).

larval behavioral thermoregulation (through microsite selection) to alleviate the effects of warming must be taken into consideration. Apparently homogenous landscapes are actually composed of an important diversity of thermal conditions at much smaller, biologically relevant spatial scale matching the body size of the insect [START_REF] Potter | Microclimatic challenges in global change biology[END_REF][START_REF] Terblanche | Physiological variation of insects in agricultural landscapes: potential impacts of climate change[END_REF]. Thus, variation in air temperature recorded in a given site at a macroclimatic scale may bear little relationship to the variation in the operative body temperature of the insect experiencing a set of contrasting microclimatic conditions. In vineyards, grape berry temperature displays an important variability both between grape bunches and within a single bunch, in relation with factors determining direct solar radiation (e.g. bunch exposure, shading provided by leaf canopy), bunch compactness and architecture [START_REF] Haselgrove | Canopy microclimate and berry composition: the effect of bunch exposure on the phenolic composition of Vitis vinifera L cv. Shiraz grape berries[END_REF][START_REF] Moosavi | Effects of grapevine bunch exposure to sunlight on berry surface temperature and Lobesia botrana (Lepidoptera: Tortricidae) egg laying, hatching and larval settlement[END_REF][START_REF] Tello | What do we know about grapevine bunch compactness? A state-ofthe-art review[END_REF]. Small scale variation in berry temperature due to sunlight exposure has been shown to deeply impact L. botrana performance, particularly in the early ontogenetic stages (egg hatching, larval settlement) (Kiaeian [START_REF] Moosavi | Effects of grapevine bunch exposure to sunlight on berry surface temperature and Lobesia botrana (Lepidoptera: Tortricidae) egg laying, hatching and larval settlement[END_REF]. Incorporating this natural thermal complexity at microhabitat scales and the way it would be altered by a rapidly changing climatic context could therefore become a next step towards a more thorough understanding of the consequences of global warming for this insect pest.

Competing interests

The authors declare no conflict of interests.

Global warming

Vineyards