text:
Cécile Allard
email: cecile.allard@u-pec.fr

Edith Petitfour
email: edith.petitfour@univ-rouen.fr

Learning to use a protractor: Touch screen tablet or not?

Keywords: Practice, protractor, language, angle, touch screen tablet

In the present study, we compare the practice of one teacher in two 5 th -grade classes for the same teaching concept (about angles) according to different working arrangements. In one of her classes, the teacher combines lecturing and interactive class: she talks and she exposes knowledge in front of her students. In the second class, she decides to try a new working arrangement: the flipped classroom. We compare the knowledge at stake by studying actions, gestures and language when video lectures are used on the one hand and when such devices are not used on the other hand. Thus, we compare the knowledge, which was shared and discussed in the classroom.

Introduction

Our goal is to study the impact of the working arrangements' modifications (use of the touch screen tablet or not) about knowledge exposure [START_REF] Allard | Analysis of teachers' practices: The case of fraction teaching at the end of primary school in France[END_REF]. More specifically, we study the geometric knowledge exposure when the students learn to use an instrument (the protractor). We think that the use of artifacts have a contribution at the cognitive level [START_REF] Bartolini Bussi | Semiotic mediation in the mathematics classroom: artifacts and signs after a Vygostkian perspective[END_REF].Thus learning to use a protractor contributes to the construction of the angle's concept. This paper focuses on the teaching and learning of the angle's concept. It involves one teacher, Marie, and her grade 5 students in their use of the protractor. In France, at primary school level, students learn how to compare angles and how to reproduce a given angle using templates or tracing paper. In 5 th grade they are then trained to use a protractor to measure angles and to construct an angle with a given measurement.

For several years, ministry of education recommends the use of new technologies and more recently emphasizes the need to individualize teaching: the flipped classroom may provide the means to meet these demands. This model of classroom instruction can be defined as an educational technique that consists of two parts: interactive group learning activities inside the classroom, and direct computerbased individual instruction outside the classroom [START_REF] Bishop | The flipped classroom: A survey of the research[END_REF].

Theoretical framework

This qualitative study is built on prior work on the Double Approach by Robert & Rogalski (2005), current work on the concept of angle and on the study of actions with instruments [START_REF] Petitfour | Enseignement de la géométrie à des élèves en difficulté d'apprentissage : étude du processus d'accès à la géométrie d'élèves dyspraxiques visio-spatiaux lors de la transition CM2-6 ème[END_REF].

About practice

To analyse and interpret teacher's practices, we use the theory of the Double Approach defining five components: personal (teacher's choices, beliefs), social (teachers' working place, their colleagues and the social environment of their students, in both disadvantaged and advantaged areas), institutional (curriculum, relationship with supervisors), cognitive (choices about mathematical contents, tasks, organization and forecasts on how to manage the session) and mediative (improvisations, speeches, motivation of the students' participation, devolution of instruction and knowledge exposures). The study of the students' activities allows to give information on cognitive and mediative components (what students did, what they said about their activities and what they learnt). Consequently, we have to clarify the elements of knowledge at stake, misconceptions and difficulties in the learning of the concept of angle.

About angle

Angle appears to be a very complex and multifaceted concept, which can be defined in three different aspects: turn (an amount of turning between two lines meeting at a point), ray (a union of two rays with a common end point) and region (the intersection of two half-planes) [START_REF] Mitchelmore | Development of angle concepts: A framework for research[END_REF].

Students encounter numerous difficulties in the learning of angles and misconceptions have been pointed out in several experimental studies (Berthelot & Salin, 1995;[START_REF] Mitchelmore | Development of angle concepts: A framework for research[END_REF][START_REF] Devichi | About the concept of angle in elementary school: Misconceptions and teaching sequences[END_REF]. Many students for instance consider that an angle's size depends on the length of its arms; or that one arm must be horizontal and the direction always counterclockwise; or that the angle is a sector in a circle (i.e. a "slice of pizza"). [START_REF] Tanguay | The semiotic and conceptual genesis of angle[END_REF] hypothesize that this misconception is a possible effect of the systematic use of the protractor, when measures in degrees are at stake. Moreover, the confusion between the mathematical concept and the shape that represents it generate mistakes when students consider the spatial characteristics of the design representing the angle [START_REF] Balacheff | Une étude des processus de preuve en mathématiques chez les élèves de Collège[END_REF].

Students face some difficulties in using a protractor, which have been stressed in the literature. For example, [START_REF] Close | Children's understanding of angle at primary/secondary transfer age[END_REF] observed mistakes due to a lack of mental representation of the protractor's angle to superimpose to the angle to be measured or due to the complexity of the dual scale. [START_REF] Tanguay | La notion d'angle au début du secondaire[END_REF] summarizes some well-known difficulties encountered by students: they align the edge of the protractor body itself along one of the angle's arm instead of the baseline; or they don't place the protractor origin over the vertex of the angle to be measured. They can also read the measure on the wrong scale or on the right scale but in the wrong direction, for example by reading on counterclockwise graduation 39° left to 40° instead of 41°.

About actions with instruments

We consider four categories of knowledge according to a theoretical framework to study actions with instruments [START_REF] Petitfour | Enseignement de la géométrie à des élèves en difficulté d'apprentissage : étude du processus d'accès à la géométrie d'élèves dyspraxiques visio-spatiaux lors de la transition CM2-6 ème[END_REF] 1 :

-geometric knowledge about geometric objects, relations and properties -graphic knowledge about representation of geometric objects (symbolic signs, drawings) -technical knowledge about the instrument functionality, its use to obtain the graph and the theoretical relationship between the graphical trace and parts of the instrument -practical knowledge about a given artifact, connected to its concrete handling and to a concrete organization of the action with it

Methodology

We study the practice of one teacher, Marie, who wanted to experiment with a new style of instruction: the flipped classroom. Thus, her students should learn some mathematical content online, by watching video lectures at home before the class session, whereas in the classroom, they should solve more exercises. Consequently, the teacher would be freer in the class session for discussing with the students: that should lead her to a more personalized guidance and to greater interactions with students than traditional teaching.

In our study, three components are common to the two situations that we analyze here: institutional, personal and social. Marie's components can be defined as follows: she is appreciated by her supervisors, colleagues and students. She thinks that in order to learn (and to teach) well it is necessary to handle and to solve a lot of exercises. She finds that she has never enough time. She is concerned about the learning of her students. She teaches in a rural school without social difficulties. In her two 5 th -grade classes, she volunteers to include gifted students. These three components are stable and the same in the two situations. Thus, we can compare the practice of the same teacher in two 5 th -grade classes in the same area. Consequently, we can focus only on the mediative and cognitive components. In order to foster the comparison, we asked Marie to teach the same content and to propose the same tasks in her two different classes, one with video lectures and the other one without.

Data

In order to describe practices and inform mediative and cognitive components involved in the Double Approach, we focused on:

-one video for the 'flipped classroom' and two for the ordinary class that we have transcribed -two short video lectures which we have transcribed -the notebook lessons, exercises book and topics of assessment the teacher's interviews conducted before and after the sessions We have split each session in episodes. We have identified different types of episodes in relation with the teacher's specific goals and exposure of knowledge [START_REF] Allard | Analysis of teachers' practices: The case of fraction teaching at the end of primary school in France[END_REF]. For example, in the lecturing session, the teacher remembers specific words (how to call angles according to their openings measured in degrees) at the beginning of the class session. The teacher also recalls to the students the specific symbol to note an angle (𝐴𝐵𝐶 ̂). These moments are reminder episodes (type 1): the teacher recalls of previous knowledge. Regulation episodes (type 4) are moments when the teacher intervenes to explain and to anticipate difficulties. The main goal of the regulation episodes is to provide students' progress. So we have identified six types of episodes.

For lecturing sessions

The two lecturing sessions last 45 minutes. The aim of the first session is to measure an angle with the protractor. The aim of the second session is to draw an angle of a given measurement. They follow the same organization in six types of episodes (table 1). The teacher talks to the entire class during certain types of episodes: 1, 2, 3, 4 and 6. Students are then facing the blackboard. It is only during the episode of type 5, that students work individually to solve exercises and the teacher interacts with them about their errors or difficulties.

For the classroom with tablet Some students did not have access to the learning platform at home (because of one technical problem), as a result they did not watch the video session before the session in the classroom. Therefore, the teacher improvised and gave time during classroom session to watch and to listen to the video-class on the touch screen tablet. So, it's an opportunity for us to observe students discovering by themselves a mathematic lesson. This session lasts 45 minutes. We have then identified three types of episodes (table 2).

3 Presentation of the new knowledge by the video sessions about measuring and drawing angles with a protractor 4 Regulation episode: reviewing any personal concerns or difficulties that are raised during the session 5

Exercises episode: providing activities and handing out methodological and exercises sheet

Table 2: the three types of episodes for video session

Students worked in groups (by pairs) and watched the video lessons (episode of type 3). After that, they completed some exercises (the same ones that in the ordinary session class). The teacher walked around and talked with students to regulate their work one by one. For example, once more she explained how to handle the protractor.

Data analysis

Comparison of the episodes

Ordinary class requires two sessions instead of only one for the class with the touch screen tablet in order to learn the same content. For the teacher, it seems to be an efficient method. But our study shows that less knowledge is going around in the class in the case of touch screen classroom (episodes of type 1, 2, 6 are absent), there is no link between previous knowledge and the new one, no collective reminder by the teacher and a lack of formulation of the knowledge by the students.

In the ordinary classroom, students listen to each other and listen to the teacher, they raise their hand in order to come to the blackboard, they do individual exercises and sometimes ask questions or answer question the teacher's ones. They are facing the blackboard, which promotes discussions between themselves and the teacher. In the touch screen tablet session, students watch the first video session several times and they solve the exercises individually. While they work on the exercises, many students listen to the touch screen tablet: they look at the gestures in the screen and they try to do the same, they stop, observe and copy. After that, they watch the second video and do exercises. Meanwhile, the teacher walks around the pair groups, corrects mistakes, rectifies the bad handling of the protractor.

In the ordinary classroom, the teacher leads her students to use an appropriate language during the presentation of the new knowledge episode: for example, "center" for the center of the protractor instead of "hole". We can see that the students appropriated this formulation in the ordinary classroom whereas they did not in the other classroom even if they had listened to the session video several times. We can see in this comparison to what extent the working methods seems to change what is said and what is shared.

Now we compare what changes at the level of the potential learning about angle and the use of the protractor.

Knowledge at stake

Actions with a protractor in order to measure an angle or to draw an angle with a given measurement involve different pieces of knowledge. We study the knowledge at stake in the types of episodes where this knowledge is exposed to all the students, that is to say where the whole class has the opportunity to hear or to see the same thing. It concerns episodes of types 1, 2, 3, 4, 6 in the sessions without a tablet and type 3 in the session with a tablet.

Some geometric knowledge appears explicitly in the session without a tablet whereas it does not in the session with a tablet. On the one hand, the classification of angles based on the degree measurement is recalled: angles are categorized according to their openings measured in degrees: an angle can be right, acute, obtuse, straight, zero or reflex. On the other hand, "angle" is defined as formed by two rays (sides) that have the same endpoint (vertex), and "ray" is defined as a line extending indefinitely in one direction from a point. In the same way, graphic knowledge appears explicitly only in the session without a tablet: first, the symbol Λ enables to distinguish an angle and a triangle; second, an angle can be named with three letters, the second letter names the vertex, the first names a point on one side and the third a point on the other side. The fact that the line representing the ray can be extended in one side is mentioned in both sessions but only explained referring to some geometric knowledge in the session without a tablet.

As far as the representations of an angle are concerned, drawings are more numerous in the session without a tablet. Indeed, in this latter session, five angles are drawn on the whiteboard, one is freehand traced and the others are traced with one of the edges of a set square. Besides, one is obtuse and four are acute with similar opening around 45° but which one with the vertex at right (it allows to use both protractor's scales) (Figure 1). At last, the five drawings have a horizontal side and are named with three points. The drawing of the angle 𝐹𝑂𝐺 ̂, 52° had been presented by two students on the blackboard and each time, they have drawn an arc of a circle along the semi-circular edge of the protractor despite the fact that the teacher mentioned the uselessness of this curved line. This representation has led some other students to speak explicitly about "cake slice" which revels the misconception of the angle as a sector in a circle.

Only two acute angles are drawn on a paper in the session with tablet. They are oriented in a nonprototypical way and are named with the letter of the vertex (upper case) and the letters of the direction of each ray (lower case) (Figure 2). It is not this latter notation that is used in the application exercise but the notation with three points. In both sessions, drawn angles are named both spoken and written. In the session without a tablet, the teacher sometimes used gestures too (Figure 3) expressing either the "ray" aspect or the "region" aspect of an angle. Moreover, in the case of the obtuse angle 𝐴𝑂𝐶 ̂ (Figure 1), she used a symbolic signa small arc of a circlein order to indicate what angle is to be considered. In the session with a tablet, there are only deictic gestures pointing the letters "x", "O" and "y" when they are uttered in order to name the measured angle.

Some technical knowledge is recalled only in the session without a tablet. This knowledge concerns the protractor's functionality: a protractor is a measuring instrument, the measurement is expressed in degrees; and a description of the protractor parts to link with the graphical representation of an angle. Indeed, the localisation of the protractor's centre is first given in a general way, by the use of language accompanied by gestures, then the graduation 0° and the dual scale (inner and outer) from 0° to 180° are named and pointed on the protractor by the teacher.

The steps to measure an angle and the steps to draw an angle using a protractor are formulated in the same way in the two sessions. What is said is exactly what is written on the summary sheet given to the students. For example, here are stated the three steps to measure an angle: first, place the protractor so that the centre is over the vertex of the angle to be measured; second, place the graduation zero degree over one side of the angle; third, follow the graduations of zero degree, ten degrees, twenty degrees, … until you reach the other side of the angle. It is also stated that perceptive evaluation of the opening of the anglegreater or smaller than the one of the right angleenables to control possible measurement errors.

In the session with a tablet, the students can hear and see the operating filmed sequence as many times as they wish, pause and go back whereas in the session without a tablet, the operating sequence is presented several times by different students on the blackboard (for example, three times to measure an angle before doing the application exercise). The teacher helps the students to formulate the method they implemented.

Practical knowledge appears only in the session without a tablet. For example, some protractors have a hole to show the centre near the bottom of the protractor whereas the blackboard's protractor has his centre on the bottom; the semi-circular edge of the protractor can be damaged so that it is better to avoid tracing along this edge; if the protractor goes beyond the lines represented sides of an angle to be measured, then the lines must be extended. Regarding organizational aspects, the teacher gave students the advice to store the protractor in a pocket in their workbook to avoid breaking it.

Results and conclusion

Our analysis of one teacher's practice about the use of the protractor allowed us to point out the following results. Some of the students 'difficulties and mistakes are the same in both sessions, with and without tablet, when the students trace or measurement by themselves during the exercises episodes: wrong localization of the measure on the protractor, measurement without extending the line representing ray when it is necessary, clumsy handling of the protractor. Errors to note and to name points and rays appeared only in the session with tablet (students didn't manage to adapt what was presented in the video lecture). Moreover, there are inaccurate wordings that show confusion between length and angle. The correction of the arising errors is private in the both sessions but also public and shared in the session without a tablet. Finally, whatever the case, there is no difference between the assessment results of the two classes, according to the teacher and the collected data cannot inform us about the arrangement that would better foster learning.

This study confirms that the modifications tied to the mediative component, in particular in terms of working arrangements, have a very important impact on the knowledge exposure [START_REF] Allard | Étude du processus institutionnalisation dans les pratiques d'enseignants de fin d'école primaire: Le cas des fractions[END_REF]. Indeed, in the session with tablet, the only exposed knowledge is the knowledge of the tablet, without possible links with difficulties met by the students. In the lecturing session, there is more knowledge exposure thanks to the interactions between the students and their teacher.

Figure 1 :

 1 Figure 1: Drawings of angles in the session without tablet

Figure 2 :

 2 Figure 2: Drawings of angles in the session with tablet

Figure 3 :

 3 Figure 3: Gestures about angles (Left, "ray" aspect and middle and right, "region" aspect)

1

  Reminder episodes:-categorizing angles according to their opening measured in degrees (1 st and 2 nd sessions) -noting and naming the angles (1 st and 2 nd sessions) -defining the center of the protractor, based on a description of the artifact (1 st and 2 nd sessions)

		-measuring angle with a protractor (2 nd session)
		-estimating and controlling the measure (2 nd session)
	2	Methodological episode: estimating and controlling the measure
	3	Presentation of the new knowledge: presenting and discussing the methodological sheet about measuring (first session) and drawing angles (second session) with a protractor.
	4	Regulation episode: -anticipating difficulties (in relation with the dual scale or extend ray)
		-reviewing any personal concerns or difficulties that are raised during the session
	5	Exercises episode: providing activities and handing out methodological and exercises sheets
	6	The correction of the exercises: exposing knowledge and the difficulties encountered

Table 1 : the six types of episodes for ordinary session class

 1

Proceedings of CERME10

This framework is based on an instrumental approach[START_REF] Rabardel | Les hommes et les technologies[END_REF].Thematic Working Group 04Proceedings of CERME10


Fabien Leprieur
email: fabien.leprieur@univ-montp2.fr

Simona Colosio

Patrice Descombes

Valeriano Parravicini

Michel Kulbicki

Peter F Cowman

David R Bellwood

David Mouillot

Loïc Pellissier

-S Colosio

Dm

Historical and contemporary determinants of global phylogenetic structure in tropical reef fish faunas

Identifying the main determinants of tropical marine biodiversity is essential for devising appropriate conservation measures mitigating the ongoing degradation of coral reef habitats. Based on a gridded distribution database and phylogenetic information, we compared the phylogenetic structure of assemblages for three tropical reef fish families (Labridae: wrasses, Pomacentridae: damselfishes and Chaetodontidae: butterflyfishes) using the net relatedness (NRI) and nearest taxon (NTI) indices. We then related these indices to contemporary and historical environmental conditions of coral reefs using spatial regression analyses. Higher levels of phylogenetic clustering were found for fish assemblages in the Indo-Australian Archipelago (IAA), and more particularly when considering the NTI index. The phylogenetic structure of the Pomacentridae, and to a lower extent of the Chaeotodontidae and Labridae, was primarily associated with the location of refugia during the Quaternary period. Phylogenetic clustering in the IAA may partly result from vicariance events associated with coral reef fragmentation during the glacial periods of the Quaternary. Variation in the patterns among fish families further suggest that dispersal abilities may have interacted with past habitat availability in shaping the phylogenetic structure of tropical reef fish assemblages.

those related to evolutionary history and past environmental changes [START_REF] Graham | Habitat history improves prediction of biodiversity in rainforest fauna[END_REF][START_REF] Kissling | Cenozoic imprints on the phylogenetic structure of palm species assemblages worldwide[END_REF]). Among ecological processes, those related to environmental filtering and competition have been widely studied by assessing whether species in a given area are phylogenetically more (clustering) or less (overdispersion) closely related to each other than would be expected by chance or whether these species are a random subset of the regional pool of species [START_REF] Webb | Exploring the phylogenetic structure of ecological communities: an example for rain forest trees[END_REF][START_REF] Webb | Phylogenies and community ecology[END_REF]. The use of phylogenetic relatedness to inform on contemporary ecological processes is based on the assumption that species ecological differences are proportional to the amount of time since they diverged from a common ancestor [START_REF] Webb | Phylogenies and community ecology[END_REF]. As a consequence, closely related species should share similar biological attributes that define the capacity of species to persist within communities in a given environment [START_REF] Graham | Phylogenetic structure of hummingbird communities[END_REF] or under varying competitive pressure [START_REF] Cavender-Bares | Phylogenetic overdispersion in Floridian oak communities[END_REF]). However, phylogenetic relatedness between species may be not a relevant proxy of their biological relatedness if species traits are not phylogenetically conserved (e.g. trait lability resulting from convergent evolution; Losos 2008), Coral reefs support the greatest biodiversity of marine fishes, but this biodiversity is not evenly distributed across oceans with a peak in the Indo-Australian Archipelago (IAA; [START_REF] Bellwood | Environmental and geometric constraints on Indo-Pacific coral reef biodiversity[END_REF][START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF], and the mechanisms underpinning the origin of this pattern are only partially understood [START_REF] Bellwood | Environmental and geometric constraints on Indo-Pacific coral reef biodiversity[END_REF][START_REF] Bowen | The origins of tropical marine biodiversity[END_REF][START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]. Currently, coral reefs are globally affected by climate change [START_REF] Hoegh-Guldberg | Coral reefs under rapid climate change and ocean acidification[END_REF][START_REF] Pandolfi | Projecting coral reef futures under global warming and ocean acidification[END_REF]) and multiple anthropic stressors (e.g. habitat degradation, pollution, overfishing) as they are found in some of the most disturbed coastal zones on Earth [START_REF] Hughes | Climate change, human impacts, and the resilience of coral reefs[END_REF]. Given the present escalation of threats, and the associated biodiversity erosion, a better understanding of the processes that generate and maintain the biodiversity of coral reef fishes is urgently needed.

Species assemblage in a given place and time can be the result of a range of processes, whose relative contribution is debated among ecologists and biogeographers [START_REF] Mittelbach | Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography[END_REF]). These processes can be generally divided into those related to contemporary ecological conditions [START_REF] Götzenberger | Ecological assembly rules in plant communities: approaches, patterns and prospects[END_REF][START_REF] Hughes | Assembly rules of reef corals are flexible along a steep climatic gradient[END_REF]) and which may blur the interpretation of the role of environmental filtering vs competition in shaping assemblage structure [START_REF] Swenson | Phylogenetic resolution and quantifying the phylogenetic diversity and dispersion of communities[END_REF]. In addition, the phylogenetic structure of assemblages may not reflect ongoing ecological processes but rather the legacy of historical and evolutionary processes [START_REF] Cardillo | Phylogenetic structure of mammal assemblages at large geographical scales: linking phylogenetic community ecology with macroecology[END_REF][START_REF] Kissling | Cenozoic imprints on the phylogenetic structure of palm species assemblages worldwide[END_REF][START_REF] Cantalapiedra | The biogeographic history of ruminant faunas determines the phylogenetic structure of their assemblages at different scales[END_REF].

The role of historical and evolutionary processes in shaping the phylogenetic structure of assemblages is recognized both in regards to phylogenetic clustering and overdispersion of assemblages [START_REF] Wiens | Historical biogeography, ecology and species richness[END_REF]. In situ diversification within isolated regions such as biogeographic regions may result in an assemblage where species are more closely related than in the global pool of species [START_REF] Kissling | Cenozoic imprints on the phylogenetic structure of palm species assemblages worldwide[END_REF]). In the case of palms [START_REF] Kissling | Cenozoic imprints on the phylogenetic structure of palm species assemblages worldwide[END_REF] or large ruminant mammals [START_REF] Cantalapiedra | The biogeographic history of ruminant faunas determines the phylogenetic structure of their assemblages at different scales[END_REF], long term geographic isolation has shaped patterns of phylogenetic clustering worldwide, where on distinct continents closely related species have colonized contrasted sub-regions or biomes [START_REF] Cardillo | Phylogenetic structure of mammal assemblages at large geographical scales: linking phylogenetic community ecology with macroecology[END_REF]. Historical formations of geographic barriers such as mountain ranges have also shaped contrasted phylogenetic structure of species assemblages [START_REF] Graham | Phylogenetic structure of hummingbird communities[END_REF]. It has been further suggested that the frequency and magnitude of earth processes during the Tertiary and Quaternary periods, such as climatic fluctuations or continental drift, have likely been decisive in shaping the present-day phylogenetic structure of species assemblages [START_REF] Hortal | Ice age climate, evolutionary constraints and diversity patterns of European dung beetles[END_REF]).

In the marine realm, historical and evolutionary processes can also explain contemporary patterns of species assemblage structure. For instance, the fractioning of populations into differentiated lineages as a result of the geological complexity of the region (Renema et al. 2008, Cowman andBellwood 2013a) and eustatic sea level changes (McManus 1985, Ludt and[START_REF] Ludt | Shifting seas: the impacts of Pleistocene sea-level fluctuation on the evolution of tropical marine taxa[END_REF] may have shaped the biodiversity of coral reefs. For instance, Quaternary climate fluctuations of available coral reef habitat for reef fishes largely explain richness patterns worldwide [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]. During cycles of global cooling, and following temperature and sea level shifts, coral reef habitats were only maintained in some refugia, where environmental conditions remained favourable for their development [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF], but isolated from each other by barriers potentially promoting allopatric or parapatric speciation [START_REF] Mcmanus | Marine speciation, tectonics, and sea level changes in south-east Asia[END_REF][START_REF] Potts | Sea-level fluctuations and speciation in Scleratinia[END_REF]. The Indo-Pacific region, and more particularly the IAA, maintained extensive coral reef refugia during cold periods while the Atlantic had only very limited areas suitable for coral reefs, implying a further degradation of Caribbean coral reefs after the onset of glaciations following the Panama closure [START_REF] O'dea | Environmental change preceded Caribbean extinction by 2 million years[END_REF]). These disparate environmental histories are strongly reflected in the evolution of reef fishes among the major coral reef realms (Cowman and Bellwood 2013a). Historical processes during the Quaternary promoting the rise and fall of species are therefore expected to have played a major role in shaping global patterns of phylogenetic structure in tropical reef associated species.

Here, we mapped the phylogenetic structure of tropical reef fish assemblages globally using a grid-based database on tropical reef fish distribution [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]) and the phylogenies of three reef fish families, namely Pomacentridae, Chaetodontidae and Labridae [START_REF] Cowman | Coral reefs as drivers of cladogenesis: expanding coral reefs, cryptic extinction events, and the development of biodiversity hotspots[END_REF]. We focused on these families because 1) they are among the most widespread, diverse and abundant on coral reefs globally [START_REF] Bellwood | The history and biogeography of fishes on coral reefs[END_REF], 2) the current phylogenetic resolution within each family comes from over a decades worth of sequencing and phylogenetic effort across the ichthyological community (Pomacentridae: [START_REF] Tang | Phylogenetic relationships among damselfishes[END_REF][START_REF] Jang-Liaw | Molecular phylogeny of 48 species of damselfishes (Perciformes: Pomacentridae) using 12S mtDNA sequences[END_REF][START_REF] Quenouille | Molecular systematics of the damselfishes (Teleostei: Pomacentridae): Bayesian phylogenetic analyses of mitochondrial and nuclear DNA sequences[END_REF][START_REF] Cooper | Exploring the radiation of a diverse reef fish family: phylogenetics of the damselfishes (Pomacentridae), with new classifications based on molecular analyses of all genera[END_REF], Chaetodontidae: McMillan and Palumbi 1995[START_REF] Fessler | Molecular phylogenetics of the butterflyfishes (Chaetodontidae): taxonomy and biogeography of a global coral reef fish family[END_REF][START_REF] Bellwood | Evolutionary history of the butterflyfishes (f: Chaetodontidae) and the rise of coral feeding fishes[END_REF], Labridae: Barber and Bellwood 2005[START_REF] Read | Ancient origins of Indo-Pacific coral reef fish biodiversity: a case study of the leopard wrasses (Labridae: Macropharyngodon)[END_REF][START_REF] Smith | Phylogenetic relationships and the evolution of regulatory gene sequences in the parrotfishes[END_REF][START_REF] Kazancioglu | Influence of sexual selection and feeding functional morphology on diversification rate of parrotfishes (Scaridae)[END_REF], and 3) they display highly contrasted dispersal and colonization abilities [START_REF] Luiz | Adult and larval traits as determinants of geographic range size among tropical reef fishes[END_REF]. Pomacentridae have low sustained swimming ability of late pelagic stage, are demersal spawners [START_REF] Luiz | Adult and larval traits as determinants of geographic range size among tropical reef fishes[END_REF]) and frequently show high biotic dependency to coral reef habitat [START_REF] Litsios | Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae)[END_REF]. Clades with low dispersal abilities seem to be more subject to allopatric speciation promoting diversification [START_REF] Sandel | Climate change and the invasion of California by grasses[END_REF] and comparing phylogenetic structure across clades allows better documentation of the mechanisms underpinning species formation and assembly. We then investigated whether contemporary or historical environmental conditions best explain spatial variation in the phylogenetic structure of tropical reef fish assemblages. For instance, if allopatric or parapatric speciation across multiple refugia during periods of isolation, is the major factor shaping phylogenetic structure of tropical reef fish assemblages, phylogenetic clustering should be more important in proximity to stable (but fragmented) coral reef refugia concentrated in the IAA [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]. In contrast, if contemporary ecological processes such as environmental filtering shape phylogenetic structure of assemblages, we can expect increasing phylogenetic clustering along environmental gradients, and more particularly towards cold temperatures at higher latitudes [START_REF] Qian | Phylogenetic community ecology: integrating community ecology and evolutionary biology[END_REF]. Contemporary environmental filtering based on climatic tolerances conserved across lineages (i.e. phylogenetic niche conservatism) would be therefore the main force structuring assemblages.

Methods

Global distribution of tropical reef fishes

We obtained information on presence/absence of reef fish at 169 locations worldwide examining almost 500 references and extracting information from published works, regional checklists, monographs on specific families or genera, and reports [START_REF] Parravicini | Global patterns and predictors of tropical reef fish species richness[END_REF]. To increase the homogeneity of information among species lists, we focused our analysis on shallow water species (between 0 and 75 m depth). Overall, we obtained information on the distribution of 6316 reef fishes. As lists of each of the 169 locations are unlikely to have complete lists of the species that occur there, we constructed an extent of occurrence map for each species, defined as the convex hull polygon of the locations where each species was present. Species composition was then extracted from grid cells of 5 5 , corresponding to approximately 555 555 km at the equator. The grain size of the grid of 5 5 was chosen because it represents a good compromise between the desired resolution and the geographical density of information. We excluded from our analyses all cells not containing coral reef for shallow water species. Bathymetric data were obtained from the SRTM30_PLUS bathymetry (Shuttle Radar Topography Mission, available at: http:// topex.ucsd.edu/WWW_html/srtm30_plus.html ) while information on the distribution of coral reefs was obtained from available information partially based on the Millenium Coral Reef Mapping project and downloadable at: http:// data.unep-wcmc.org . We also removed cells with more than 90% of the surface inland. We additionally excluded those cells corresponding to areas were we had an original gap of information. These include the cells corresponding to the Gulf of Mexico, the estuary of the Amazon River and few cells in the NW part of Australia. From this database, we extracted the occurrences of nearly all known species for the Labridae (n 567), Chaetodontidae (n 127) and Pomacentridae (n 371) families.

Fish phylogenies

We used the dated phylogenies of the three families published in [START_REF] Cowman | Coral reefs as drivers of cladogenesis: expanding coral reefs, cryptic extinction events, and the development of biodiversity hotspots[END_REF] comprising 278 species out of the 567 reef Labrid species, 96 out of 127 species for the Chaetodontidae family, and 176 out of 371 species for the Pomacentridae family. These phylogenies and related information (i.e. information on taxa sampled in each family, accession number for GenBank sequences, and primary publication source) are available at http:// datadryad.org/resource/doi:10.5061/dryad.m8s502qb . We incorporated other species by grafting new tips onto the backbone phylogenies based on published phylogenies for these families at lower taxonomic scale, supplemented by taxonomic information from fish identification guides (Supplementary material Appendix 1) and FishBase ( www. fishbase.org ). Where information allowed, new tips representing unsampled species were added to direct sister species or to the base of the clade representing its genus. Tips were added using the bind.tip() function implemented in the R package 'phytools' [START_REF] Revell | Phytools: an R package for phylogenetic comparative biology (and other things)[END_REF]. The resulting polytomies were subsequently randomly resolved using a birthdeath model following the procedure proposed by [START_REF] Kuhn | A simple polytomy resolver for dated phylogenies[END_REF] in R (R Development Core Team) and BEAST [START_REF] Drummond | Bayesian phylogenetics with BEAUti and the BEAST 1.7[END_REF]. More specifically, 11 111 000 permutations were runs and the trees were sampled at every 1000th permutation. At each permutation, the first 10% trees were discarded as burn-in, hence yielding a posterior distribution of 10 000 trees from which we randomly sampled 1000 trees for use in a sensitivity analysis (see below).

Phylogenetic assemblage structure metrics

For each grid cell and for each family, we characterized the phylogenetic structure of fish assemblages using two metrics: the net relatedness index (NRI) and the nearest taxon index (NTI) as standardized values of the mean pairwise distance (MPD) and the mean nearest taxon distance (MNTD), respectively [START_REF] Webb | Exploring the phylogenetic structure of ecological communities: an example for rain forest trees[END_REF][START_REF] Webb | Phylogenies and community ecology[END_REF]. MPD represents the mean pairwise phylogenetic distance between all species in each assemblage, while MNTD represents the mean phylogenetic distance separating each species in the assemblage from its closest relative. NRI and NTI were computed as standardized effect sizes, i.e. by comparing the MPD and MNTD values in the observed assemblages to those generated by shuffling 999 times the names of taxa across the tips of the phylogeny. This frequently used null model [START_REF] Kissling | Cenozoic imprints on the phylogenetic structure of palm species assemblages worldwide[END_REF][START_REF] Cantalapiedra | The biogeographic history of ruminant faunas determines the phylogenetic structure of their assemblages at different scales[END_REF]) allows randomizing the relatedness of species to one another, while maintaining species occurrence frequency and species richness. Positive NRI and NTI values indicate that assemblages are phylogenetically clustered, i.e. that species are more closely related than expected, while negative values indicate phylogenetic overdispersion, i.e. that species are more distantly related than expected. The use of the two metrics is complementary as NRI is more sensitive to phylogenetic tree-wide patterns while NTI to patterns towards the tips of the tree [START_REF] Webb | Exploring the phylogenetic structure of ecological communities: an example for rain forest trees[END_REF][START_REF] Webb | Phylogenies and community ecology[END_REF]. NTI is indeed calculated from the tips of the phylogeny and hence reflects the terminal phylogenetic structure of assemblages while NRI reflects the basal phylogenetic structure of assemblages [START_REF] Webb | Exploring the phylogenetic structure of ecological communities: an example for rain forest trees[END_REF][START_REF] Webb | Phylogenies and community ecology[END_REF]. In the context of hypothesis testing, NTI is therefore more relevant than NRI for evaluating the influence of recent historical events (e.g. during the Quaternary period).

Both NRI and NTI are potentially sensitive to the definition of the species pool [START_REF] Cardillo | Phylogenetic structure of mammal assemblages at large geographical scales: linking phylogenetic community ecology with macroecology[END_REF][START_REF] Cantalapiedra | The biogeographic history of ruminant faunas determines the phylogenetic structure of their assemblages at different scales[END_REF]). For instance, recent studies emphasized the need to explicitly define biogeographical species pools to tease apart the relative roles of historical vs. ecological factors in shaping assemblage structure [START_REF] Cantalapiedra | The biogeographic history of ruminant faunas determines the phylogenetic structure of their assemblages at different scales[END_REF]). In the present study, we first considered the global pool of tropical reef fishes and then the species pool of Indo-Pacific region only, hence excluding the Atlantic and Tropical Eastern Pacific faunas. Indeed, the tropical reef fish fauna of the Indo-Pacific region (including the IAA hotspot) display a different biogeographical history compared to the Atlantic and Tropical Eastern Pacific regions (Cowman and Bellwood 2013a, b).

In the above analyses, we used a phylogenetic tree with a number of polytomies. We therefore performed a sensitivity analysis to assess whether this uncertainty in branch length estimation affected our results and hence our conclusions [START_REF] Swenson | Phylogenetic resolution and quantifying the phylogenetic diversity and dispersion of communities[END_REF]. To do so, we calculated the Pearson's correlation coefficient between the MPD (and MNTD) values based on the phylogenetic tree with polytomies and the MPD (and MNTD) values based on 1000 trees taken at random from the Bayesian posterior distribution of the 10 000 fully resolved phylogenetic trees. The sensitivity analysis showed that the MPD and MNTD metrics calculated from the unresolved phylogenetic trees were unbiased estimates. For each family, we found strong correlations (r 0.9) between the MPD (and MNTD) values based on the unresolved tree and the MPD (and MNTD) values based on 1000 randomly resolved trees (Supplementary material Appendix 2, Table A1). We therefore calculated the NRI and NTI indices with the unresolved phylogenetic trees to avoid running the null models with hundreds of randomly resolved trees.

Contemporary and past environmental conditions

To explain the phylogenetic structure of reef fish assemblages, we used several variables related to contemporary importance of each predictor variable in explaining NRI (and NTI) was assessed by summing Akaike weight values (W AIC ) of each subset model including the predictor [START_REF] Burnham | Model selection and multimodel inference: a practical information-theoretic approach[END_REF]. These summed Akaike weights range from 0 to 1 and provide a ranking of predictor variables in terms of information content (Sandel and Dangremond 2011). Finally, we selected the minimum adequate model (MAM) based on the lowest AIC.

To run the univariate and multivariate SAR models, we used a spatial weight matrix with neighbourhoods defined as all cells within 800 km of the focal cell (i.e. from its centroid), and applied a Moran's I global test to determine whether residual autocorrelation persisted in the SAR models. We used a range of distances (i.e. 800, 1000, 1500 and 2000 km) to define the neighbourhood of each grid cell and preliminary analyses showed that only a distance of 800 km allowed removing spatial autocorrelation in model residuals. The above statistical analyses were performed using the package 'MASS', 'spdep' and 'MuMIn' in R (R Development Core Team, www.R-project.org ).

Results

We found contrasted spatial patterns of phylogenetic assemblage structure among families (Table 1 and Fig. 1) with Labridae showing higher values of NRI (Student's t-test: p 0.0001; Supplementary material Appendix 2, Table A2) and NTI (Student's t-test: p 0.0001; Supplementary Appendix 2, Table A2) compared to Pomacentridae and Chaetodontidae. In addition, Pomacentridae displayed higher values of NRI (Student's t-test: p 0.0001, Supplementary Appendix 2, Table A2) and NTI (Student's t-test: p 0.039; Supplementary material Appendix 2, Table A2) than Chaetodontidae. For each family, the observed patterns of phylogenetic assemblage structure and the relationships between NRI and NTI and the contemporary and historical variables are detailed below.

Pomacentridae

The phylogenetic structure of the Pomacentridae showed high clustering values around the IAA when considering both NRI and NTI (Fig. 1). A similar result was found when only considering the species pool of the Indo-Pacific region (Fig. 2). In other regions, in the East Pacific and Atlantic, environmental conditions and Quaternary environmental change. Building on sea surface temperature and sea level paleo-conditions from sediment cores, we mapped the paleo-distribution of coral reef habitat limited by depth and temperature at a 5 5 resolution, for the last three million years with a temporal resolution of 1000 yr (see [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF] for more details). In particular, we computed two variables both potentially affecting the phylogenetic structure of fish assemblages: 1) the coral reef area per cell of 5 5 during the 10th percentile of coldest periods and 2) the isolation from coral reef refugia across the Quaternary (see [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF] for further details). Current coral reef area has been shown to be a major driver of coral reef fish diversity [START_REF] Parravicini | Global patterns and predictors of tropical reef fish species richness[END_REF], as the greater the habitat area, the higher the number of species that can be maintained. We therefore estimated the total coral reef area (km 2 ) for each grid cell based on data obtained from the Millenium Coral Reef Mapping project. In order to account also for the potential effect of current biogeographical isolation of coral reefs, a measure of isolation was calculated based on the distance to the nearest coral reef habitat patches [START_REF] Parravicini | Global patterns and predictors of tropical reef fish species richness[END_REF]. The influence of current climatic conditions was also considered using the current yearly average sea surface temperature for each cell. This information was obtained in the form of raster files from the Bio-ORACLE database at a resolution of 5-arcmin [START_REF] Tyberghein | Bio-ORACLE: a global environmental dataset for marine species distribution modelling[END_REF]) available at www.oracle.ugent.be . These estimates are based on monthly mean values (from 2002 to 2009).

Statistical analyses

We first assessed the relationship between NRI (and NTI) and each of the considered historical (past coral reef area and isolation from Quaternary refugia) and contemporary (current mean sea surface temperature, current coral reef area and current isolation) variables using a bivariate ordinary least squares (OLS) model. We used the coefficient of determination (R 2 ) to quantify the proportion of variation in NRI (and NTI) explained by the bivariate linear regression models. To account for potential non-linear associations between NRI (and NTI) and the predictor variables, we tested the quadratic term of each predictor variable. Current coral reef area variable was log-transformed prior analyses. Linear regression models may leave a variable degree of spatial autocorrelation in the residuals, which may bias parameter estimates and affect their statistical significance [START_REF] Kissling | Spatial autocorrelation and the selection of simultaneous autoregressive models[END_REF]. We therefore compared the parameter estimates based on a linear regression model to those obtained using a simultaneous autoregressive (SAR) model [START_REF] Kissling | Spatial autocorrelation and the selection of simultaneous autoregressive models[END_REF]. A SAR model adjusts for spatial autocorrelation by incorporating a spatially dependent error term.

We then run OLS and SAR models including both contemporary and historical variables. Specifically, we quantified the support for each competing models including all possible combination of contemporary and historical variables by using the Akaike information criterion (AIC; [START_REF] Burnham | Model selection and multimodel inference: a practical information-theoretic approach[END_REF]. The probability that a specific model is the best was estimated with the Akaike weight (w) for each subset model [START_REF] Kissling | Spatial autocorrelation and the selection of simultaneous autoregressive models[END_REF]. Then, the relative

Discussion

Our results revealed high levels of phylogenetic clustering of fish assemblages across the IAA, a pattern also observed for Scleractinian corals by [START_REF] Huang | The future of evolutionary diversity in reef corals[END_REF]. Phylogenetic structure at the scale considered in the current study is expected to arise from historical processes [START_REF] Kissling | Cenozoic imprints on the phylogenetic structure of palm species assemblages worldwide[END_REF], but be maintained by the structure of contemporary environment. We found a strong relationship between the phylogenetic structure of fish assemblages and the isolation from refugia during the Quaternary, suggesting that the glacial era played a major role in shaping phylogenetic assemblage structure, especially in the IAA. However, we cannot exclude that phylogenetic clustering may also result from sister species during the Quaternary glaciations [START_REF] Mcmanus | Marine speciation, tectonics, and sea level changes in south-east Asia[END_REF][START_REF] Bellwood | The history and biogeography of fishes on coral reefs[END_REF], Cowman and Bellwood 2013a[START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]). However, complementary studies in the field of historical biogeography are clearly needed to assess the relative importance of old vs. recent historical events in explaining the high level of phylogenetic clustering observed in the IAA. We compared the phylogenetic structure of fish assemblages among three reef fish families. The likelihood of lineage divergence following allopatric or parapatric speciation should be higher for taxa with limited dispersal capacity sufficient to isolate populations as they are more strongly affected by habitat fragmentation [START_REF] D'aloia | Seascape continuity plays an important role in determining patterns of spatial genetic structure in a coral reef fish[END_REF]. In support, [START_REF] Riginos | Dispersal capacity predicts both population genetic structure and species richness in reef fishes[END_REF] showed that reef fish speciation rates were associated with fish dispersal abilities. In our analyses, we observed a larger effect of isolation from Quaternary refugia on the phylogenetic structure for the Pomacentridae family compared to Chaetodontidae and Labridae. Pomacentridae have generally low sustained swimming ability of late pelagic stage compared to other fish families and are demersal spawners while the two other families are broadcast. As pelagic eggs cannot actively disperse, larvae retention is expected to be highest for demersal spawners thus reducing their dispersal abilities [START_REF] Luiz | Ecological traits influencing range expansion across large oceanic dispersal barriers: insights from tropical Atlantic reef fishes[END_REF]). In addition, Pomacentridae frequently established specialized biotic interaction with species within coral reefs such as anemone, corals or urchins, which limit their colonization abilities of reef where mutualistic organisms are not present [START_REF] Litsios | Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae)[END_REF]. In contrast, Labridae have many older lineages [START_REF] Cowman | Coral reefs as drivers of cladogenesis: expanding coral reefs, cryptic extinction events, and the development of biodiversity hotspots[END_REF]) with a diverse array of generalist and specialist feeding modes [START_REF] Cowman | Dating the evolutionary origins of wrasse lineages (Labridae) and the rise of trophic novelty on coral reefs[END_REF]). Most of their lineage diversification happened in the Miocene and is linked to the expansion of coral reef habitats during that period. With their high dispersal potential, many labrid lineages would have been able to reach farther refugia before the Quaternary and remained there until dispersal corridors opened up again, which would then have been followed by some vicariance among regions (Cowman and Bellwood 2013b). The influx of those new colonists from other refugia may therefore explain the less marked pattern of phylogenetic clustering for this family. The higher values of NRI and NTI for the Labridae around Thailand and Malaysia as opposed to the central IAA likely reflect a stronger connection between the Central Pacific Islands and the eastern IAA, than the West Indian and western IAA. Overall, differential responses among families therefore suggest that species diversification in the face of historical habitat fragmentation may be shaped by their dispersal abilities.

Our results also revealed contrasted spatial patterns of NRI and NTI for the Chaetodontidae family. High levels of phylogenetic clustering were indeed observed in the IAA when using the NTI metric, which implies that the closest related species are closer than expected by random expectations in this region. In contrast, the use of the NRI metric indicated that species assemblages were weakly overdispersed in the IAA (Fig. 1). It is also worth noting that the NRI metric for the Chaetodontidae shows broadly both low positive and negative values (Fig. 1 and Table 1), hence indicating that the mean phylogenetic distance between species in a given assemblage did not strongly differ from that expected by chance. Such homogeneity in the basal phylogenetic tectonic rearrangements during the Miocene, which generated the complex configuration of the archipelago in this area [START_REF] Renema | Hopping hotspots: global shifts in marine biodiversity[END_REF]. Finally, the effect of current isolation of reefs suggests that contemporary processes of dispersal limitation contribute for maintaining the phylogenetic structure of tropical reef fish assemblages.

During cold periods of the Quaternary, coral reefs in the IAA were less extended but also more fragmented than today [START_REF] Voris | Maps of Pleistocene sea levels in southeast Asia: shorelines, river systems and time durations[END_REF][START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF][START_REF] Ludt | Shifting seas: the impacts of Pleistocene sea-level fluctuation on the evolution of tropical marine taxa[END_REF], which may have promoted the formation of species via allopatric or parapatric speciation [START_REF] Mcmanus | Marine speciation, tectonics, and sea level changes in south-east Asia[END_REF][START_REF] Rocha | Speciation in coral reef fishes[END_REF][START_REF] Ludt | Shifting seas: the impacts of Pleistocene sea-level fluctuation on the evolution of tropical marine taxa[END_REF] resulting from geographic isolation between populations [START_REF] Coyne | Speciation[END_REF]). When glacial cycles ended, fish populations probably expanded from the multiple refugia of the IAA into available coral reef habitat 10-times larger and more connected (Bellwood andWainwright 2002, Pellissier et al. 2014). Then, sea level dropped 130 m below current levels during the Pleistocene glacial maxima [START_REF] Voris | Maps of Pleistocene sea levels in southeast Asia: shorelines, river systems and time durations[END_REF], thereby exposing the Sunda and Sahul continental shelves (known also as the Indo-Pacific Barrier) and limiting ocean circulation within the IAA [START_REF] Gaither | Origins of species richness in the Indo-Malay-Philippine biodiversity hotspot: evidence for the centre of overlap hypothesis[END_REF]. This barrier led to allopatric differentiation of populations spanning both the Indian and Pacific Oceans. Following sea-level rise, the geographical ranges of formerly separated sister taxa expanded and hence overlapped in the IAA [START_REF] Gaither | Origins of species richness in the Indo-Malay-Philippine biodiversity hotspot: evidence for the centre of overlap hypothesis[END_REF]. Neutral genetic differentiation during the Pleistocene sea-level fluctuations has been documented for many coral reef taxa across a range of speciation stages (i.e. supra-or infra-species) providing further evidence for this mechanism [START_REF] Bay | High genetic diversities and complex genetic structure in an Indo-Pacific tropical reef fish (Chlorurus sordidus): evidence of an unstable evolutionary past?[END_REF][START_REF] Fitzpatrick | The West Pacific diversity hotspot as a source or sink for new species? Population genetic insights from the Indo-Pacific parrotfish Scarus rubroviolaceus[END_REF][START_REF] Ludt | Living in the past: phylogeography and population histories of Indo-Pacific wrasses (genus Halichoeres) in shallow lagoons versus outer reef slopes[END_REF][START_REF] Tornabene | Support for a 'Center of Origin' in the Coral Triangle: cryptic diversity, recent speciation, and local endemism in a diverse lineage of reef fishes (Gobiidae: Eviota)[END_REF].

Older isolation processes, not explicitly considered in our study, may also partly explain the observed pattern of phylogenetic clustering in the IAA [START_REF] Renema | Hopping hotspots: global shifts in marine biodiversity[END_REF][START_REF] Cowman | Historical factors that have shaped the evolution of tropical reef fishes: a review of phylogenies, biogeography, and remaining questions[END_REF]. For instance, the Indo-Pacific Barrier repeatedly isolated the fish faunas of the Pacific and Indian Oceans as a consequence of eustatic changes in sea level since at least the Pliocene (5.3 mya) [START_REF] Gaither | Origins of species richness in the Indo-Malay-Philippine biodiversity hotspot: evidence for the centre of overlap hypothesis[END_REF]. Also, in the Early Miocene ( 23-16 mya), the Australian plate made contact with the submerged Sundaland and this collision led to closure of the shallow reefs between Sundaland and Australia [START_REF] Lohman | Biogeography of the Indo-Australian Archipelago[END_REF], which increased reef area and the complexity of coral reefs throughout the region. This favoured lineage diversification of coral reef fishes within the IAA at this time (Cowman andBellwood 2011, 2013a). Tectonic rearrangements during the Miocene may have also promoted vicariance events by restricting water flow between the Indian and Pacific oceans (Renema et al. 2008, Gaither and[START_REF] Gaither | Origins of species richness in the Indo-Malay-Philippine biodiversity hotspot: evidence for the centre of overlap hypothesis[END_REF]. This is consistent with recent studies emphasizing that the majority of speciation events predated the Quaternary period for several coral reef fish families [START_REF] Cowman | Historical factors that have shaped the evolution of tropical reef fishes: a review of phylogenies, biogeography, and remaining questions[END_REF][START_REF] Hodge | Temporal evolution of coral reef fishes: global patterns and disparity in isolated locations[END_REF][START_REF] Hodge | On the relationship between species age and geographical range in reef fishes: are widespread species older than they seem?[END_REF]. For instance, the median age of extant species originating in the IAA ranges from 2.45 mya for the Chaetodontidae family to 6.87 and 7.19 mya for the Labridae and Pomacentridae families [START_REF] Cowman | Historical factors that have shaped the evolution of tropical reef fishes: a review of phylogenies, biogeography, and remaining questions[END_REF]; see also Supplementary material Appendix 2, Table A6). Overall, our results suggest that the high level of phylogenetic clustering of fish assemblages across the IAA result from both the emergence of closely related species and the survival of older in the spatial definition of refugia. Future studies should couple several approaches to infer past sea surface temperature including applying temperature anomalies from cores, but also the use of hindcasted climatic models [START_REF] Sbrocco | paleo-MARSPEC: gridded ocean climate layers for the mid-Holocene and Last Glacial Maximum[END_REF].

Together, our results highlight the singular phylogenetic structure of tropical reef fish assemblages in the IAA and suggest that phylogenetic clustering is partly associated with Quaternary glaciations, which have created micro-refugia promoting vicariance and allopatric speciation. These findings parallel recent studies showing that climatic fluctuations during the Quaternary also promoted vicariant events in intertidal or fluvial habitats at higher latitudes [START_REF] Dias | Global imprint of historical connectivity on freshwater fish biodiversity[END_REF][START_REF] Toms | Variation in palaeo-shorelines explains contemporary population genetic patterns of rocky shore species[END_REF]. However, future studies should investigate the role of older processes such as shelves movement following plate tectonic that may also have played a major role in shaping large-scale patterns of tropical marine biodiversity [START_REF] Keith | Faunal breaks and species composition of Indo-Pacific corals: the role of plate tectonics, environment, and habitat distribution[END_REF]. To this aim, the development of stochastic simulation models [START_REF] Gotelli | Patterns and causes of species richness: a general simulation model for macroecology[END_REF]) integrating explicitly the movement of continental shelves through geological time should provide new insights to our understanding of deep time historical processes. structure of species assemblages suggests that dispersal has been important enough to promote the spatial expansion of older lineages of Chaetodontidae throughout tropical oceans (Cowman and Bellwood 2013a). In contrast, the dependence of NTI on terminal branch lengths explains why the terminal phylogenetic structure of species assemblages was found to be more strongly associated to isolation from Quaternary reef refugia, which reflects the high number of divergence events that occurred during the Quaternary period for this family [START_REF] Cowman | Historical factors that have shaped the evolution of tropical reef fishes: a review of phylogenies, biogeography, and remaining questions[END_REF][START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]. Indeed, Chaetodontidae show significantly younger lineages originating in the IAA when compared to Labridae or Pomacentridae [START_REF] Cowman | Historical factors that have shaped the evolution of tropical reef fishes: a review of phylogenies, biogeography, and remaining questions[END_REF]; see also Supplementary material Appendix 2, Table A6). These findings emphasize the importance of using complementary phylogenetic metrics of assemblage structure to highlight the legacy of recent or more ancient historical processes on contemporary species assemblages (see also [START_REF] Gonzalez-Caro | Sensitivity of metrics of phylogenetic structure to scale, source of data and species pool of hummingbird assemblages along elevational gradients[END_REF].

This study supports the important role of historical and evolutionary processes in explaining current patterns of assemblage structure in tropical reef fishes (see also [START_REF] Hubert | Community assembly and diversification in Indo-Pacific coral reef fishes[END_REF] at a finer spatial scale). However, this does not imply that local environmental conditions and ecological interactions do not influence the diversity and distribution of tropical reef fishes. The issue of spatial scale is indeed important to consider when exploring patterns and processes of species diversity and assemblage structure [START_REF] Ricklefs | A comprehensive framework for global patterns in biodiversity[END_REF]Schluter 1993, Cavender-Bares et al. 2009) as the relative importance of historical/evolutionary and ecological processes may vary according to the spatial scale considered [START_REF] Ricklefs | A comprehensive framework for global patterns in biodiversity[END_REF]. In this study, we defined fish assemblages according to a coarse spatial grain (555 555 km) and we did not consider local environmental conditions that characterize coral reef ecosystems. Yet, a number of local-scale studies showed that coral reef habitat characteristics (e.g. coral cover, topographic complexity and coral diversity) strongly influence the structure and composition of coral reef fish species assemblages [START_REF] Komyakova | Relative importance of coral cover, habitat complexity and diversity in determining the structure of reef fish communities[END_REF]. Overall, we recommend future studies to apply a multi-scale approach [START_REF] Brunbjerg | Multi-scale phylogenetic structure in coastal dune plant communities across the globe[END_REF] by combining both local field inventories (i.e. underwater visual transects) and regional checklists or grid cell distributional data. For instance, a valuable research avenue would be to assess the extent to which history left an imprint on local communities of coral reef fishes.

In this study, we also assessed whether contemporary environmental filtering based on climatic tolerances conserved across lineages was a major process shaping the phylogenetic structure of tropical reef fish assemblages. For the three families considered here, species at higher latitudes were not phylogenetically more related to each other (i.e. phylogenetic clustering) than those at lower latitudes. However, this does not imply that climatic niche conservatism is not an important process structuring marine assemblages [START_REF] Jablonski | Out of the tropics, but how? Fossils, bridge species, and thermal ranges in the dynamics of the marine latitudinal diversity gradient[END_REF]). This study is indeed restricted to tropical waters and hence accounts for a lower latitudinal range of temperature. Future works including both temperate and tropical lineages are clearly needed to assess the importance of climate niche conservatism in shaping the phylogenetic structure of fish assemblages in reef systems. Finally, the coverage of the sediment cores was not homogeneous across the tropical seas [START_REF] Pellissier | Quaternary coral reef refugia preserved fish diversity[END_REF]) and this might have led to uncertainty

Figure 1 .

 1 Figure 1. Global distribution of NRI ((A) Labridae, (C) Pomacentridae, (E) Chaetodontidae) and NTI ((B) Labridae, (D) Pomacentridae, (F) Chaetodontidae) values obtained using a null model shuffling the tips of species across the phylogeny. Positive NRI and NTI values indicate phylogenetic clustering while negative values indicate phylogenetic overdispersion. High values of both NRI and NTI were found in the Indo-Australian Archipelago (IAA), also called the coral triangle, which is bounded by the Indonesian archipelago, the Malaysian peninsula, the Philippines, New Guinea and northern Australia.

Figure 2 .

 2 Figure 2. Distribution of NRI ((A) Labridae, (C) Pomacentridae, (E) Chaetodontidae) and NTI ((B) Labridae, (D) Pomacentridae, (F) Chaetodontidae) values obtained using a null model shuffling the tips of species across the phylogeny. The species pool considered here is the Indo-Pacific region (excluding the Tropical Eastern Pacific region and the Atlantic region). Positive NRI and NTI values indicate a phylogenetic clustering while negative values indicate a phylogenetic overdispersion. High values of both NRI and NTI were found in the Indo-Australian Archipelago (IAA), also called the coral triangle, which is bounded by the Indonesian archipelago, the Malaysian peninsula, the Philippines, New Guinea and northern Australia.

Figure 3 .

 3 Figure 3. Relationship between NRI ((A) Labridae, (C) Pomacentridae, (E) Chaetodontidae) and NTI ((B) Labridae, (D) Pomacentridae, (F) Chaetodontidae) and isolation from Quaternary coral reef refugia. Solid black lines represent ordinary least squares (OLS) model fits.

Table 1 .

 1 Summary statistics for the net relatedness (NRI) and nearest taxon (NTI) indices calculated for species assemblages belonging to three reef fish families. The first quartile is the data point at the 25th percentile, and the third quartile is the data point at the 75th percentile.

		Labridae	Pomacentridae	Chaetodontidae
		NRI	NTI	NRI	NTI	NRI	NTI
	Min	-0.968 -0.146 -1.859 -1.648 -1.335 -1.462
	1st quartile 1.557 2.684 -0.725	1.639 -0.548	1.664
	Median	1.927 3.500 -0.106	2.559 -0.145	2.421
	Mean	1.926 3.317	1.015	2.675 -0.034	2.341
	3rd quartile 2.431 3.976	2.884	3.886	0.628	3.367
	Max	4.076 6.354	6.731	6.104	1.601	4.523

Table 2 .

 2 Results of simultaneous autoregressive (SAR) models relating the net relatedness (NRI) and nearest taxon (NTI) indices for three families (Pomacentridae, Chaetodontidae and Labridae) to several contemporary and historical variables. PRAR, past coral reef area; PISO, isolation from refugia during the Quaternary; RAR, current coral reef area (log-transformed); ISO, current isolation among coral reef cells, TEMP, average sea surface temperature. Shown are the standardized coefficients of the minimum adequate model (MAM) with the lowest AIC score and their statistical significance. The relative importance of each predictor variable was assessed using the summed Akaike weights

	(W AIC ). p 0.05, p 0.01,	p 0.001.
					NRI						NTI
			Labridae	Pomacentridae	Chaetodontidae	Labridae	Pomacentridae Chaetodontidae
		MAM	W AIC	MAM	W AIC	MAM	W AIC	MAM	W AIC	MAM	W AIC	MAM	W AIC
	Historical variables
	PRAR	-0.274	0.74	0.057	0.77		0.34		0.40		0.40	0.51
	PRAR 2	0.262	0.64		0.20		0.10		0.16		0.13	0.32
	PISO			0.42 -0.310	0.83		0.62 -0.391	0.74 -0.126	0.98 -0.155	0.91
	PISO 2			0.16	0.171	0.51		0.16	0.329	0.63		0.27	0.25
	Contemporary variables
	RAR			0.33		0.37	0.060	0.63		0.36 0.038	0.62	0.078	0.88
	ISO	-0.117	0.67 -0.123	0.97	-0.289	0.84 -0.231	1	-0.113	0.98	0.56
	ISO 2			0.27		0.25	0.543	0.57		0.34		0.28	0.16
	TEMP	0.170	0.86		0.33		0.38		0.54		0.37	1.476	0.97
	TEMP 2			0.23		0.09		0.16		0.21		0.10 -1.375	0.60
	Moran's I	-0.048		-0.025		-0.083		-0.053		-0.087		-0.013

Acknowledgements -This work was supported by the FRB CESAB-GASPAR project.

Indo-Pacific areas displayed light clustering (Fig. 1). None of the investigated historical and contemporary variables were significantly related to the spatial variation in NRI once spatial autocorrelation has been accounted for with the SAR models (Table 2, Supplementary material Appendix 2, Table A3).

Labridae

The phylogenetic structure of Labridae showed high clustering values around the IAA when considering both NRI and NTI (Fig. 1), but the highest values occurred predominantly around Thailand and Malaysia peninsula. High clustering was also found in proximity of Madagascar and along the coasts of Brazil. Similar spatial patterns were found when considering only the Indo-Pacific species pool (Fig. 2). Isolation from Quaternary refugia was found to be the most important predictor of NRI (OLS: R 2 0.18; Supplementary material Appendix 2, Table A3; Fig. 3) and received high support when considering an OLS model mixing historical and contemporary factors (Supplementary material Appendix 2, Table A5). However, the relationship between NRI and isolation from Quaternary refugia was no longer significant once spatial autocorrelation was accounted for (Table 2 and Supplementary material Appendix 2, Table A3). When considering NTI, isolation from Quaternary refugia and current temperature were found to be the most important predictors of NTI (OLS: R 2 0.18 and 0.27, respectively; Supplementary material Appendix 2, Table A3; Fig. 3). However, only the isolation from Quaternary refugia displayed a significant relationship with NTI once spatial autocorrelation was accounted for (Supplementary material Appendix 2, Table A4). In addition, only the isolation from Quaternary refugia and the current level of isolation of coral reefs received high support when considering a SAR model mixing historical and contemporary factors (Table 2). phylogenetic assemblage structure was less distinguishable from random expectations (Fig. 1). Isolation from Quaternary refugia was found to be the most important predictor of both NRI and NTI, i.e. areas closer to Quaternary refugia displayed higher levels of phylogenetic clustering (OLS: R 2 0.36 and 0.51 for NRI and NTI, respectively; Supplementary material Appendix 2, Table A3 andA4; Fig. 3). This historical variable also received high support over all subset OLS and SAR models mixing historical and contemporary factors (Table 2 andSupplementary material Appendix 2, Table A5). Current isolation of coral reefs also received high support over all subset OLS and SAR models (Table 2 and Supplementary material Appendix 2, Table A5) but explained less variation in NRI and NTI (OLS: R 2 0.23 and 0.28 for NRI and NTI, respectively; Supplementary material Appendix 2, Table A3 andA4).

Chaetodontidae

The phylogenetic structure of Chaetodontidae showed different spatial patterns for NRI and NTI (Fig. 1). Similar patterns were found when only considering the species pool of the Indo-Pacific region (Fig. 2). NTI showed phylogenetic clustering in the IAA (Fig. 1), a pattern largely explained by the isolation of coral reefs from Quaternary refugia (OLS: R 2 0.37; Supplementary material Appendix 2, Table A4; Fig. 3). This historical variable also received high support over all subset OLS and SAR models mixing historical and contemporary factors (Table 2 and Supplementary material Appendix 2, Table A5). Current reef area also received high support over all subset OLS and SAR models (Table 2 and Supplementary material Appendix 2, Table A5) but explained less variation in NTI (OLS: R 2 0.25; Supplementary material Appendix 2, Table A4). In contrast, NRI had much less pronounced spatial variation. The IAA showed a weak over-dispersion whereas the Atlantic and the western Supplementary material (Appendix ECOG-01638 at www.ecography.org/appendix/ecog-01638 ). Appendix 1-2.