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

Amphibians forgo aquatic life in response to alien fish introduction

Species with complex life cycles are good models to understand trade-offs between life in hostile and favourable habitats. Newts remain in breeding wetlands for a long period and are strongly affected by fish introduction; however, mechanisms of the exclusion observed in the field are still not well known. In particular, whether newts skip breeding and leave water for land in response to fish introduction and how aquatic shelter may influence their choice remain open questions. To investigate these questions, we experimentally studied the use of aquatic and terrestrial habitats during the breeding season of palmate newts, Lissotriton helveticus, in the presence and absence of goldfish, Carassius auratus. We determined the consequences of habitat choice on newt fitness by assessing sexual activity and number of eggs. There was a strong, significant avoidance of the aquatic environment in the presence of fish, particularly when no aquatic shelter was available. This escape from the water had an impact on reproduction: newts decreased their sexual activity and laid fewer eggs. The availability of shelters favoured coexistence but did not prevent a large proportion of the newts from leaving water and skipping reproduction. This study shows how the presence of fish and the absence of aquatic shelters can lead to newts forgoing aquatic life, thus improving our understanding of the mechanisms behind the coexistence and exclusion patterns found in the wild. More broadly, these data contribute to explaining aquatic versus terrestrial life in favourable and unfavourable environments

Importance de la connectivité du paysage pour évaluer l’impact du réchauffement climatique sur les tritons

peer reviewedContexte Dans le contexte du réchauffement climatique, la fragmentation du paysage peut à la fois impacter la dispersion des espèces vers des microclimats servant de zone refuge, mais aussi mener à des modifications dans la composition phénotypique des populations. Méthode Nous avons utilisé une approche expérimentale en milieu semi-naturel pour évaluer si l’effet d’une augmentation de 2°C sur l’abondance et la réponse phénotypique de populations de tritons palmés est influencé par la connectivité entre microclimats. Résultats Un climat plus chaud impacte négativement l’abondance des tritons adultes, altère la composition phénotypique des populations et influence la décision d’émigration des juvéniles. Cependant la connectivité entre les habitats thermiques annule ou inverse ces effets. Conclusion La conservation de zones microclimatiques et le maintien de la connectivité paysagère devraient être une préoccupation majeure pour réduire l’impact du réchauffement climatique sur les amphibiens

High Temperatures Limit Developmental Resilience to High-Elevation Hypoxia in the Snake \u3ci\u3eNatrix maura\u3c/i\u3e (Squamata: Colubridae)

Climate change is generating range shifts in many organisms, notably along the altitudinal gradient. However, moving up in altitude exposes organisms to lower oxygen availability, which may negatively affect development and fitness, especially at high temperatures. To test this possibility in a potentially upward-colonizing species, we artificially incubated developing embryos of the viperine snake Natrix maura Linnaeus 1758, using a split-clutch design, in conditions of extreme high elevation or low elevation at two ecologically-relevant incubation temperatures (24 and 32 °C). Embryos at low and extreme high elevations incubated at cool temperatures did not differ in development time, hatchling phenotype or locomotor performance. However, at the warmer incubation temperature and at extreme high elevation, hatching success was reduced. Further, embryonic heart rates were lower, incubation duration longer and juveniles born smaller. Nonetheless, snakes in this treatment were faster swimmers than siblings in other treatment groups, suggesting a developmental trade-off between size and performance. Constraints on development may be offset by the maintenance of important performance metrics, thus suggesting that early life-history stages will not prevent the successful colonization of high-elevation habitat even under the dual limitations of reduced oxygen and increased temperature

Podarcis muralis (Common Wall Lizard). Tail bifurcation

International audienceBrattstrom 1965, op. cit.). The T p from the laboratory gradient for P. lynxe (27.53°C) is at the lower end of previously reported T p for North American Plestiodon (range 28-32.6°C; Fitch 1954, op. cit.; Andrews 1994, op. cit.; Youssef et al. 2008, op. cit.). The significant relationships between T b and environmental temperatures in our study are consistent with other studies on Plestiodon that have found similar significant relationships, especially with T s (Mount 1963, op. cit.; Andrews 1994, op. cit.; Du et al. 2006, op. cit.). Even though there was a statistically significant difference in T b and T p , with T b being higher, the difference was only 0.5°C on average, suggesting T b and T p are fairly similar in P. lynxe. This is consistent with a lack of difference in T b and T p observed in P. laticeps (Pentecost 1974, op. cit.). Taken together, our observations on the thermal ecology of P. lynxe, the most southern species of American Plestiodon to be examined to date, suggests that it is not much different from the other American Plestiodon species for which data are available. Thus, it appears that there may be conservation of thermal ecology within this genus, as suggested by Youssef et al. (2008, op. cit.). This research conformed with all laws and regulations in place in Mexico at the time the research was conducted

Body Size Increases with Elevation in Pyrenean Newts (Calotriton asper)

International audiencePhenotypic variation along environmental gradients—particularly in body size—occurs in a variety of species. Larger-bodied individuals are usually found in colder climates, as predicted by Bergmann's rule. In ectotherms, this pattern remains controversial. Among thermoconformers, smaller body sizes are expected in colder climates because these species might have relatively shorter warm-up times (advantageous in cold climates), whereas the reverse pattern can be expected in thermoregulators (heat-balance hypothesis). In amphibians, additional factors like humidity and thermal niche might also contribute to body-size variation. Following Allen's rule, there can also be a negative relationship between temperature and relative limb length. Here, we described associations among temperature, precipitation, body size, and relative limb length in Calotriton asper. We expected individuals from higher elevations (colder climates) to be smaller when compared to lowelevation conspecifics. We found an influence of temperature on body-size variation but, contrary to expectations, salamanders from colder climates were larger compared to low-elevation populations, which corroborates with the heat-balance hypothesis. In accordance with the converse water-availability hypothesis, we also demonstrated that precipitation was related to body-size variation in this species. Finally, our results supported the predictions of Allen's rule. This trend could be the result of evolutionary responses to harsh environments, driven by either local adaptation, plasticity processes, or a combination of both

Variation of preferred body temperatures along an altitudinal gradient: A multi-species study

International audienceTemperature affects the physiological functions of ectotherms. To maintain optimal body temperature and ensure physiological performance, these organisms can use behavioral adjustments to keep the body temperature in their specific temperature range, so-called preferred temperature (Tpref). It is therefore crucial to describe and understand how Tpref vary within and amongst populations to predict the effects of climate change of altitudinal range shifts in organisms. We aimed at determining the altitudinal variations in Tpref in three ectothermic species (the Pyrenean brook salamander – a semi-aquatic and thigmothermic amphibian – the European common lizard and the wall lizard – both heliothermic species). Using an experimental approach where Tpref were measured along a temperature gradient in laboratory conditions, we used a cross-sectional approach to compare the variation of Tpref measured in populations sampled along the altitudinal gradient in the Pyrenees. We hypothesized a complex and highly variable intra-specific response of Tpref along geographical clines, with a positive relationship between Tpref and altitude (as predicted by the countergradient variation), the reverse pattern (referring to the adaptation of local optima hypothesis), or no relationship at all. Our results corroborated partially the countergradient hypothesis in the salamander (middle to high elevation part). At high altitude level, individuals may compensate for lower opportunities of favorable conditions by choosing a high temperature which maximizes their activities. However, populations from low elevation level hence better supported the adaptation of local optima hypothesis, such as both lizard species, for which Tpref tended instead to decrease with altitude. Lizards from cold climates may be physiologically adapted to low temperature, with the ability to reach optimal functioning at lower temperature than individuals from low altitude. Our findings suggest that predicting future niche models should therefore take into account the variability of Tpref, where species might be differently affected by global warming