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

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

Presence of the Fungus B. dendrobatidis, but not B. salamandrivorans, in Wild Pyrenean Brook Newts (Calotriton asper) in Spain and France

International audienceIn the last 20 years, the emergence of chytridiomycosis due to the chytrid fungi Batrachochytrium dendrobatidis (Bd), and the more recently described Batrachochytrium salamandrivorans (Bsal), has caused severe amphibian population regressions across the planet (Bosch et al. 2001; Spitzen-van der Sluijs et al. 2016; Scheele et al. 2019). This has generated an increase in scientific interest to decipher the complex interaction between the environment, the fungus and amphibian hosts, and increased surveillance efforts in many localities (Canessa et al. 2020). Batrachochytrium spp. affect the vital function of the amphibian skin, leading to lethargy or skin discoloration, hyperkeratosis, erosions (even ulcerations in Bsal) of the epidermis, and eventually death (Berger et al. 1998; Weldon et al. 2004; Stuart et al. 2004; Wake and Vredenburg 2010; Martel et al. 2013). Bd is currently found on all continents where amphibians are present (Skerratt et al. 2007), affecting more than 700 species within the three orders of amphibians and has been considered a major threat to amphibian biodiversity worldwide (Crawford et al. 2010; Fisher et al. 2012; Olson et al. 2013; Olson and Ronnenberg 2014)

Presence of the Fungus Batrachochytrium dendrobatidis, but not Batrachochytrium salamandrivorans, in Wild Pyrenean Brook Newts (Calotriton asper) in Spain and France

Este artículo contiene 6 páginas, 12 tabla, 2 figuras.This work was supported by the French Laboratory of Excellence project TULIP (ANR-10-LABX-41; ANR-11-IDEX-0002-02) by the INTERREG POCTEFA ECTOPYR (no. EFA031/15) and by the LIFE+ LIMNOPIRINEUS (LIFE13 NAT/ ES1210) projects.Peer reviewe

High temperatures limit developmental resilience to high-elevation hypoxia in the snake Natrix maura (Squamata: Colubridae)

International audienceClimate 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

High‐elevation hypoxia impacts perinatal physiology and performance in a potential montane colonizer

International audienceClimate change is generating range shifts in many organisms, notably along the elevational gradient in mountainous environments. However, moving up in elevation exposes organisms to lower oxygen availability, which may reduce the successful reproduction and development of oviparous organisms. To test this possibility in an upward‐colonizing species, we artificially incubated developing embryos of the viperine snake (Natrix maura) using a split‐clutch design, in conditions of extreme high elevation (hypoxia at 2877 m above sea level; 72% sea‐level equivalent O2 availability) or low elevation (control group; i.e. normoxia at 436 m above sea level). Hatching success did not differ between the two treatments. Embryos developing at extreme high elevation had higher heart rates and hatched earlier, resulting in hatchlings that were smaller in body size and slower swimmers compared to their siblings incubated at lower elevation. Furthermore, post‐hatching reciprocal transplant of juveniles showed that snakes which developed at extreme high elevation, when transferred back to low elevation, did not recover full performance compared to their siblings from the low elevation incubation treatment. These results suggest that incubation at extreme high elevation, including the effects of hypoxia, will not prevent oviparous ectotherms from producing viable young, but may pose significant physiological challenges on developing offspring in ovo. These early‐life performance limitations imposed by extreme high elevation could have negative consequences on adult phenotypes, including on fitness‐related traits

Presence of the Fungus B. dendrobatidis, but not B. salamandrivorans, in Wild Pyrenean Brook Newts (Calotriton asper) in Spain and France

International audienceIn the last 20 years, the emergence of chytridiomycosis due to the chytrid fungi Batrachochytrium dendrobatidis (Bd), and the more recently described Batrachochytrium salamandrivorans (Bsal), has caused severe amphibian population regressions across the planet (Bosch et al. 2001; Spitzen-van der Sluijs et al. 2016; Scheele et al. 2019). This has generated an increase in scientific interest to decipher the complex interaction between the environment, the fungus and amphibian hosts, and increased surveillance efforts in many localities (Canessa et al. 2020). Batrachochytrium spp. affect the vital function of the amphibian skin, leading to lethargy or skin discoloration, hyperkeratosis, erosions (even ulcerations in Bsal) of the epidermis, and eventually death (Berger et al. 1998; Weldon et al. 2004; Stuart et al. 2004; Wake and Vredenburg 2010; Martel et al. 2013). Bd is currently found on all continents where amphibians are present (Skerratt et al. 2007), affecting more than 700 species within the three orders of amphibians and has been considered a major threat to amphibian biodiversity worldwide (Crawford et al. 2010; Fisher et al. 2012; Olson et al. 2013; Olson and Ronnenberg 2014)

Isolation and characterization of fourteen polymorphic microsatellite markers in the viperine snake Natrix maura

International audienceNineteen polymorphic microsatellite loci were identified and developed for Natrix maura. Polymorphism was assessed for 120 individuals sampled across four sampling sites from the French Pyrenees Mountains. The number of alleles per locus ranged from 3 to 15, and expected heterozygosity per locus ranged from 0.227 to 0.863. We tested for deviation from Hardy–Weinberg equilibrium and linkage disequilibrium and assessed the presence of null alleles for all loci, resulting in a selection of 14 high‐quality polymorphic markers. These markers will be extremely useful in identifying fine‐scale genetic structures and providing insight into conservation management plans of this species