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Identifying ecomorphological convergence examples is a central focus in evolutionary biology. In xenarthrans, slow arboreality independently arose at least three times, in the two genera of ‘tree sloths’,BradypusandCholoepus, and the silky anteater,Cyclopes. This specialized locomotor ecology is expectedly reflected by distinctive morpho-functional convergences.Cyclopes, although sharing several ecological features with ‘tree sloths’, do not fully mirror the latter in their outstandingly similar suspensory slow arboreal locomotion. We hypothesized that the morphology ofCyclopesis closer to ‘tree sloths’ than to anteaters, but yet distinct, entailing that slow arboreal xenarthrans evolved through ‘incomplete’ convergence. In a multivariate trait space, slow arboreal xenarthrans are hence expected to depart from their sister taxa evolving toward the same area, but not showing extensive phenotypical overlap, due to the distinct position ofCyclopes.Conversely, a pattern of ‘complete’ convergence (i.e., widely overlapping morphologies) is hypothesized for ‘tree sloths’. Through phylogenetic comparative methods, we quantified humeral and femoral convergence in slow arboreal xenarthrans, including a sample of extant and extinct non-slow arboreal xenarthrans. Through 3D geometric morphometrics, cross-sectional properties (CSP) and trabecular architecture, we integratively quantified external shape, diaphyseal anatomy and internal epiphyseal structure. Several traits converged in slow arboreal xenarthrans, especially those pertaining to CSP. Phylomorphospaces and quantitative convergence analyses substantiated the expected patterns of ‘incomplete’ and ‘complete’ convergence for slow arboreal xenarthrans and ‘tree sloths’, respectively. This work, highlighting previously unidentified convergence patterns, emphasizes the value of an integrative multi-pronged quantitative approach to cope with complex mechanisms underlying ecomorphological convergence.

In this study, we suggest a method adapted to the retrodeformation of asymmetrical objects – such as limb bones – by quantitatively estimating the effectiveness of the Thin-Plate Splines (TPS) interpolation function as a retrodeformation tool. To do so, taphonomic deformations were first simulated on a single horse femur. The original bone was then used as a reference in order to drive the retrodeformation using anatomical landmarks. This approach, based on a single bone, enabled us to evaluate the performance of the retrodeformation procedure. Then, the same approach was performed on a sample of rhino femora but using a different specimen (from the same species) as the reference in order to account for morphological variation. We also added sliding semi-landmarks on anatomical curves. Finally, retrodeformation was applied on a sample of sauropodomorph dinosaur femora by building a mean shape based on several well-preserved fossil specimens. Results show that entirely flattened and stretched bones are more efficiently retrodeformed than bent and twisted bones. Introduction of morphological variation increased the efficiency of retrodeformation for bent and locally stretched bones. The application to the sample of fossils produced similar results but also highlighted the difficulty of retrodeforming bones with a combination of different deformations. TPS interpolation is an efficient tool of retrodeformation for asymmetrical objects, especially for bones with only one affine deformation such as flattening or stretching. Finding a threshold of landmark number to use for this process would be the next step because it would allow us to ensure the quality of retrodeformation while keeping available a reasonable number of landmarks in order to perform shape analysis on retrodeformed bones. Twisted and bent fossils are frequently discovered and we suggest that these kinds of deformations should be studied with caution, especially when combined with other types of taphonomic distortions.

Sciuromorph rodents are a monophyletic group comprising about 300 species with a body mass range spanning three orders of magnitude and various locomotor behaviors that we categorized into arboreal, fossorial and aerial. The purpose of this study was to investigate how the interplay of locomotor ecology and body mass affects the morphology of the sciuromorph locomotor apparatus. The most proximal skeletal element of the hind limb, i.e. the femur, was selected, because it was shown to reflect a functional signal in various mammalian taxa. We analyzed univariate traits (effective femoral length, various robustness variables and the in‐levers of the muscles attaching to the greater, third and lesser trochanters) as well as femoral shape, representing a multivariate trait. An ordinary least‐squares regression including 177 species was used to test for a significant interaction effect between body mass and locomotor ecology on the variables. Specifically, it tested whether the scaling patterns of the fossorial and aerial groups differ when compared with the arboreal, because the latter was identified as the ancestral sciuromorph condition via stochastic character mapping. We expected aerial species to display the highest trait values for a given body mass as well as the steepest slopes, followed by the arboreal and fossorial species along this order. An Ornstein–Uhlenbeck regression fitted to a phylogenetically pruned dataset of 140 species revealed the phylogenetic inertia to be very low in the univariate traits, hence justifying the utilization of standard regressions. These variables generally scaled close to isometry, suggesting that scaling adjustments might not have played a major role for most of the femoral features. Nevertheless, the low phylogenetic inertia indicates that the observed scaling patterns needed to be maintained during sciuromorph evolution. Significant interaction effects were discovered in the femoral length, the centroid size of the condyles, and the in‐levers of the greater and third trochanters. Additionally, adjustments in various femoral traits reflect the acquisitions of fossorial and aerial behaviors from arboreal ancestors. Using sciuromorphs as a focal clade, our findings exemplify the importance of statistically accounting for potential interaction effects of different environmental factors in studies relating morphology to ecology.

International audience; Phenotypic integration, defined as the coordinated co-variation of parts of an organism can be an important constraint on phenotypic diversification. Functional factors, by having an heterogeneous impact across the animal body, may reinforce the integration of some parts while causing a perturbation of the integration among other parts. The integration across the locomotor apparatus should thus reflect to a certain extent the locomotor ecology of the animal. Using the mustelids as study group, we track changes in the patterns of co-variation in species belonging to four different locomotor ecologies (terrestrial, semi-arboreal, semi-fossorial, and semi-aquatic). Our results highlight the strong overall integration in mustelid long bones. The main shape changes associated with co-variations between skeletal elements are the bone robustness and proportions of the epiphyses. The pattern of co-variation is, however, only slightly impacted by allometry. Changes in co-variation between species mostly scale with phylogenetic divergence time, except for the (Mustela putorius, M. eversmanni, M. lutreola) clade which, despite a short divergence time, presents strong differences in co-variation. Co-variation patterns differ between locomotor ecologies, but few of these variations match the hypothesis of a reduction of integration due to functional specialization. This may reflect our lack of knowledge on the functional modules in species with locomotor ecologies that differ from terrestrial locomotion rather than invalidate our a priori hypotheses.

International audience; Adaptation to an aquatic lifestyle has occurred independently in numerous amniote lineages. Such ecological shifts commonly engender adaptive changes in the musculoskeletal system. Semi-aquatic taxa highlight the compromises needed to enable locomotion both on land and in water and during the initial stages of the transition from land to water. Interestingly, mustelids include some semi-aquatic taxa that are primarily terrestrial and others that are primarily aquatic. Using microtomography, the inner bone structure of the whole stylopod from eight different mustelid taxa with distinct swimming abilities and ecologies was submitted to qualitative and quantitative analysis. Three main patterns in the three-dimensional inner organization of bone were identified, which illustrate three steps in the process of secondary adaptation to an aquatic lifestyle. These include a tubular organization in (primarily) terrestrial forms, a thickening of the cortex and an extension of the trabecular network in most otters, and a strong thickening of the cortex and a much denser and more widespread trabecular network in the almost exclusively aquatic sea otter. Microanatomical data are in agreement with morphological data and highlight consistency between the forearm and hindlimb patterns. The osteosclerotic pattern of the sea otter shows similarities to those of some aquatic amni-otes, but additional comparative three-dimensional microanatomical data are required to elucidate its functional significance. ADDITIONAL KEYWORDS: bone mass increase-long bones-microanatomy-Mustelidae-osteosclerosis-semi-aquatic.

International audience; The shape of long bones is linked to a species' ecology and is thought to reflect the constraints imposed by locomo-tion. The evolution of the shape of the long bones in semi-aquatic mustelids has likely been shaped by the divergent mechanical properties of both water and land. Adaptation to a semi-aquatic lifestyle occurred independently in otters (Lutrinae) and minks (Mustelinae). Here we test the idea that these similar locomotor constraints led to morphological convergence between minks and otters, and between European and American minks. We use 3D geometric morphometrics to quantify shape differences in the humerus, radius, ulna, femur, tibia and fibula of ten species of mustelids belonging to the Lutrinae and Mustelinae subfamilies. Our results show convergence in all bones between the European and American minks, but this convergence is significant only for the humerus. We suggest that this strong convergence in humeral shape between the two minks results from functional demands on the forelimb as it produces most of the thrust when swimming in minks. The American minks show a slight but nonsignificant convergence with the Lutrinae for the shape of the ulna, femur and tibia. The sea otter (Enhydra lutris) shows an ulnar and radial shape that diverges from that observed in the other Lutrinae, possibly due to the strong manipulative abilities and unique locomotor mode of this species. In contrast to our initial hypothesis, bone shape in minks does not converge significantly with that of otters. Otters show a large variety of shapes suggesting that a semi-aquatic lifestyle can comprise a wide array of locomotor behaviours.

International audience; Landscape fragmentation is a major threat to biodiversity. It results in the transformation of continuous (hence large) habitat patches into isolated (hence smaller) patches, embedded in a matrix of another habitat type. Many populations are harmed by fragmentation because remnant patches do not fulfil their ecological and demographic requirements. In turn, this leads to a loss of biodiversity, especially if species have poor dispersal abilities. Moreover, landscape fragmentation is a dynamic process in which patches can be converted from one type of habitat to another. A recently created habitat might suffer from a reduced biodiversity because of the absence of adapted species that need a certain amount of time to colonize the new patch (e.g. direct meta-population effect). Thus landscape dynamics lead to complex habitat spatiotemporal structured, in which each patch is more or less continuous in space and time. In this study, we define habitat spatial structure as the degree to which a habitat is isolated from another habitat of the same kind and temporal structure as the time since the habitat is in place. Patches can also display reduced biodiversity because their spatial or temporal structures are correlated with habitat quality (e.g. indirect effects). We discriminated direct meta-community effects from indirect (habitat quality) effects of the spatiotemporal structure of habitats on biodiversity using Collembola as a model. We tested the relative importance of spatial and temporal structure of habitats for collembolan diversity, taking soil properties into account. In an agroforested landscape, we set up a sampling design comprised of two types of habitats (agriculture versus forest), a gradient of habitat isolation (three isolation classes) and two contrasting ages of habitats. Our results showed that habitat temporal structure is a key factor shaping collembolan diversity. A reduced diversity was detected in recent habitats, especially in forests. Interactions between temporal continuity and habitat quality were also detected by taking into account soil properties: diversity increased with soil carbon content, especially in old forests. Negative effects of habitat age on diversity were stronger in isolated patches. We conclude that habitat temporal structure is a key factor shaping collembolan diversity, while direction and amplitude of its effect depend on land use type and spatial isolation.