Effets de facteurs internes (traits d'histoire de vie et sexe) et externes (qualité d'habitat et densité de population) sur la dispersion et mise en évidence de syndromes de dispersion

La dispersion, définie comme un mouvement individuel pouvant induire des flux de gènes, est un processus crucial pour le maintien à long terme des (méta-)populations. L'apport de nouveaux gènes dans une population permet de contrecarrer l'effet négatif de la dérive génétique et ainsi de limiter les risques de consanguinité, pouvant être néfastes pour les individus et engendrer une extinction des populations. Cette thèse a pour objectif principal d'améliorer notre connaissance sur la dispersion et sur le fonctionnement des populations. Dans un premier temps, des relations entre ce comportement, pouvant être différent d'un sexe à l'autre (dispersion biaisée par le sexe) et des traits d'histoire de vie ont été mises en évidence chez les amphibiens et les papillons, permettant dans un deuxième temps de prédire à partir de quelques traits les capacités de dispersion chez les espèces pour lesquelles les données de dispersion restent manquantes. Certains traits d'histoire de vie ont également montré des coévolutions avec la dispersion biaisée par le sexe. En parallèle de ces traits internes, l'influence de la qualité d'habitat, de la densité de population ainsi que du sexe ratio a également été étudié sur la dispersion de la piéride du chou (Pieris brassicae) en milieu expérimental (le Métatron). Tous les résultats de ce travail soulignent la complexité des pressions - internes, environnementales ou populationnellles - agissant sur la dispersion des individus (impact différent en fonction des sexes), et permettent de mieux comprendre les processus responsables de ce comportement nécessaire au maintien à long terme des populations.Dispersal, defined as an individual movement can induce gene flow, is a key process for metapopulations persistence. The addition of new genes in a population can counteract the negative effects of the genetic drift and thus reduce the risk of inbreeding, increasing the extinction rate of populations. The main objective of this thesis was to improve our understanding about the factors inducing dispersal and about the metapopulations functioning. At first, the relationship between this behavior - may be different from one sex to the other (sex-biased dispersal) - and life history traits have been identified in amphibians and butterflies. These relationships were then used to predict dispersal abilities among species for which data about dispersal are still missing. Some life history traits also showed coevolutions with sex-biased dispersal. Adding to these internal factors, the influence of habitat quality, population density and sex ratio were also studied on the dispersal of the cabbage butterfly (Pieris brassicae) in experimental condition (the Metatron). All results of this study highlight the complexity of pressures - internal, environmental or populationnal - acting on the dispersal of individuals (different impact by gender), and improve our understanding about the metapopulations functioning

Influence of substrate types and morphological traits on movement behavior in a toad and newt species

Background Inter-patch movements may lead to genetic mixing, decreasing both inbreeding and population extinction risks, and is hence a crucial aspect of amphibian meta-population dynamics. Traveling through heterogeneous landscapes might be particularly risky for amphibians. Understanding how these species perceive their environment and how they move in heterogeneous habitats is an essential step in explaining metapopulation dynamics and can be important for predicting species’ responses to climate change and for conservation policy and management. Methods Using an experimental approach, the present study focused on the movement behavior (crossing speed and number of stops) on different substrates mimicking landscape components (human-made and natural substrates) in two amphibian species contrasting in locomotion mode: the common toad (Bufo bufo), a hopping and burrowing anuran and the marbled newt (Triturus marmoratus), a walking salamander. We tested the hypothesis that species reaction to substrate is dependent on specific ecological requirements or locomotion modes because of morphological and behavioral differences. Results In both species, substrate type influenced individual crossing speed, with individuals moving faster on soil than on concrete substrate. We also demonstrated that long-legged individuals moved faster than individuals with short legs. In both species, the number of stops was higher in females than in males. In common toads, the number of stops did not vary between substrates tested, whereas in marbled newts the number of stops was higher on concrete than on soil substrate. Discussion We highlighted that concrete substrate (mimicking roads) negatively affect the crossing speed of both studied species, with an effect potentially higher in marbled newts. Our findings corroborate negative effects of such heterogeneous landscapes on movement behavior of two amphibian species, which may have implications for the dynamics of metapopulations

Marking techniques in the Marbled Newt (<em>Triturus marmoratus</em>): PIT-Tag and tracking device implant protocols

Individual marking has become essential for studying population dynamics and ecological requirements. However, marking small-bodied species such as amphibians is becoming a challenge in the last decades. Amphibian surveys may require to mark manually individuals, using toe clipping, polymers and pigments, or passive integrated transponders (PIT-tags). Even if ethics committees have recently recommend avoiding toe clipping in amphibians, the use of PIT-tags led to controversial results because low tag retention reported in some studies. Here, we describe a protocol of potentially life-long PIT-tag marking in a protected species, the marbled newt Triturus marmoratus. In addition, we also detailed a second procedure of surgery for the implantation of transmitters needed in radio-tracking surveys. During both procedures, we found that the newt phase (either aquatic or terrestrial) strongly affected the anesthesia duration. Indeed, newts in aquatic phase were more quickly anesthetized than newts under terrestrial phase. We then recommend to pay attention of this physiological particularity when performing this kind of procedure. Improving our knowledge on ecological requirements and population dynamics of this species is crucial for management and conservation plans, and could be extended to other large newts

Marking techniques in the Marbled Newt (Triturus marmoratus): PIT-Tag and tracking device implant protocols

Individual marking has become essential for studying population dynamics and ecological requirements. However, marking small-bodied species such as amphibians is becoming a challenge in the last decades. Amphibian surveys may require to mark manually individuals, using toe clipping, polymers and pigments, or passive integrated transponders (PIT-tags). Even if ethics committees have recently recommend avoiding toe clipping in amphibians, the use of PIT-tags led to controversial results because low tag retention reported in some studies. Here, we describe a protocol of potentially life-long PIT-tag marking in a protected species, the marbled newt Triturus marmoratus. In addition, we also detailed a second procedure of surgery for the implantation of transmitters needed in radio-tracking surveys. During both procedures, we found that the newt phase (either aquatic or terrestrial) strongly affected the anesthesia duration. Indeed, newts in aquatic phase were more quickly anesthetized than newts under terrestrial phase. We then recommend to pay attention of this physiological particularity when performing this kind of procedure. Improving our knowledge on ecological requirements and population dynamics of this species is crucial for management and conservation plans, and could be extended to other large newts

Multiple glacial refugia and contemporary dispersal shape the genetic structure of an endemic amphibian from the Pyrenees

Historical factors (colonization scenarios, demographic oscillations) and contemporary processes (population connectivity, current population size) largely contribute to shaping species’ present-day genetic diversity and structure. In this study, we use a combination of mitochondrial and nuclear DNA markers to understand the role of Quaternary climatic oscillations and present-day gene flow dynamics in determining the genetic diversity and structure of the newt Calotriton asper (Al. Dugès, 1852), endemic to the Pyrenees. Mitochondrial DNA did not show a clear phylogeographic pattern and presented low levels of variation. In contrast, microsatellites revealed five major genetic lineages with admixture patterns at their boundaries. Approximate Bayesian computation analyses and linear models indicated that the five lineages likely underwent separate evolutionary histories and can be tracked back to distinct glacial refugia. Lineage differentiation started around the Last Glacial Maximum at three focal areas (western, central and eastern Pyrenees) and extended through the end of the Last Glacial Period in the central Pyrenees, where it led to the formation of two more lineages. Our data revealed no evidence of recent dispersal between lineages, whereas borders likely represent zones of secondary contact following expansion from multiple refugia. Finally, we did not find genetic evidence of sex-biased dispersal. This work highlights the importance of integrating past evolutionary processes and present-day gene flow and dispersal dynamics, together with multilocus approaches, to gain insights into what shaped the current genetic attributes of amphibians living in montane habitats.info:eu-repo/semantics/publishedVersio

Supplementary material 2 from: Trochet A, Schmeller D (2013) Effectiveness of the Natura 2000 network to cover threatened species. Nature Conservation 4: 35-53. https://doi.org/10.3897/natureconservation.4.3626

Supplementary material 2 from: Trochet A, Schmeller D (2013) Effectiveness of the Natura 2000 network to cover threatened species. Nature Conservation 4: 35-53. https://doi.org/10.3897/natureconservation.4.362

Modeling potential distributions of three European amphibian species comparing ENFA and MaxEnt

International audienceUnderstanding the distribution and habitat preferences of amphibians is crucial to protecting their declining populations. It remains a challenge because most species are difficult to detect, enough data on their occurrence are needed, and the contribution of climatic and habitat factors is not well known. Various modeling approaches exist both to infer habitat preferences based on known locations, and to extrapolate species geographic distributions. We used presence-only data of three anuran species from original naturalist databases covering 34,750 km² in the western part of France, including 660 occurrences for the Common Midwife Toad (Alytes obstetricans), 1,910 for the Spined Toad (Bufo spinosus), and 975 for the Common Brown Frog (Rana temporaria). We compared two current modeling approaches, the Ecological Niche Factor Analysis (ENFA) and Maximum Entropy (MaxEnt) to model their potential distributions by including high resolution climate variables, and habitat and landscape variables. For each species, both analyses allowed a refined understanding of the relationships between habitat factors and the species distribution. We showed that climate and natural grasslands are key factors in explaining the species distributions and that the surrounding environment of aquatic habitats is an important driver of amphibian presence. The two models gave different predictions of distributions, which may lead to different planning of conservation areas. Our study confirms the importance of using and comparing several models, and evidenced the importance of collecting field data at a regional scale

Reduction in the metabolic levels due to phenotypic plasticity in the Pyrenean newt, Calotriton asper, during cave colonization

International audienceAccording to theories on cave adaptation, cave organisms are expected to develop a lower metabolic rate compared to surface organisms as an adaptation to food scarcity in the subterranean environments. To test this hypothesis, we compared the oxygen consumption rates of the surface and subterranean populations of a surface-dwelling species, the newt Calotriton asper, occasionally found in caves. In this study, we designed a new experimental setup in which animals with free movement were monitored for several days in a respirometer. First, we measured the metabolic rates of individuals from the surface and subterranean populations, both maintained for eight years in captivity in a natural cave. We then tested individuals from these populations immediately after they were caught and one year later while being maintained in the cave. We found that the surface individuals that acclimated to the cave significantly reduced their oxygen consumption, whereas individuals from the subterranean population maintained in the cave under a light/dark cycle did not significantly modify their metabolic rates. Second, we compared these metabolic rates to those of an obligate subterranean salamander (Proteus anguinus), a surface aquatic Urodel (Ambystoma mexicanum), and a fish species (Gobio occitaniae) as references for surface organisms from different phyla. As predicted, we found differences between the subterranean and surface species, and the metabolic rates of surface and subterranean C. asper populations were between those of the obligate subterranean and surface species. These results suggest that the plasticity of the metabolism observed in surface C. asper was neither directly due to food availability in our experiments nor the light/dark conditions, but due to static temperatures. Moreover, we suggest that this adjustment of the metabolic level at a temperature close to the thermal optimum may further allow individual species to cope with the food limitations of the subterranean environmen

How is dispersal integrated in life histories: a quantitative analysis using butterflies

As dispersal plays a key role in gene flow among populations, its evolutionary dynamics under environmental changes is particularly important. The inter-dependency of dispersal with other life history traits may constrain dispersal evolution, and lead to the indirect selection of other traits as a by-product of this inter-dependency. Identifying the dispersalÕs relationships to other life-history traits will help to better understand the evolutionary dynamics of dispersal, and the consequences for species persistence and ecosystem functioning under global changes. Dispersal may be linked to other life-history traits as their respective evolutionary dynamics may be interdependent, or, because they are mechanistically related to each other. We identify traits that are predicted to co-vary with dispersal, and investigated the correlations that may constrain dispersal using published information on butterflies. Our quantitative analysis revealed that (1) dispersal directly correlated with demographic traits, mostly fecundity, whereas phylogenetic relationships among species had a negligible influence on this pattern, (2) gene flow and individual movements are correlated with ecological specialisation and body size, respectively and (3) routine movements only affected short-distance dispersal. Together, these results provide important insights into evolutionary dynamics under global environmental changes, and are directly applicable to biodiversity conservation

Data from: Local predation risk and matrix permeability interact to shape movement strategy

In fragmented landscapes, the reduced connectivity among patches drives the evolution of movement strategies through an increase of transience costs. Reduced movements may further alter heterogeneity in biotic and abiotic conditions experienced by individuals. The joint action of local conditions and matrix permeability may shape emigration decisions. Here, we tested the interactive effects of predation risk and matrix permeability on movement propensity, movement costs and movers’ phenotype in the common toad Bufo bufo. In a full-crossed experimental design, we assessed the movement propensity of juveniles in three connectivity treatments (from poorly to highly permeable matrix), with or without predation risk in their living patch. We also assessed the relationships between movement propensity and morphological traits (i.e. body and leg length) and how it affected the movement cost (i.e. mass loss). Movement propensity increased in presence of predation risk, while matrix permeability had no effect. However, matrix permeability interacted with predation risk to influence movers’ phenotype and the physiological cost they endured while moving. In particular, a well-known movement syndrome in toads (i.e. movement propensity positively related to longer legs) depended on the interaction between matrix permeability and predation risk and resulted in differences in mass loss among matrix types. Movers lost more mass on average than residents except when they also displayed longer legs or when they crossed the most permeable matrix in the presence of predation risk. Our results show that matrix permeability shapes the physiological cost of dispersal by changing the identity of individuals moving away from local conditions. As the movers’ phenotype can importantly alter (meta)population dynamics, context-dependency of dispersal syndromes should be considered in studies predicting the functioning of human-altered natural systems