Susanne Boll
email: susanne.boll@uol.de

Jessica Cauchard
email: jcauchard@bgu.ac.il

Margareta Holtensdotter

Philippe Palanque Lützhöft

Michael S Feary
email: michael.s.feary@nasa.gov

Alexander G Mirnig
email: alexander.mirnig@sbg.ac.at

Keywords: Design errors, human error, safety critical systems, transportation, energy, medicine. ACM Classification Keywords, Human-centered computing~Human computer interaction (HCI), Hardware~Robustness~Safety critical systems, Hardware~Robustness~Fault tolerance~Error detection and error correction

Human error at the time of operation (i.e. when the system is in use) are implicated in most incidents involving safety critical systems. In many domains, control and command interfaces are composed of a multitude of devices and machines from different brands in different generations have been crammed together. The resultant bridging of functions across devices, the decision making, the overview, the handling of partially imprecise or conflicting information are often just offloaded to the human. Thus, there appears to be a need to shift the attention from avoiding human error (at operation time) to avoiding error during design. In this workshop, we aim to provide a forum to discuss such a paradigm shift and the implication on the methods and tools for designing and evaluating HCI technology in safety-critical environments.

Background

Safety Critical Environments, i.e., systems whose failure either endanger human life or cause drastic economic losses, form the technological backbone of today's society and are an integral part in such vastly diverse industrial sectors as automotive, aerospace, maritime, production, energy, health care, banking. Such systems are safety critical -human errors, technical failures, and malicious manipulation of information can cause catastrophic events leading to loss of life. Over many years, critical incidents have been analyzed in detail but was has been searched for was the human error [START_REF] Stratmann | Demon Hunt -The role of Endsley's demons of situation awareness in maritime accidents. Human-Centered and Error-Resilient Systems Development[END_REF].

Human machine interaction plays a crucial role in these systems, in which typically expert users are controlling and interacting with complex systems. CHI and other conferences recognize the importance of addressing the problems raised by non-classical User Interfaces. For instance, over the last decade, CHI has been featuring paper tracks on "Beyond the Desktop", addressing the issue of context of use and interactive systems that were supporting operators in performing their work. However, little to no work was targeting user interfaces for command and control interactive systems. So far, safety-critical interactions have not been in the focus of CHI yet. Novel methods and designs for interactions in large and complex settings do appear regularly at CHI. On the other hand, conferences on formal methods or software engineering address the issues raised by the design of such system with a yet limited interest for the user interface part. Similarly, conferences on human factors or cognitive engineering mainly focus on the human side of these systems addressing high-level concepts such as automation, situation awareness in those contexts, but not with a focus on the human machine interaction per se, thus 1 https://news.usni.org/2019/08/09/navy-reverting-ddgs-backto-physical-throttles-after-fleet-rejects-touchscreen-controls providing sub-optimal solutions with respect to current knowledge in the field of HCI.

The deployment of more and more complex command and control systems has not yet received widespread attention by researchers and academia. Investigations in HCI are often centered on specific single-to-narrow-purpose interface in a specific context. The multi-faceted complexity of applicationoriented domains such as aerospace, maritime, health, production, or energy (see also Figures 345) and the general and fundamental challenges they pose to human interaction did not get in the focus of CHI to a sufficient degree.

One dimension of the complexity of these safety-critical systems lies in the integration of all these devices to constitute a usable (efficient, effective, and satisfying to use) system.

Another dimension lies in the multiple stakeholders involved in the design, development, deployment, training, maintenance and certification of these systems.

The problems surrounding design of safety-critical interaction and safety-critical systems are receiving more and more public attention due to the increased deployment of these systems and the resulting failures. For instance, according to 1

Suitability for CHI

Many CHI attendees are product designers and developers vitally concerned with improving the performance of their applications. Some of them will have the opportunity to extend their application domain to safety related ones. This workshop is of immediate and practical benefit to such attendees because it allows them to hear and share the latest research problems and current solutions on this area.

To this end, this workshop will have an emphasis on case studies the organizers have been working on. This will provide useful and usable information of shared interest for both the academic researcher and the practitioners.

Workshop goals

The workshop has multiple goals in order to inform HCI research and practice for the design of large command and control systems. interface technology for ship bridges [START_REF] Stratmann | Supporting the Perception of Spatially Distributed Information on Ship Bridges[END_REF], multi-monitor environments [START_REF] Stratmann | LAME: light-controlled attention guidance for multimonitor environments[END_REF], situation monitoring in large spaces [START_REF] Gruenefeld | Visualizing out-of-view objects in headmounted augmented reality[END_REF], intensive care units [START_REF] Cobus | Multimodal headmounted display for multimodal alarms in intensive care units[END_REF]. focuses on human factors in automated public transportation [START_REF] Mirnig | Workshop on Communication between Automated Vehicles and Vulnerable Road Users[END_REF], control transitions in semi-automated vehicles [START_REF] Trösterer | What We Can Learn from Pilots for Handovers and (De)Skilling in Semi-Autonomous Driving: An Interview Study. 9th Intl[END_REF], and Machine Ethics [START_REF] Mirnig | Trolled by the Trolley Problem: On What Matters for Ethical Decision Making in Automated Vehicles[END_REF].

Philippe

Jessica Cauchard is an assistant professor in Industrial

Engineering and Management at Ben Gurion University of the Negev, Israel. Her research interests lie in the fields of human computer interaction and ubiquitous computing. She has a strong interest in how people will interact with small autonomous devices in the future, such as drones [START_REF] Cauchard | Drone.io: A Gestural and Visual Interface for Human-Drone Interaction[END_REF] in collocated situations [START_REF] Baillie | The Challenges of Working on Social Robots that Collaborate with People[END_REF]. She investigates the role of collaboration in human and robotic environments [START_REF] Baillie | The Challenges of Working on Social Robots that Collaborate with People[END_REF]. [START_REF] Lützhöft | The technology is great when it works[END_REF] and the role that automation plays in the success and failure of navigation today [START_REF] Lützhöft | On Your Watch: Automation on the Bridge[END_REF] and the role of context [START_REF] Relling | A Human Perspective on Maritime Autonomy[END_REF].

Margaretha

Michael

Pre-Workshop Plans

The call for participation (CFP) will be distributed via HCI-, Human Factors and Ergonomics Society and safety mailing lists (e.g., chi-announcements, systemsafety@lists.techfak.unibielefeld.de), social networks (e.g., Facebook groups and Twitter), as well as personal distribution lists based on workshops and conferences we have held. Accepted workshop position papers will be made available to all participants via the workshop website before the workshop to foster interactions during the workshop.

Workshop Structure

This will be a one-day workshop consisting of approximately 20 participants plus organizers. Table 1 provides an overview of the proposed workshop schedule.

Participants will be welcomed and introduced into workshop goals. The first half of the workshop-day will be dedicated to oral presentation of the position papers, reflections, and discussions on the presentations of each participant.

Participants will be provided with a 10-minute slot each including Q&A. Presentations should be short, straight to the point and convey a clear message in line with the workshop objectives.

The second half of the workshop will be dedicated to participant discussions and collaborations. Participants will discuss challenges of safety critical interaction and interfaces from various perspectives. There will be five tables each hosting a specific topic (e.g., certification, global design, human error, human as hero, conflicts and tradeoffs between properties (e.g. UX, usability, safety, dependability etc.).

Topics will be finalized based on position paper submissions and the discussion in the morning sessions. Each table will 2 https://academic.oup.com/iwc have a host (one of the organizers). After 20 minutes, every participant will move to another table to ensure that by the end of the workshop each participant has discussed each topic.

Finally, a group session will be held, in which topic hosts will present results. In a wrap up phase potentials for a joint publication and/or a special issue on the topic will be discussed.

Post-Workshop Plans

Workshop results will be communicated both to communities and a general audience including a Poster at CHI. We plan to produce a report for publication in the ACM Interactions magazine and prepare a special issue in a selected journal (e.g. Interacting with Computers 2 ) following the conference.

This will depend of the quality of the contributions and of the output of the workshop. Workshop results will be made available through the workshop website and an email list to network with others will be created.

Call for Participation

Designing Safety Critical Interactions: Hunting Down Human

Error is a one-day workshop at CHI 2020 in Hawaii, USA.

This workshop is aimed at researchers and designers in the field of human-computer interaction. In this workshop, we want to discuss practice, research and current knowledge in safety critical interactions and how to design for avoiding human error in future complex interactive systems. We will

  , in 2019 the US Navy has reported removing touch technologies from the command and control systems of battleships following the collision between USS John S. McCain and USS Fitzgerald. The architecture of John S. McCain bridge (Figure 3 of that paper) highlights the multiplicity of operator workstations and technologies.

Figure 1 .Figure 2 Figure 3

 123 Figure 1. Nurse in an intensive care station monitoring alarms (c.f. also [15])

  Provide a forum for researchers and designers of human interaction and user interfaces with an interest in safetycritical interfaces Identify commonalities and discrepencies amongst different application domains with respect to safety critical interactions and interfaces Discuss potential for transferring knowledge from usually unrelated domains such as transportation, energy and medicine Present research on potential solutions in terms of methods and processes for assessing safety of critical systems Envision new interaction paradigms for safety critical interactions taking into account a broader view of issues as, for instance [[9]] where touch interactions are enhanced with dependable mechanisms Explore engineering issues related to safety, reliability, and security properties as well as certification Consider UX factors relevant to the design of interactions within critical systems as identified in [[10]] with a focus on UX and automation. Participation The workshop is intended for HCI, Human Factors, and safety critical systems researchers and practitioners, designers and developers. Workshop candidates have to submit a position paper (four pages in the CHI extended abstract format submitted via a submission system linked via the workshop website). Organizers We have comprehensive experience in the organization of conferences, workshops and summer schools in the area of safety-critical systems. This includes events at conferences such as CHI but also dedicated events such as the ATACCS (App. and Theory of Automation in Command and Control Sys) or the international summer school on HCI in safety critical environments [[1]]. Susanne Boll is Professor of Media Informatics and Multimedia Systems in the Department of Computing Science at the University of Oldenburg, in Germany. Her research interests lie in the field human computer interaction and pervasive computing with a strong application focus on safetycritical domains. Recently she has been working on interactive

  Palanque is Professor in Computer Science at the University Toulouse 3. He is working on formal methods for engineering interactive systems and the application of such techniques to Higher Automation Levels in the field of Air Traffic Management, Interactive Cockpits of Large Civil Aircrafts [2] and Satellite Ground Segments [8]. He was chair of (Application and Theories of Automation in Command and Control Systems) ATACCS 2015 conference. Alexander Mirnig is a Research Fellow at the Center for Human-Computer Interaction at the University of Salzburg, Austria. His research interests lie in interaction design in restricted environments, interaction with automation technologies, and Philosophy of Science. His current research

  Lützhöft is a master mariner, trained at Kalmar Maritime Academy in Sweden. After leaving the sea, she studied for a Bachelor's degree in Cognitive science and a Master's in Computer Science. In 2004 she received a PhD in Human-Machine Interaction. Presently she is holding a position as Professor in the MarSafe group at the Western Norway University of Applied Sciences, and leader of the MarCATCH Research Centre. Her research interests include humancentered design and the effects of new technology

  Feary is an aerospace technologist at NASA Ames research center where he leads the Aerospace Cognitive Engineering Lab. The ACE Lab investigates methods to improve the design and evaluation of complex, safety critical systems. The work centers on formal approaches to design and evaluation of human interaction with automated systems such as ADEPT tool [[26]]. He also organized events on automation at CHI such as [[5]]. Website All the information about the workshop organization and program is published and updated on the workshop website https://sites.google.com/view/chi-ws-sci/welcome. The organizers have run several previous international events and have experience in setting up a professional Web page and advertisement of the workshop. It contains the call for participation including dates and author instructions and a link to a submission system for authors of position papers. It includes the background of each organizer and a detailed schedule of the workshop. Accepted position papers and presentations are available for download.

  discuss how the design process and methods need to change or be adapted to avoid human error in safety-critical environments already at design time. What can be learnt from other domains for the design and evaluation of autonomous vehicles. To participate, a four-page paper in the CHI extended abstract format has to be submitted via the workshop website. Position papers should cover one of the following or related topics: interactive Systems for understanding and resolving critical situations Design for safety, reliability and security in interactive systems Designing for resilience in interactive systems Metrics for evaluating interactions in complex safetycritical systems Collaboration in safety critical environments The role of simulation and models for safety critical interaction design Participatory design and ethnography for safety critical interaction design Interaction across multiple devices from multiple brands in safety-critical environments commonalities and discrepencies amongst different application domains The workshop is restricted to approximately 20 participants. Applications will be selected by workshop chairs, who will evaluate position papers based on their fit with the workshop theme, their originality, and their quality. The author of an accepted submission must attend the workshop, provide a short presentation, and register for both the workshop and for at least one day of the main conference. Deadlines Position paper: February 11, 2020 Notification: February 28, 2020 Workshop at CHI2020: April 25th/26th, 2020 More Information: https://sites.google.com/view/chi-ws-sci/welcome

Table 1 :

 1 Workshop schedule.

	10:30 -10:45	Coffee break
		Position Paper
	10:45 -	Presentations II
	12:15	(presentations 10 min
		each incl. Q&A)
	12:15 -13:30	Lunch
		Group discussions on 5
	13:30 -	tables/themes (20 minutes
	15:10	slots for each participant
		on every table)
	15:10 -15:30	Coffee break
	15:30 -16:45	Presentation of results from each table (15 min each)
	16:45 -17:00	Exploration of future work (e.g., joint publication) and wrap-up
	later	Joint workshop dinner (optional)


Côme Pasqualin
email: come.pasqualin@univ-tours.fr

SarcOptiM for ImageJ: high frequency online sarcomere length computing on stimulated cardiomyocytes

Keywords: cardiomyocyte contractility, sarcomere dynamic, video analysis, ImageJ plug-in, fast Fourier transform

Accurate measurement of cardiomyocyte contraction is a critical issue for scientists working on cardiac physiology and physiopathology of diseases implying contraction impairment. Cardiomyocytes contraction can be quantified by measuring sarcomere length but few tools are available for this and none is freely distributed. We developed a plug-in (SarcOptiM) for the ImageJ/Fiji image analysis platform developed by the National Institute of Health. SarcOptiM computes sarcomere length via FFT analysis of video frames captured or displayed in ImageJ and thus is not tied to a dedicated video camera. It can work in real time or offline, the latter overcoming rotating motion or displacement related artifacts. SarcOptiM includes a simulator and video generator of cardiomyocyte contraction. Acquisition parameters such as pixel size and camera frame rate were tested with both experimental recordings of rat ventricular cardiomyocytes and synthetic videos. It is freely distributed and its source code is available. It works under Windows, Mac or Linux operating systems. The camera speed is the limiting factor since the algorithm can compute online sarcomere shortening at frame rates above 10 kHz. In conclusion, SarcOptiM is a free and validated user-friendly tool for studying cardiomyocyte contraction in all species including human.

Introduction

Isolated cardiomyocyte (CM) contractions can be recorded and measured with two main methods: cell shortening and sarcomere shortening. The latter is probably the most common and reliable technique used to characterize isolated CM contractile performance, because it does not depend on cell shape and size [START_REF] Delbridge | Optical methods to evaluate the contractile function of unloaded isolated cardiac myocytes[END_REF]. Sarcomere shortening technique has applications in different research fields including cardiovascular physiology, pathophysiology such as heart failure, pharmacology and toxicology [START_REF] Butler | Enhanced characterization of contractility in cardiomyocytes during early drug safety assessment[END_REF][START_REF] Carillion | Overexpression of cyclic adenosine monophosphate effluent protein MRP4 induces an altered response to β-adrenergic stimulation in the senescent rat heart[END_REF][START_REF] Fowler | Decreased creatine kinase is linked to diastolic dysfunction in rats with right heart failure induced by pulmonary artery hypertension[END_REF][START_REF] Gannier | Measurements of sarcomere dynamics simultaneously with auxotonic force in isolated cardiac cells[END_REF][START_REF] Llewellyn | Minimally invasive high-speed imaging of sarcomere contractile dynamics in mice and humans[END_REF][START_REF] Song | Heart repair by reprogramming non-myocytes with cardiac transcription factors[END_REF].

Under transmission light microscopy, striated muscle cell sarcomeres show a transverse pattern due to the alternation of light (isotropic; I) and dark (anisotropic; A) bands corresponding to the very regular organization of thin filaments of actin associated with regulatory proteins such as tropomyosin and troponin (I band) and thick filaments of myosin (A band). These bands have a profile that can be assimilated to a sinusoidal curve. The frequency of this sinusoid, which represents the distance between the dark bands of the myosin filaments and therefore the sarcomere length (SL), can be extracted from Fourier spectrum analysis of the CM image. The sarcomere shortening method consists of computing the sarcomere spatial frequency and thus SL in each frame of a live or recorded video of a contracting CM. There are commercially available software for the analysis of SL and SL shortening but they are tied to dedicated video cameras and microscope systems (e.g., IonOptix and Aurora Scientific Inc). Several laboratories have developed their own software, but under licensed languages such as LabVIEW™ [START_REF] Ait-Mou | Titin strain contributes to the Frank-Starling law of the heart by structural rearrangements of both thin-and thick-filament proteins[END_REF][START_REF] Fan | Decreased myocyte tension development and calcium responsiveness in rat right ventricular pressure overload[END_REF] or MATLAB™ [START_REF] Llewellyn | Minimally invasive high-speed imaging of sarcomere contractile dynamics in mice and humans[END_REF][START_REF] Sheikh | An FHL1-containing complex within the cardiomyocyte sarcomere mediates hypertrophic biomechanical stress responses in mice[END_REF].

An open source algorithm has also been developed in Python to compute sarcomere length [START_REF] Peterson | Real-time determination of sarcomere length of a single cardiomyocyte during contraction[END_REF]. However, it is not implemented in a program and requires users to develop their own software to interface their camera with the analysis algorithm. This unfortunately makes that software very difficult to use by people without programming skills.

The aim of our work was to provide scientists working on CM -or any other structure presenting a striated pattern (e.g., transverse tubules, ryanodine receptors distribution, collagen structure, etc.)with powerful, ultrafast and accurate software compatible with most of the video cameras and finally not affected by cell displacement and rotation in the field. Moreover, this software has to be easy and ready to use, free and open source. Thus, we developed SarcOptiM, a plug-in for the open source microscopy image analysis software of the NIH: ImageJ. It has two operating modes. Online mode allows the real time analysis and display of the contraction of a cell along a line (1 pixel thick or more) drawn along its longitudinal axis (i.e., on cell axis mode). Offline mode is dedicated to the analysis of pre-recorded videos of contracting CM. This mode can be used in two ways: on cell axis mode, as above or on entire frame, which extracts data from the entire video image. SL measurements with the on entire frame mode avoid artifacts due to rotation and/or movement of the cell.

SarcOptiM has been validated and packaged with a number of control features including a means of constructing synthetic videos of a model cell contracting according to user defined parameters.

SarcOptiM has been tested under Linux, Windows and Mac OS. It is freely available in the plug-in section of ImageJ website and on http://pccv.univ-tours.fr/ImageJ/SarcOptiM/.

Materials and methods

Isolation of rat ventricular cardiomyocytes

All protocols have been approved by the local ethical committee (Comité d'Ethique en Expérimentation Animale Val de Loire, Tours, France). Adult male Wistar rats were anesthetized with pentobarbital (60 mg/kg). The heart was rapidly removed and coronary circulation was retrogradely perfused through the aorta. Enzymatic digestion was performed by perfusion of 0.

Experimental setup and protocol

Cardiomyocytes were placed in a perfusion chamber mounted on an inverted microscope (Nikon Diaphot 300) for online sarcomere analysis and video recording of contraction at 25°C. Myocytes were superfused with Tyrode's solution containing (in mM): 140 NaCl, 5.37 KCl, 1.36 CaCl 2 , 1 MgCl 2 , 0.33 NaH 2 PO 4 , 10 HEPES, 11 glucose, at pH 7.4, adjusted with NaOH. Myocytes were electrically field stimulated at 1 Hz with square wave pulses (80 mA, 2 ms) delivered through a pair of platinum electrodes.

Recording of cardiomyocyte contraction

The videos of rat left ventricular myocytes contracting under electrical stimulation at 1 Hz were captured with an IDS UI-1220LE-M-GL camera (Imaging Development Systems, Germany). Online experiments in ImageJ used the plug-in HF_IDS_Cam (available on ImageJ website). Video recording for subsequent offline analysis used the camera supplier software uEye Cockpit. The camera was connected to an USB port of a PC workstation (Xeon E3 1241v3 3.5 GHz processor) running under either Linux or Windows 7 (64 bits) operating systems.

Synthetic videos of a cardiomyocyte contraction simulation

Each sarcomere measurement mode of SarcOptiM has been validated with synthetic videos of a modeled contracting CM. These were created with the Video synthesis tool which is implemented in SarcOptiM. In these synthetic videos, frame rate, pixel size and CM features (length, width, resting SL, sarcomere shortening and contraction/relaxation speed factor), as well as CM movement and rotation in the video field can be user defined to match particular experimental preparations and test user hardware. The equation:

1 ) exp( min + × - × - - × = SF t SF t t e SL SL
(with SL t : SL at t time; SL min : minimum sarcomere length at maximum peak shortening; t: time; SF: contraction/relaxation speed factor which adjusts the theoretical model to fast or slow twitches) is used to model the CM contraction. In our examples the standard parameters were as follows: resting SL: 1.8 µm, sarcomere shortening: 5 % of the resting SL, pixel size: 0.3 µm, video frame rate equivalent: 100 Hz, number of frames: 40 (i.e., a total equivalent of 400 ms record), angle of the CM in the frame: 30° from the horizontal, contraction/relaxation speed factor: 1. Example of synthetic CM generated by this module is available in the Data Supplement (Video_1.mp4).

Setting up and use

To install SarcOptiM in ImageJ:

1. Unzip the SarcOptiM.zip file; 2. Put the SarcOptiM folder into the "ImageJ\plugins" folder; 3. Put the SarcOptiM.ijm file into the "ImageJ\macros\toolsets" folder.

The user guide on our institutional website and on the ImageJ website contains more information and a video demonstration of its use is available in the Data Supplement (Video_2.mp4). It is important to note that another plug-in is necessary to acquire video flow from digital, e.g., HF_IDS_Cam and Webcam Capture, or analog e.g., PixelSmart Frame Grabbers cameras.

Statistics

All boxplots indicate minimum, first quartile, median and mean, third quartile and max values. All statistics have been performed with R and SigmaStat. For the comparison between groups, ANOVA tests were performed. Differences are considered significant when the P value is inferior to 0.05.

Results

Analysis algorithm description and outputs

In on cell axis mode (Figure 1), the sarcomere measurement algorithm searches for a peak in the fast Fourier transform (FFT) of the grey level profile of the myocyte longitudinal axis along the line positioned on the image by the user (Fig. 1A,B). The position of the peak located in the FFT spectrum within the limits for SL values defined by the user is determined (Fig. 1C). Then given the pixel size, the sarcomere length is calculated.

For an analysis with on entire frame mode, the algorithm is similar, except that the FFT is calculated over the entire image and is not confined to the myocyte. The peak is sought with native "find maxima" ImageJ function in a 2D plane within the limits for SL values defined by the user (Fig. 2). Then given the pixel size, the x-y coordinates of the peak and its Euclidian distance from the center of the Fourier spectrum, the SL is calculated.

At the end of the sarcomere measurement computation, each SL value is plotted versus time in a new window (Fig. 1D,2C). Time is determined by video frame rate. The XY data can be saved as a comma separated values file (.csv) or copied into the clipboard for further analysis.

For a more complete understanding of the analysis, please consult the source code.

Accuracy of the SL measurement with different pixel sizes

Since the accuracy of sarcomere measurement depends on the spatial resolution of the acquired image, the effect of pixel size upon SL parameters has been investigated with the on cell axis mode of SarcOptiM. In this test, we used a synthetic video of a mathematically modeled CM contraction with the standard parameters (see Materials and methods) and six realistic pixel sizes. The sarcomere measurement on each frame during the contraction and relaxation was compared to the value assigned to that point in the model. Absolute differences between each measured and each theoretical value are shown as boxplot in Fig. 3A. For a pixel size between 0.20 and 0.35 µm, the error of the measurement is, in the worst case, inferior or equal to 0.005 µm. For a pixel size of 0.40 and 0.45 µm, the measurement error lies between 0.006 and 0.007 µm. These values are far below the pixel size since there are obtained with a frequency analysis by FFT and not by a simple metric measurement [START_REF] Gannier | Measurements of sarcomere dynamics simultaneously with auxotonic force in isolated cardiac cells[END_REF].

Comparison between on cell axis and on entire frame modes of analysis

The on cell axis mode is much faster than the on entire frame mode because the latter requires a two-dimensional FFT calculation instead of a single one. However, it could fail if the contracting cell moves and leaves the measurement axis. Analysis mode on entire frame avoids this problem since no measurement axis is required as illustrated by the video of a rat ventricular CM moving and rotating in the field (see Data Supplement (Video_3.mp4 and Video_4.avi)). Moreover, multiple dead cells in the analyzed field do not affect the SL measurement. However, this mode restricts application to offline analysis of pre-recorded experimental videos since actual performances of current computer are insufficient to allow online analysis. To compare the quality of analysis in both modes, two synthetic videos with standard parameters (see Materials and methods) were used. In the second video, a rotary motion from 30° down to the horizontal was applied to the CM. The first video was analyzed with on cell axis and on entire frame modes. The second video was analyzed with the on entire frame mode alone. As above, SL data obtained through a contraction-relaxation cycle were compared to their model values and the results are shown in Fig. 3B. The on cell axis mode allows the best accuracy of measurement with a maximum error in the worst case less than 0.005 µm. With the on entire frame mode, the worst case error is slightly higher since it can reach 0.009 µm due to the pixel interpolation when the cell axis is not exactly horizontal or vertical. However, with this mode, the SL measurement is not affected and the maximum error is not significantly increased by the cell rotation in the visual field (Fig. 3B and3C). Thus, the on cell axis analysis mode is recommended in standard conditions. The on entire frame analysis mode has to be used when the CM moves or rotates in the field despite this will result in a slightly higher variability of SL measurement.

A supplemental tool based on the offline on entire frame mode has also been developed to simultaneously measure contractions of several cardiomyocytes. It should be noted that this tool can be used only if the cells do not have exactly the same orientation in the video field. This is required to separate and distinguish the peaks corresponding to each cell in the FFT spectrum.

Effect of the sampling frequency upon the quality of the measurement of rat cardiomyocyte contractions under basal conditions and following β-adrenergic stimulation with isoproterenol

Several video capture frequencies were tested to determine the optimal frame rate for sarcomere measurement of a rat ventricular CM before and after superfusion of 100 nM isoproterenol (known to increase contraction kinetic and amplitude). Examples of sarcomere measurements (on cell axis mode) in control conditions at video frame rates of 25, 50, 100, 250, 500, 1000 Hz are shown Fig. 4. The optimal frequency was determined by measuring for each rate the minimum sarcomere length (minSL) and maximum sarcomere shortening speed (dSL/dt max ; Fig. 5A,B). The acquisition frequency is considered sufficient when minSL and dSL/dt max vary by less than 5 % from the values determined at 1000 Hz. In control conditions, 100 Hz is enough to record minSL (1.708 vs. 1.708 µm at 1000 Hz) and dSL/dt max (-2.26 vs. -2.27 µm.s -1 at 1000 Hz). However, the sampling rate must be increased to 250 Hz in the presence of isoproterenol to obtain an accurate dSL/dt max (minSL: 1.576 vs. 1.576 µm at 1000 Hz and dSL/dt max : -6.68 vs. -6.98 µm.s -1 at 1000 Hz). The effect of 100 nM isoproterenol on the contraction of a rat CM recorded at 250 Hz is shown in Fig. 5C,D. The increases of sarcomere shortening and of contraction and relaxation rates are clearly visible (Fig. 5D). Therefore, with this preparation and under these experimental conditions a frame rate of 250 Hz is recommended for SL measurements but this parameter has to be optimized for other experimental conditions.

Discussion and conclusions

SarcOptiM is the first open source, easy to use and freely available software plug-in for the analysis of cardiomyocytes contractions with the sarcomere shortening method. We validated the measurement algorithms with synthesized videos with defined parameters. Tests were also conducted on isolated rat ventricular myocytes.

Versatility

SarcOptiM works with any analog or digital camera that can be interfaced with ImageJ, Fiji and Micromanager as shown by examples available on the software download webpage. This is not necessarily the case for licensed software which may work only with dedicated cameras. A nonexhaustive list of cameras working with ImageJ is available on the ImageJ website (Plugins>Acquisition section). Another list for Micromanager is available on micromanager website device section. Thus, a camera can be chosen to meet the requirements of the experiment, in particular with regards to the best resolution-sensitivity-speed compromise. Moreover, SarcOptiM allows sarcomere measurement on pre-recorded videos. This offline analysis is useful for experiments requiring several analyzes or if the CM moves or rotates in the optical field. Finally, the total analysis time can be significantly reduced with SarcOptiM. Indeed, the analysis could also be simultaneously performed on several cells with the offline multiple cells on entire frame mode, provided that cells do not have exactly the same orientation in the video field.

Performance

The reliability of the sarcomere measurement provided by SarcOptiM has been demonstrated by tests on synthetic videos. Measurements can be performed as long as CM sarcomeres are visible on the video, even in low light conditions. In addition, they are not affected by light oscillations as the calculations are done on the image FFT and not on their brightness. The limitation is sufficient greyscale definition to separate signal-noise in the FFT (Fig. 1C). With these features, the use of midrange cameras, such as the IDS UI-1220LE-M-GL, is possible. This camera is able to record sarcomere shortening at frequencies above 1000 Hz, although we found that a sampling rate of 250 Hz is usually enough for rat ventricular cardiomyocytes (Fig. 5). For other cell types, such as skeletal muscle, which require a high sampling rate, the measurement algorithm is not a limiting factor for online computing: at full speed, it can calculate SL at sampling rates far above 10 kHz.

In addition to its free distribution and versatility, SarcOptiM presents several other advantages since it is integrated into an image processing software. It is thus possible to work on the video as well as on images, to adjust brightness or contrast, to define areas of interest or other processing. With this plug-in, sarcomere measurement can be done whatever the orientation of the cell in the video frame, unlike most licensed software and the Python algorithm (9) which require a perfect horizontal orientation of the cell. Moreover, it allows an easy adjustment of the measuring axis during the analysis.

A model of myocyte contraction is included in SarcOptiM, which is another asset of the software. This is used to construct video simulations with user defined parameters. Users can thus test, evaluate and optimize pixel size, video frame rate, upload time and computer performance for their own experimental conditions and hardware configuration.

SarcOptiM has been developed to work under Windows, Mac OS and Linux operating systems; however, under identical computing conditions we found that the best performance of the algorithm was obtained in Linux.

Known limits

Native video import in ImageJ is limited to AVI encoded in MJPEG or images series e.g., TIFF series. However, additional plug-ins can open other video formats e.g., MovieIO. Moreover, given the ability of ImageJ to analyze video, it is likely that the number of importable video formats will increase. A limitation of SarcOptiM is the impossibility to receive a synchronization signal, for example to indicate the moment when electrical stimulation is applied to the cell.

Perspectives

This open-source plug-in developed in ImageJ macro language and Java can be modified by anyone to improve existing functions or add new ones such as analysis with autocorrelation function or measurement method by edge detection.

Analysis with on entire frame mode of SarcOptiM cannot currently be used for real time analysis since there is insufficient processor power for the online computation of the two dimensional Fourier spectrum (Fig. 2). In the future with improved processor performances, not only should this be possible but should also allow the analysis of several contracting isolated myocytes at the same time as well, whatever their orientations in the visual field and without motion artifacts.

Figure legends

Figure 1 :

 1 Figure 1: Flow diagram of the algorithm for SarcOptiM on cell axis analysis. (A) An example of an input image opened with ImageJ. The white line represents the axis positioned for sarcomere measurement. (B) Grey level profile along the axis of measurement. (C) Fourier spectrum of the grey level profile. Double headed arrow indicates the limits between which the algorithm searches for the peak. This interval is user defined as the minimum and maximum sarcomere lengths set before the analysis. The vertical arrow shows the detected peak corresponding to sarcomere spatial frequency in A. (D) Example of output plot representing sarcomere lengths vs. time.

Figure 2 :

 2 Figure 2: Flow diagram of the algorithm for SarcOptiM on entire frame mode. (A) An example of the input image opened with image J. (B) 2D Fourier spectrum of the image (left) and 3D surface plot of the FFT spectrum (right). Rings indicate the limits set for searching the peak defined by the user as minimum and maximum sarcomere lengths before the analysis. Arrows show the detected peak corresponding to sarcomere spatial frequency in this frame. (C) Example of output plot representing sarcomere lengths vs. time Figure 3: (A) Absolute error of the sarcomere length measurement corresponding to the difference between the measured and the model values during a simulated cardiomyocyte contraction were recorded for different pixel sizes with on cell axis mode. n = 40 frames for runs for each pixel size. (B) Effect of different analysis modes on absolute error of the sarcomere length measurement during a simulated cardiomyocyte contraction with or without myocyte rotation. (n = 40 frames). L: on cell axis mode without cell rotation, F: on entire frame mode without cell rotation, FR: on entire frame mode with cell rotation. Pixel size was 0.3 µm. In panels (A) and (B), boxplots indicate minimum, first quartile, median and mean, third quartile and max values for each condition. *: p<0.05 with ANOVA and Bonferroni post-hoc t-test; NS: non-significant. (C) Example of offline sarcomere length measurements with both on entire frame (grey line) and on cell axis (black line) modes during cell contraction and rotation. The video used for these measurements is available in the Data Supplement (Video_4.avi). Note that the entire frame mode allows undisturbed sarcomere length measurement during the cell rotation, especially during the diastole.

Figure 4 :

 4 Figure 4: Effect of video frame rate on sarcomere length measurement during contraction of a rat left ventricular cardiomyocyte electrically stimulated at 1 Hz under basal conditions (on cell axis mode). (A-F) Sarcomere length measurements at frame rates of 25, 50, 100, 250, 500 and 1000 Hz. Pixel size was 0.3 µm.

Figure 5 :

 5 Figure 5: Measurement of rat left ventricular cardiomyocyte contractions electrically evoked at 1 Hz under basal conditions and following superfusion by 100 nM isoproterenol (iso) with on cell axis mode. (A-B) Effect of video sampling rate on the measurement of minimum sarcomere length (minSL; A) and maximum sarcomere shortening speed (dSL/dt max ; B) in control conditions (grey) and in the presence of isoproterenol (black). (C-D) Effect of isoproterenol on the contraction recorded at a video frame rate of 250 Hz and a pixel size of 0.3 µm. (C) Continuous recording of sarcomere measurement during the superfusion of isoproterenol (bar above the trace). (D) Examples of sarcomere shortening before and after superfusion of isoproterenol (arrows in C). 's' indicates the time of electric stimulation.

  Figure 1

  1 UI/mL Liberase™ Research Grade in Krebs-Ringer-Bicarbonate solution (in mM: 35 NaCl, 25 NaHCO 3 , 4.75 KCl, 1.19 KH 2 PO 4 , 16 Na 2 HPO 4 , 134 sucrose, 10 HEPES, and 10 glucose, pH adjusted to 7.4) at 37°C. At the end of the digestion, ventricles were separated and gently mechanically dissociated with Pasteur pipettes.

Acknowledgments

This work was financially supported by the Ministère de l'Enseignement Supérieur et de la Recherche, the Centre National de la Recherche Scientifique and the Région Centre -Val de Loire.

Thanks to Stemmer-Imaging (France) for providing us the IDS UI-1220LE-M-GL camera, to Ian Findlay for his critical comments and correcting English, and to Samantha Dellal for proof-reading.

Disclosures

No conflicts of interest, financial or otherwise, are declared by the authors.

Author contributions

Endnote

At the request of the authors, readers are herein alerted to the fact that additional materials related to this manuscript may be found at the institutional website of one of the authors, which at the time of publication they indicate is: [http://pccv.univ-tours.fr/ImageJ/SarcOptiM/]. These materials are not a part of this manuscript, and have not undergone peer review by the American Physiological Society (APS). APS and the journal editors take no responsibility for these materials, for the website address, or for any links to or from it.


Adriane Aupic-Samain
email: adriane.samain-aupic@imbe.fr

Virginie Baldy
email: virginie.baldy@imbe.fr

Ninon Delcourt
email: ninon.delcourt@imbe.fr

Paul Henning Krogh

Thierry Gauquelin
email: thierry.gauquelin@imbe.fr

Catherine Fernandez
email: catherine.fernandez@imbe.fr

Mathieu Santonja
email: mathieu.santonja@imbe.fr

Addresses

Paul Henning Dr

Krogh

D R Mathieu

Dr Maria Briones

Water availability rather than temperature control soil fauna community structure and preypredator interactions

Keywords: Climate change, Collembola, functional trait, mite, soil moisture, springtail, topdown control, trophic interaction

The ongoing climate change may strongly impact soil biodiversity with cascading effects on the processes they drive. Thus, it is of prime interest to improve our knowledge about responses by soil organisms such as collembolans to expected shifts in environmental conditions by considering communities comprising both detritivores and predators.

2. The aim of the present study was to evaluate how simulated climate change and predation under laboratory conditions alter a collembolan community. 3. To infer the impact of climate change, we applied a decreased level of soil moisture (60% vs. 30% soil water holding capacity) and an increasing air temperature (15 °C vs. 25 °C) to a collembolan community constituted by four species (Folsomia candida, Protaphorura fimata, Proisotoma minuta and Mesaphorura macrochaeta) exhibiting distinct functional traits, e.g. body size and furca presence, in presence or absence of a predatory gamasid Acari (Stratiolaelaps scimitus) during two months in a microcosm experiment. 4. We observed that decreasing soil moisture altered the collembolan community with species-specific responses. Interaction between soil moisture, temperature and predation indicates that low soil moisture reduced total collembolan abundance especially i) by suppressing the positive effect of increasing temperature and ii) by increasing the predatory control on collembolan abundance.

Introduction

In terrestrial ecosystems, soil biodiversity drives biogeochemical cycles [START_REF] Bardgett | The biology of soil: a community and ecosystem approach[END_REF][START_REF] Berg | Litter Decomposition: A Guide to Carbon and Nutrient Turnover[END_REF][START_REF] Hättenschwiler | Biodiversity and litter decomposition Accepted Article This article is protected by copyright. All rights reserved in terrestrial ecosystems[END_REF] supporting soil fertility [START_REF] Scheu | Interactions between microorganisms and soil micro-and mesofauna[END_REF][START_REF] Gobat | Le sol vivant: bases de pédologie, biologie des sols[END_REF], plant growth (Van der Putten, Vet, Harvey & Wäckers, 2001) and overall ecosystem functioning (Wardle, Bonner & Barker, 2002;[START_REF] Gobat | Le sol vivant: bases de pédologie, biologie des sols[END_REF]. Among soil organisms, Collembola is a widespread group of microbi-detritivore organisms [START_REF] Hopkin | Biology of the Springtails: (Insecta: Collembola)[END_REF]. They play a crucial role in nutrient cycling by regulating soil microbial communities [START_REF] Hättenschwiler | Biodiversity and litter decomposition Accepted Article This article is protected by copyright. All rights reserved in terrestrial ecosystems[END_REF][START_REF] Chahartaghi | Feeding guilds in Collembola based on nitrogen stable isotope ratios[END_REF] and by micro-fragmenting litter [START_REF] Gobat | Le sol vivant: bases de pédologie, biologie des sols[END_REF]. Collembola also play a key role in structuring the soil food web, being both microbial consumer and prey of several predators including spiders [START_REF] Lawrence | Spider predation on forest-floor Collembola and evidence for indirect effects on decomposition[END_REF]Vucic-Pestic, Birkhofer, Rall, Scheu & Brose, 2010), centipedes [START_REF] Günther | Variations in prey consumption of centipede predators in forest soils as indicated by molecular gut content analysis[END_REF][START_REF] Kalinkat | Habitat structure alters top-down control in litter communities[END_REF] and predatory Acari [START_REF] Koehler | Predatory mites (Gamasina, Mesostigmata)[END_REF][START_REF] Schneider | Top-down control of soil microarthropods -Evidence from a laboratory experiment[END_REF]Thakur & Eisenhauer, 2015;[START_REF] Aupic-Samain | Tree litter identity and predator density control prey and predator demographic parameters in a Mediterranean litter-based multi-trophic system[END_REF]. However, Collembola are strongly sensitive to environmental parameters such as soil humidity and air temperature [START_REF] Harte | Effects of manipulated soil microclimate on mesofaunal biomass and diversity[END_REF][START_REF] Hopkin | Biology of the Springtails: (Insecta: Collembola)[END_REF][START_REF] Lindberg | Population responses of oribatid mites and collembolans after drought[END_REF][START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF]. Thereby, the ongoing climate change, such as reduced precipitation and increasing temperature predicted in the temperate and Mediterranean regions [START_REF] Ipcc | Climate change 2013: The physical science basis: working group I contribution to the fifth assessment report of the intergovernmental panel on climate change[END_REF][START_REF] Dubrovský | Multi-Accepted Article This article is protected by copyright. All rights reserved GCM projections of future drought and climate variability indicators for the Mediterranean region[END_REF], may strongly impact Collembola communities by altering species demographic parameters (e.g. reproduction, growth rate and survival, [START_REF] Blankinship | A meta-analysis of responses of soil biota to global change[END_REF];

Accepted Article

This article is protected by copyright. All rights reserved [START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF] and trophic interactions within the soil food web (Tylianakis, Didham, Bascompte, & Wardle, 2008;Van der Putten, Macel & Visser, 2010) with cascading effects on overall ecosystem functioning (Thakur et al., 2015;[START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF].

Despite a growing interest to predict the responses of organisms and the processes they drive to future climatic conditions, only few studies focus on soil organisms. Under elevated temperature, ectothermic organisms such as Collembola and their predators generally increase their activities (e.g., reproduction, growth rate, mobility, nutrition) within their thermal limits due to a higher metabolic demand [START_REF] Gillooly | Effects of size and temperature on metabolic rate[END_REF][START_REF] Rall | Temperature, predator-prey interaction strength and population stability[END_REF]. For instance, [START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF] reported an increase of collembolan abundance (Folsomia candida) from low temperature (15 °C) to moderate temperature (20 °C) followed by a strong reduction at elevated temperature (25 °C) exceeding their thermal limit in a 4-week microcosm experiment. In addition, altered climatic conditions could modify the outcome of predator-prey interactions (Thakur, Künne, Griffin & Eisenhauer, 2017;[START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF]. For example, [START_REF] Lang | Effects of environmental warming and drought on size-structured soil food webs[END_REF] reported in a 7-week microcosm experiment that both increasing temperature and decreasing soil moisture reduced Collembola prey biomass (Lepidocyrtus cyaneus and Isotoma viridis)

due to an increased consumption rate of a predatory Acari (Hypoaspsis aculeifer). While numerous studies provided clear evidence of negative effects of drought conditions (e.g., [START_REF] Lindberg | Effects of experimental irrigation and drought on the composition and diversity of soil fauna in a coniferous stand[END_REF]Tsiafouli, Kallimanis, Katana, Stamou & Sgardelis, 2005;[START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF] and of combined warmer and dryer conditions [START_REF] Petersen | Collembolan communities in shrublands along climatic gradients in Europe and the effect of experimental warming and drought on population density, biomass and diversity[END_REF]Xu, Kuster, Günthardt-Goerg, Dobbertin & Li, 2012) on collembolan populations during field experiments, only few studies used laboratory microcosm experiments. Moreover, these studies focused on the responses of a single or two collembolan species, which do not reflect natural communities and therefore limit extrapolation of the results from lab to field conditions. Experimentally controlled conditions mimicking, as far as possible, the natural conditions, are necessary to decipher the mechanisms responsible for such negative alterations.

Ecological traits, including functional, morphological, physiological or phenological traits, strongly determine the performance of soil organisms (Violle et al., 2007). Species that exhibit distinct functional traits could therefore differently respond to environmental factors [START_REF] Makkonen | Traits explain the responses of a sub-arctic Collembola community to climate manipulation[END_REF][START_REF] Ripley | Linking species, traits and habitat characteristics of Collembola at European scale[END_REF]. Body size appears to be strongly influenced by shifts in climatic conditions [START_REF] Mcgill | Rebuilding community ecology from functional traits[END_REF]. The temperature-size rule (TSR) [START_REF] Atkinson | Temperature and organism size-a biological law for ectotherms? Adv. Accepted Article This article is protected by copyright[END_REF] predicts that small body size is an adaptive advantage in response to warmer conditions (Reuman, Holt & Yvon-

Accepted Article

This article is protected by copyright. All rights reserved [START_REF] Reuman | A metabolic perspective on competition and body size reductions with warming[END_REF][START_REF] Lindo | Warming favours small-bodied organisms through enhanced reproduction and compositional shifts in belowground systems[END_REF] since small body size is associated with a reduction of the metabolic costs that occur with thermal constraints. In addition, a smaller body size of a collembolan could be favoured over larger ones under dryer conditions since they could survive in sheltered microhabitats [START_REF] Kalinkat | Habitat structure alters top-down control in litter communities[END_REF][START_REF] Aupic-Samain | Tree litter identity and predator density control prey and predator demographic parameters in a Mediterranean litter-based multi-trophic system[END_REF] including deeper soil layers [START_REF] Ojala | Dispersal of microarthropods in forest soil[END_REF][START_REF] Pflug | Influence of drought and litter age on Collembola communities[END_REF]. However, in a 60-day microcosm experiment, Thakur et al., (2017) reported that the larger collembolan F. candida outperformed the smaller collembolan Proisotoma minuta under warmer conditions as gamasid mites H. aculeifer and Stratiolaelaps scimitus (formerly H. miles) exhibited a higher predation effect on small compared to large preys. In addition to the key role played by body size, the furca, i.e., the collembolan jumping organ, allows them to escape predators [START_REF] Bauer | Habitat dependent differences in the flight behaviour of Collembola[END_REF][START_REF] Hopkin | Biology of the Springtails: (Insecta: Collembola)[END_REF]. Thus, in a predator-prey system, some Collembola could respond differently to the interactive effects of decreasing soil moisture and increasing temperature according to their different ability to escape predation due to some functional traits including both body size [START_REF] Kalinkat | Habitat structure alters top-down control in litter communities[END_REF]Thakur et al., 2017) and furca presence.

However, no previous study attempted to evaluate the impact of both decreasing soil moisture and increasing temperature on a collembolan community and its response to predation, even though this type of experimentation could improve our mechanistic knowledge of soil microarthropod responses to the ongoing climate change.

To fill this gap, we investigated how low soil moisture (60% vs. 30% soil water holding capacity), elevated atmospheric temperature (15°C vs. 25°C) and their interactions alter a collembolan community artificially constituted by four species (F. candida, Protaphorura fimata, P. minuta and Mesaphorura macrochaeta) with distinct functional traits such as body size and furca size in an 8-week factorial microcosm experiment. In addition, we investigated how the presence of a predatory Acari (Stratiolaelaps scimitus) alters this collembolan community in combination with environmental pressures. Firstly, we hypothesize that decreasing soil moisture can reduce collembolan abundances as water availability is generally the most constraining environmental condition for soil organisms in temperate and Mediterranean ecosystems [START_REF] Lindberg | Population responses of oribatid mites and collembolans after drought[END_REF][START_REF] Kardol | Climate change effects on soil microarthropod abundance and community structure[END_REF]. Secondly, we hypothesize that increasing temperature will increase collembolan abundances under optimal soil moisture conditions [START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF].

Thirdly, we hypothesize that decreasing soil moisture can enhance the predatory control of the collembolan community since predatory Acari are less sensitive to desiccation than their collembolan prey [START_REF] Kardol | Climate change effects on soil microarthropod abundance and community structure[END_REF][START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF]. Fourthly, we hypothesize that increasing temperature will strengthen the predatory control of the collembolan community

Accepted Article

This article is protected by copyright. All rights reserved due to increasing activity leading to a higher encounter probability between prey and predator (Thakur et al., 2017;[START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF].

Material and Methods

Litter and soil collection

Litter and soil material used as substrate for soil microarthropods were collected at the O 3 HP (Oak Observatory at OHP) experimental field site located in the Luberon Natural Regional Park (43°45′34.26″N, 5° 17′57.84″E; 650 m a.s.l), in Provence, SE France. This site is covered by a Mediterranean oak forest dominated by the downy oak (Quercus pubescens Willd.) and Montpellier maple (Acer monspessulanum L.). Senescent leaves of A. monspessulanum were sampled from different trees in November 2017 during the litterfall period. These leaves were placed in litterbags (4-mm mesh size) and disposed at the soil surface for 2 months (from middle November to middle January) in order to allow microbial colonization [START_REF] Swift | Decomposition in[END_REF]. After retrieval, the litter samples were pooled, dried at room temperature, frozen twice at -18 °C for 48 h in order to remove only fauna. This method of defaunation has been previously used efficiently to remove soil fauna with a minimal effect on the microbial community [START_REF] Poll | Low amounts of herbivory by root-knot nematodes affect microbial community dynamics and carbon allocation in the rhizosphere[END_REF]Thakur et al., 2017). The leaf litter characteristics of A. monspessulanum were determined according to the protocols described in [START_REF] Aupic-Samain | Tree litter identity and predator density control prey and predator demographic parameters in a Mediterranean litter-based multi-trophic system[END_REF]. The leaf litter has a C: N ratio of 53 ± 0.4, a water holding capacity of 70% and a specific leaf area of 177 cm 2 g -1 .

Soil cores of 5 cm diameter × 5 cm depth were sampled in November 2017, sieved through a 2 mm mesh and frozen twice for 48 h to remove the remaining soil fauna, in particular immobile forms such as eggs and pupae [START_REF] Poll | Low amounts of herbivory by root-knot nematodes affect microbial community dynamics and carbon allocation in the rhizosphere[END_REF]Thakur et al., 2015). Soil samples were autoclaved twice for 24 h between the two cycles at 1 atm and 121 °C in order to eliminate soil invertebrates and microorganisms [START_REF] Alef | Methods in applied soil microbiology and biochemistry[END_REF]Trevors, 1996;[START_REF] Fernandez | Allelochemicals of Pinus halepensis as drivers of biodiversity in Mediterranean open mosaic habitats during the colonization stage of secondary succession[END_REF]. Soil has a C: N of 12.4 ± 1.5, organic matter of 19.2 ± 0.6% and a pH of 7.1 ± 0.05. Soil and litter were stored in a dark room at ambient temperature until the start of the experiment.

Mesofauna collection

The experiment was conducted using two well-represented soil arthropod groups from the leaf litter of Mediterranean forests: a gamasid predator and collembolan prey [START_REF] Poinsot-Balaguer | Contribution à l'étude des Collemboles des Maures (Var-France)[END_REF][START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF]Thibaud, 2017). Due to i) the difficulty to

Accepted Article

This article is protected by copyright. All rights reserved easily distinguish several species from the same genus in the field, such as for example F. candida and F. fimetaria that coexist in natura, ii) the difficulties in maintaining laboratory cultures of collembolans collected in the field, and iii) the high number of individuals necessary to perform the experiment (i.e., 5120 Collembola and 640 Acari individuals), we decided to use 5 microarthropod species frequent in Mediterranean oak forests (4 Collembola and 1 Acari) from laboratory cultures [START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF]personal observations).

The gamasid mite Stratiolaelaps scimitus (Acari: Laelapidae) was selected as representing predators. S. scimitus is an ubiquitous species [START_REF] Karg | Räuberisch lebende milben als teil des antiphytopathogenen potentials im Accepted Article boden[END_REF] known as predator of Collembola [START_REF] Koehler | Predatory mites (Gamasina, Mesostigmata)[END_REF][START_REF] Aupic-Samain | Tree litter identity and predator density control prey and predator demographic parameters in a Mediterranean litter-based multi-trophic system[END_REF]. It was fed Folsomia candida during rearing.

Four collembolan species were selected according to two morphological traits: body size (large vs. small) and furca (presence vs. absence). Folsomia candida Willem, 1902 (Collembola: Isotomidae), and Protaphorura fimata Gisin, 1952 (Collembola: Onychiuridae) (GenBank acc. no. MN519200) were selected as large prey species with and without furca, respectively (Table S1). Proisotoma minuta Tullberg, 1871 (Collembola: Isotomidae) and Mesaphorura macrochaeta Rusek, 1976 (Collembola: Onychiuridae) (GenBank acc. no. MN525426) were chosen as small prey species with and without furca, respectively (Table S1). These hemi-and euedaphic (i.e., intermediate and deep soil-living) species are ubiquitous, known as microbi-detritivorous species and frequently used in laboratory experiment [START_REF] Fountain | Folsomia candida (Collembola): a "standard" soil arthropod[END_REF][START_REF] Staaden | Olfactory cues associated with fungal grazing intensity and secondary metabolite pathway modulate Collembola foraging behaviour[END_REF]Thakur et al., 2017). Folsomia candida and S. scimitus were obtained from permanent laboratory cultures at Aix-Marseille University, Marseille, France, while M. macrochaeta, P. fimata and P. minuta were obtained from permanent laboratory cultures at Dep. of Bioscience, Aarhus University, Silkeborg, Denmark. All Collembola species were fed ad libitum with dry yeast pellets (Arkopharma ® ).

The five selected species were reared separately in plastic boxes (5.5 cm diameter × 9 cm height) containing a flat mixture of plaster of Paris and activated charcoal in a 9:1 ratio, permanently water saturated. Since Acari and Collembola have different generation times which also depend on the environmental conditions such as temperature and pH [START_REF] Folker-Hansen | Effect of dimethoate on body growth of representatives of the soil living mesofauna[END_REF][START_REF] Fountain | Folsomia candida (Collembola): a "standard" soil arthropod[END_REF][START_REF] Park | Effect of laboratory culture conditions on population growth of Proisotoma minuta (Tullberg) (Collembola: Isotomidae)[END_REF], individuals from each species with similar body size were carefully selected in order to synchronize the age of these organisms for the experiment. Prior to the start of the experiment, all individuals were starved for 48 h.

Accepted Article

This article is protected by copyright. All rights reserved

Experimental setup

We tested the effects of two temperatures (15 °C or 25 °C), two soil moisture conditions (60% or 30% soil water holding capacity WHC) and two levels of predation pressure either presence or absence of a S. scimitus on the population performance of the four Collembola species and the predator. Each combination was replicated eight times and then led to the construction of 64 microcosms, i.e., 2 temperatures × 2 moisture conditions × 2 predator pressures × 8 replicates. Ten g of autoclaved soil (equivalent dry mass) were placed into the plastic cylinder experimental units (5.5 cm diameter × 9 cm height), i.e., microcosms, and 1 g of A. monspessulanum litter cut into small pieces 1.5 cm length × 0.5 cm width (equivalent dry mass) was evenly distributed on top of the soil surface. At the start of experiment, 1.7 ml of deionized water containing a mixture of yeast and distilled water (10 mg of yeast in 1 ml of deionized water) was added on top of the litter to stimulate microbial growth (Thakur et al., 2017).

Twenty individuals of each collembolan species were added to all microcosm experimental units 7 days after start of the experiment. In order to allow prey acclimation to the leaf litter and soil habitat, 20 individuals of S. scimitus were added 14 days after the start of the experiment. Every two days, the position of all microcosms were randomly rearranged and aerated by opening microcosm lid for 1 min.

The experiment was performed during 8 weeks in climate-controlled rooms (Panasonic ® MLR-352H-PE) with a 16 h: 8 h light: dark photoperiod, a constant temperature and a constant 80% air humidity. The two soil moisture levels were established by adding deionized water on soil at the start of experiment and controlled for the duration of the experiment. The control treatment corresponded to 60% of soil WHC (i.e., natural soil WHC) and the drought treatment by reducing to 50 % the natural WHC of the soil (i.e., 30% of soil WHC) likely close to the worst regional climate models for the Mediterranean Basin predicting a decrease of annual precipitations (from 30 to 45%) for the end of the 21 st century [START_REF] Giorgi | Climate change projections for the Mediterranean region[END_REF][START_REF] Ipcc | Climate change 2013: The physical science basis: working group I contribution to the fifth assessment report of the intergovernmental panel on climate change[END_REF][START_REF] Polade | The key role of dry days in changing regional climate and precipitation regimes[END_REF]Tuel & Eltahir, 2020). This corresponds to 6.0 ml and 3.0 ml of deionized water in 10 g of soil for control and drought treatments, respectively. The two temperature treatments corresponded to a low (15 °C day -12 °C night) and a high (25 °C day -22 °C night) temperature regime. The lowest temperature treatment was based on the temperature at which the four Collembola species were thermally acclimated (i.e., 15 °C) while the highest temperature treatment was established in order to represent a high (+ 10 °C) warming

Accepted Article

This article is protected by copyright. All rights reserved scenario based on regional climatic models [START_REF] Giorgi | Climate change projections for the Mediterranean region[END_REF][START_REF] Ipcc | Climate change 2013: The physical science basis: working group I contribution to the fifth assessment report of the intergovernmental panel on climate change[END_REF][START_REF] Buckley | Temperature extremes: geographic patterns, recent changes, and implications for organismal vulnerabilities[END_REF].

At the end of the experiment, fresh litter and soil from the 64 microcosms were separated and were transferred to Berlese-Tullgren funnels [START_REF] Berlese | Apparecchio per raccogliere presto ed in gran numero piccoli arthropodi[END_REF]. The litter samples were extracted for 1 h and the soil samples were extracted for 7 days. To collect and count remaining individuals, litter was inspected under a stereomicroscope and extracted individuals were stored in 70 % ethanol before counting and identification under a binocular microscope.

Statistical analysis

Statistical analyses were performed using a combination of univariate techniques with R software (version 3.5.1). Significance was evaluated in all cases at P < 0.05.

A generalized linear model (GLZ) with glm function and MASS R package [START_REF] Ripley | Linking species, traits and habitat characteristics of Collembola at European scale[END_REF], followed by post-hoc multiple comparisons (Tukey contrasts) with the glht function and the multcomp R package [START_REF] Hothorn | multcomp: Simultaneous inference in general parametric models[END_REF], were used to test i) for the effects of soil moisture, temperature, predation and their interactions on the abundances of the entire Collembola population and on the 4 Collembola species separately, and ii) for the effects of soil moisture, temperature and their interactions on the predator abundance. Since response variables were count data per microcosm, we performed GLZ models with negative binomial (log link function) error distribution due to overdispersion.

Results

Overall Collembola community response

We collected a total of 55,095 collembolan individuals from all the microcosms with an average of 889 individuals per microcosm after 2 months (Table S2). Total collembolan abundance was 79% lower with the low compared to the high soil moisture condition (Table 1) and 48% lower in presence of the predator (Table 1 and Figure 1a). The impact of predation on total collembolan abundance was also dependent on soil moisture and temperature conditions (significant soil moisture × temperature × predation interaction, Table 1), since the abundance reduction due to predation was amplified under low compared to high soil moisture condition (Figure 1a), and especially in combination with a high temperature (-90%). The effect of temperature treatment on total collembolan abundance was dependent on both soil moisture and predation conditions (Table 1), since total collembolan abundance was

Accepted Article

This article is protected by copyright. All rights reserved 49% higher at 25 °C compared to 15 °C only under high soil moisture condition in presence or absence of a predator, but 37% lower under low moisture condition in predator presence (Figure 1a).

Species-specific Collembola response

Relative proportions of F. candida, P. fimata, P. minuta and M. macrochaeta were respectively 77%, 4%, 18% and 0.4% across all treatments. The abundances of only two Collembola species were negatively affected by the decrease of soil moisture (F. candida and P. minuta), while all species abundances were differently affected by increasing temperature (except M. macrochaeta) and reduced by predator presence (Table 1). However, several interactions between the three treatments were observed (Table 1).

The abundance of F. candida was reduced by 89% under low compared to high soil moisture condition (Table 1 andFigure 1b), while the abundance of P. minuta was reduced at low soil moisture condition except at 25 °C in predator absence (significant soil moisture × temperature × predation interaction, Table 1 and Figure 1c).

The temperature effect on F. candida abundance was dependent on both soil moisture and predation conditions (significant soil moisture × temperature × predation interaction, Table 1) since F. candida abundance was higher at 25 °C compared to 15 °C expect at low moisture condition in predator presence (Figure 1b). The abundance of P. minuta was 81% lower at 25 °C compared to 15 °C only at high soil moisture condition in predator absence (significant soil moisture × temperature × predation interaction, Table 1 and Figure 1c). In absence of predator, increasing temperature positively affected the abundance of M. macrochaeta (+51%) (significant predation × temperature interaction, Table 1; Figure 2a) and inversely reduced by 63% P. fimata abundance (Figure 2b).

The impact of predation on F. candida and P. minuta depended on both soil moisture and temperature conditions (significant soil moisture × temperature × predation interaction, Table 1), since we reported no predation impact on F. candida abundance at low soil moisture combined to low temperature and, in the opposite, no predation impact on P. minuta abundance at high soil moisture combined to high temperature conditions. However, when significant, the predation impact on both F. candida and P. minuta abundances was higher under low compared to high soil moisture conditions (Figure 1b andc). Furthermore, the significant interaction between temperature and predation treatments on P. fimata and M. macrochaeta indicated that the negative effect of predation was amplified by increasing temperature (Table 1; Figure 2a andb).

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Predator response

The abundance of S. scimitus was 22% lower at 25 °C compared to 15 °C (Chisquared = 10.4, P < 0.001; Table S2) but was not affected by the soil moisture treatment (Chi-squared = 1.0, P > 0.05; Table S2).

Discussion

The present experiment focused on the interactive effects of climate change (increasing air temperature and decreasing soil moisture) and predatory control on the abundance of four co-existing Collembola species. We evidenced that altered climatic conditions modify the collembolan community composition with species-specific responses.

In addition, our findings highlight that soil moisture is a major driver of the collembolan community by suppressing the positive effect of increasing temperature and strengthened the predatory control of collembolan abundance.

Climatic change alters Collembola community

Despite a strong research interest in predicting the effects of climate change on Collembola (e.g., Thakur & Eisenhauer, 2015;[START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF][START_REF] Aupic-Samain | Tree litter identity and predator density control prey and predator demographic parameters in a Mediterranean litter-based multi-trophic system[END_REF], only few studies have focused on communities including more than one or two Collembola species especially due to the difficulties in maintaining permanent laboratory cultures of field collected collembolans. In order to reflect the complexity of natural communities, we used 4 distinct Collembola species often used in microcosm studies (e.g., [START_REF] Cortet | Increasing species and trophic diversity of mesofauna affects fungal biomass, mesofauna community structure and organic matter decomposition processes[END_REF][START_REF] Cole | Soil animals influence microbial abundance, but not plant-microbial competition for soil organic nitrogen[END_REF][START_REF] Fountain | Folsomia candida (Collembola): a "standard" soil arthropod[END_REF][START_REF] Park | Effect of laboratory culture conditions on population growth of Proisotoma minuta (Tullberg) (Collembola: Isotomidae)[END_REF]Thakur et al., 2017), which responded differently to dryer and warmer conditions in the present study.

According to our first hypothesis, decreasing soil moisture strongly reduced total collembolan abundances. This finding is in agreement with previous field studies reporting a decrease in abundances with decreasing soil moisture for Collembola (Tsiafouli et al., 2005;[START_REF] Lindo | Traits explain community disassembly and trophic contraction following experimental environmental change[END_REF][START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF]. It is well known that drought may impact Collembola negatively by altering their behaviour (Verhoef & van Selm, 1983;[START_REF] Hågvar | Collembola in Norwegian coniferous forest soils. II. Vertical distribution[END_REF] and physiological processes [START_REF] Hågvar | Collembola in Norwegian coniferous forest soils. II. Vertical distribution[END_REF][START_REF] Poinsot-Balaguer | L'anhydrobiose: un problème biologique nouveau chez les Collemboles (Insecta)[END_REF][START_REF] Holmstrup | Dehydration tolerance and water vapour absorption in two species of soil-dwelling Collembola by accumulation of sugars and polyols[END_REF][START_REF] Gundersen | Surface structure and wetting characteristics of Collembola cuticles[END_REF] leading to higher mortality and/or lower fecundity rates. In addition, we confirmed our second hypothesis of a positive effect of increasing temperature on a collembolan community.

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This article is protected by copyright. All rights reserved However, this positive effect depended on soil moisture conditions since the abundance increased with increasing temperature only at the highest soil moisture condition, consistent with our second hypothesis. As ectothermic organisms, Collembola [START_REF] Gillooly | Effects of size and temperature on metabolic rate[END_REF][START_REF] Rall | Temperature, predator-prey interaction strength and population stability[END_REF] can increase their activities (e.g., feeding, reproduction and growth rates) with increasing temperature but only, as we have demonstrated, when soil moisture conditions are not limiting, leading to increased total collembolan abundance. This finding confirms results from previous field experiments that reported an increase in collembolan abundance with increasing temperature only under wet soil conditions [START_REF] Pflug | Influence of drought and litter age on Collembola communities[END_REF]Xu et al., 2012). However, we acknowledge that twothirds of the total Collembola abundance response to climatic parameters was mainly driven by F. candida, which is often a dominant species under laboratory conditions, suggesting caution to an extrapolation at field community level and necessitating additional experimentations to comfort our findings.

Interestingly, we provided clear evidence of species-specific responses to both decreasing soil moisture and increasing air temperature within the collembolan community.

For instance, decreasing soil moisture reduced the abundances of F. candida and P. minuta (only at low temperature), suggesting a greater drought vulnerability of Isotomidae species compared to Tulbergiidae species. Some collembolans, as reported for the Protaphorura genus, could benefit of processes allowing to prevent water loss in soil [START_REF] Holmstrup | Protaphorura tricampata, a euedaphic and highly permeable springtail that can sustain activity by osmoregulation during extreme drought[END_REF]Holmstrup & Slotsbo, 2018) which could explain that P. fimata was not affected by decreasing soil moisture. Also, P. fimata and M. macrochaeta are eu-edaphic species which may avoid drought period better than hemi-edaphic species by living in deeper and more moist soil layers [START_REF] Hågvar | Collembola in Norwegian coniferous forest soils. II. Vertical distribution[END_REF]. Moreover, M. macrochaeta is known to be a tolerant species to unstable environmental by shifting in reproductive strategies (e.g., sexual and parthenogenesis reproduction under stress and unstressed environmental conditions, respectively; [START_REF] Niklasson | Environmental stress and reproductive mode in Mesaphorura macrochaeta (Tullbergiinae, Collembola)[END_REF], which could likely mitigate negative effect of decreasing moisture. An additional explanation lies in the fact that M. macrochaeta is usually recognized as an early colonizer species [START_REF] Dunger | Changes in collembolan species composition in Eastern German mine sites over fifty years of primary succession[END_REF] and, with small body size associated with a better dispersal ability, could likely migrate to sheltered microsites against desiccating conditions. Consistent with previous field experiments, increasing temperature led to a shift in community composition (e.g., [START_REF] Pflug | Collembola communities along a European transect[END_REF][START_REF] Lindberg | Soil fauna and global change-responses to experimental drought, irrigation, fertilisation and soil warming[END_REF][START_REF] Jucevica | Long-Term Effects of Climate Warming on Forest Soil Collembola[END_REF][START_REF] Petersen | Collembolan communities in shrublands along climatic gradients in Europe and the effect of experimental warming and drought on population density, biomass and diversity[END_REF][START_REF] Daghighi | Long-term succession of Collembola communities in relation to climate change and vegetation[END_REF] highlighting a Collembola sensitivity to warmer conditions with species-specific responses: two species were favored (F. candida and M. macrochaeta)

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This article is protected by copyright. All rights reserved and, oppositely, the two other species were disfavoured (P. fimata and P. minuta only under optimal soil moisture conditions). These findings could be in line with some previous studies that reported a better hatching success for F. candida at 24 °C (89%) compared to 16 °C (52%) [START_REF] Marshall | Preliminary observations on the biology of Folsomia candida Willem, 1902 (Collembola: Isotomidae)[END_REF], a decline of a P. minuta population when the temperature exceeded 20 °C (Thakur et al., 2017) and an increase of M. macrochaeta abundance according to a temperature gradient from 10 °C to 23 °C (Menezes-Oliveira, Scott-Fordsmand, Soares & Amorim, 2014).

Climatic change alters predatory control of the collembolan community

Predator-prey interactions are a key structuring force in population dynamics (Thakur et al., 2017;[START_REF] Laws | Climate change effects on predator-prey interactions[END_REF] and understanding the effects of climate change on these interactions is of primary importance to predict field soil ecosystem responses. As expected, total collembolan abundance was halved with the presence of a gamasid predator. However, shifts in climatic parameters modified the intensity of predation impact on the collembolans and the presence of the predator also altered the response of the collembolan community to changes in climatic parameters. The predation impact on the collembolan community was strengthened with decreasing soil moisture. Indeed, the reduction of total Collembola, F. candida and P. minuta abundances due to predation was amplified under 30% soil WHC compared to 60% soil WHC condition, and especially in combination with the highest temperature. Moreover, the abundance of the predator was not affected by decreasing soil moisture in our experiment, which shows that gamasid predators are less vulnerable to desiccation than their collembolan prey. Thus, our laboratory results provide support to some previous field studies that reported an increase in predation pressure with decreasing precipitation in semiarid grassland [START_REF] Lindberg | Effects of experimental irrigation and drought on the composition and diversity of soil fauna in a coniferous stand[END_REF][START_REF] Kardol | Climate change effects on soil microarthropod abundance and community structure[END_REF] and in Mediterranean forest [START_REF] Santonja | Plant litter mixture partly mitigates the negative effects of extended drought on soil biota and litter decomposition in a Mediterranean oak forest[END_REF].

The positive effect of increasing temperature on M. macrochaeta abundance was suppressed when introducing a predator into the community. Moreover, we observed an increase of predation impact on the abundances of the three other collembolan species with increasing temperature, that was amplified in combination with decreasing soil moisture for F. candida and P. minuta. In line with these findings, Thakur et al., (2017)

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This article is protected by copyright. All rights reserved [START_REF] Santonja | Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola[END_REF] observed also a stronger top-down control by a predatory centipede on F. candida at 20 °C and 25 °C compared to 15 °C. Combining these results suggests increased feeding activity of predatory Acari due to a higher feeding requirement with increasing temperature, but also a higher mobility and thus higher encounter probability between predators and preys leading to reduced prey abundance [START_REF] Rall | Temperature, predator-prey interaction strength and population stability[END_REF].

Conclusion

In the present study, we provided evidence, for the first time, that climate changesimulated and predatory control effects on a complex soil arthropod community constructed by four co-existing Collembola species and a predatory Acari. We highlighted that soil moisture is a major driver of Collembola community structure. Decreasing soil moisture i) reduced total Collembola abundance, ii) suppressed the positive effect of increasing temperature and iii) strengthened the predatory control of the Collembola community especially in combination with a high temperature. The implications of our findings could be important in a climate change context as reduced soil moisture should decrease Collembola abundance and diversity involving a reduced microbial community control (e.g., grazing, dissemination) as well as a reduced prey availability for predators. Consequently, these shifts in Collembola community might have substantial consequences on the whole soil food web and on key ecosystem processes they drive (e.g., litter decomposition and nutrient cycling), especially in Mediterranean ecosystems where biological processes are already strongly limited by water availability [START_REF] Houérou | The isoclimatic mediterranean biomes: bioclimatology, diversity and phytogeography (Doctoral dissertation)[END_REF]. Finally, our results are highly important since they promote the need to studying more complex systems considering distinct soildwelling species, their functional traits and their trophic interactions to better predict the ecosystem responses to the ongoing climate change. Table 1. Chi-square significance of the experimental factors and their interaction produced by the generalized linear model. The factors are soil moisture (60% WHC and 30% WHC), temperature (15 °C and 25 °C), predation (no predator and predator presence) and their effects on collembolan abundances (total Collembola, F. candida, P. fimata, P. minuta and M. macrochaeta). Chi-square (χ 2 ) and associated P-values (with the respective symbols * for P < 0.05, ** for P < 0.01, and *** for P < 0.001) are indicated.

Tables

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No predator Predator

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Figure legends Figure 1 .

 legends1 Figure legends

Figure 2 .

 2 Figure 2. Effects of temperature × predation interaction on (a) M. macrochaeta and (b) P. fimata abundances. Values are means ± SE; n = 16. Different letters denote significant differences between treatments with a < b < c.

  Figure 1.

  reported higher predation effects of the two gamasid predators, H. miles (S. scimitus) and H. aculeifer, on F. candida and P. minuta at intermediate (17-20 °C) and high (22-25 °C) temperatures compared to a low temperature treatment (12-15 °C) in a 60-day microcosm experiment.

We specially thank to Sylvie Dupouyet and Jean-Philippe Orts and Adoudé Adotevi for their technical assistance during the laboratory experiment. Funding was provided by AnaEE France for the O 3 HP facilities, the French Agence Nationale pour la Recherche (ANR) through the project SecPriMe2 (no. ANR-12-BSV7-0016-01), and the program BioDivMeX (BioDiversity of the Mediterranean eXperiment) of the meta-program MISTRALS (Mediterranean Integrated STudies at Regional And Local Scales). This research is also a contribution to the Labex OT-Med (no ANR-11-LABX-0061) funded by the "Investissements d'Avenir" program of the French

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National Research Agency through the A*MIDEX project (no ANR-11-IDEX-0001-02). Finally, the authors declare no conflict of interest. conceived the ideas and designed methodology. AAS, ND and MS collected

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This article is protected by copyright. All rights reserved terrestrial ecosystems. University of California Press. Thakur, M. P., & Eisenhauer, N. (2015). Plant community composition determines the strength of top-down control in a soil food web motif. Scientific Reports, 5, 9134. doi: 10.1038/srep09134 Thakur, M. P, Herrmann, M., Steinauer, K., Rennoch, S., Cesarz, S., & Eisenhauer, N. (2015). Cascading effects of belowground predators on plant communities are densitydependent. Ecology and Evolution, 5(19), 4300-4314. doi: 10.1002/ece3.1597 Thakur, M. P., Künne, T., Griffin, J. N., & Eisenhauer, N. (2017). Warming magnifies predation and reduces prey coexistence in a model litter arthropod system. Proceedings of the Royal Society B: Biological Sciences. Retrieved from https://royalsocietypublishing.org/doi/abs/10.1098/rspb.2016.2570 Thibaud, J. M. (2017). Catalogue des collemboles de France. Zoosystema, 39(3), 297-437. doi: 10.5252/z2017n3a1 Trevors, J. T. (1996). Sterilization and inhibition of microbial activity in soil. Journal of Microbiological Methods, 26(1), 53-59. doi: 10.1016/0167-7012(96)00843-3 Tsiafouli, M. A., Kallimanis, A. S., Katana, E., Stamou, G. P., & Sgardelis, S. P. (2005). Responses of soil microarthropods to experimental short-term manipulations of soil moisture. Applied Soil Ecology, 29(1), 17-26. doi: 10.1016/j.apsoil.2004.10.002 Tuel, A., & Eltahir, E. A. B. (2020). Why is the Mediterranean a climate change hot spot? Journal of Climate, 33(14), 5829-5843. doi: 10.1175/JCLI-D-19-0910.1 Tylianakis, J. M., Didham, R. K., Bascompte, J., & Wardle, D. A. (2008). Global change and species interactions in terrestrial ecosystems. Ecology Letters, 11(12), 1351-1363. doi: 10.1111/j.1461-0248.2008.01250.x Van der Putten, W. H., Macel, M., & Visser, M. E. (2010). Predicting species distribution and abundance responses to climate change: why it is essential to include biotic interactions across trophic levels. Philosophical Transactions of the Royal Society B: Biological Sciences, 365(1549), 2025-2034. Van der Putten, W. H., Vet, L. E. M., Harvey, J. A., & Wäckers, F. L. (2001). Linking aboveand belowground multitrophic interactions of plants, herbivores, pathogens, and their antagonists. Trends in Ecology & Evolution, 16(10), 547-554. doi: 10.1016/S0169-5347(01)02265-0 Verhoef, H. A., & van Selm, A. J. (1983). Distribution and population dynamics of Collembola in relation to soil moisture. Ecography, 6(4), 387-388. doi: 10.1111/j.1600-0587.1983.tb01234.x

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This article is protected by copyright. All rights reserved Violle, C., Navas, M.-L., Vile, D., Kazakou, E., Fortunel, C., Hummel, I., & Garnier, E. (2007). Let the concept of trait be functional ! Oikos, 116(5), 882-892. doi: 10.1111/j.0030-1299[START_REF] Park | Effect of laboratory culture conditions on population growth of Proisotoma minuta (Tullberg) (Collembola: Isotomidae)[END_REF].15559.x Vucic-Pestic, O., Birkhofer, K., Rall, B. C., Scheu, S., & Brose, U. (2010). Habitat structure and prey aggregation determine the functional response in a soil predator-prey interaction. Pedobiologia, 53( 5