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Counter-gradient variation in thermoregulation in a widespread chilean lizard
Whether thermoregulation behaviour is evolutionary rigid or in the contrary evolutionary labile has been a long-standing controversy in the field of thermal biology. In squamate reptiles, including terrestrial lizard species, comparative evidence from the literature suggests that some thermal biology traits may vary adaptively across species but only a handful of studies have found significant variation in thermoregulation behaviour among populations within the same species, for example along an altitudinal gradient. In this article, we investigate geographic variation in thermoregulation behaviour between the range margins of the distribution of the widespread Liolaemus pictus lizard in Chile. The genus Liolaemus is highly diversified in South America, with more than 200 recognized species, and its thermal biology has been extensively characterized during the last decade. We compared the thermoregulation behaviour of lizards from two populations located at the warm and one population located at the cold range margin during two years, and manipulated thermal conditions in the laboratory during one year to test if the geographic variation could be due to thermal acclimation. To our surprise, we found that lizards from the cold margin preferred higher body temperatures and were as effective thermoregulators as lizards from the warm margin. We propose that this pattern is caused by "counter-gradient temperature" variation where there is strong selection for a faster life cycle in the less thermally suitable habitats from the cold margin. We compare our results with those published in the literature on Liolaemus lizards and demonstrate that more thermally challenging environments select for a higher thermoregulation effort and a more effective thermoregulation. Altogether, these data confirm that thermoregulation behaviour is evolutionary labile within and between species of Liolaemus lizards. This conclusion will be of wide interest to those interested in thermal biology of lizards and the evolution of thermoregulation behaviours.
Chaiten population



• Variation in thermoregulation behavior between range margins is rarely investigated
• Liolaemus lizards from the cold margin preferred higher body temperatures
• Thermal acclimation may contribute to this counter-gradient temperature variation
• Selection for faster life cycle in a colder environment may explain the geographic variation.

New tools for population viability analyses
 Oenothera glaziovianaSince three decades, the toolbox of biologists to assess conservation status of endangered species and take actions to improve their long-term viability includes the very popular matrix population models. For this range of models where populations are divided into discrete stages, a solid mathematical framework is available (e.g., Caswell Matrix population models 2001). In addition, softwares such as RAMAS or demogR allow to implement these models in real ecological situations. Unfortunately, not all populations of plants and animals can be divided into discrete categories without loss of significant biological information because individuals often differ for continuous traits such as body size, body condition or growth potential. Continuously structured populations can be described using integral projection models (IPMs), a mathematical framework first introduced by Stephen Ellner and collaborators (Easterling et al. Ecology 2000) and now more and more popular among population ecologists (Coulson Oikos 2012). Although the IPM is efficient with small data sets (Ramula et al. Journal of Applied Ecology 2009), it has not yet been used for real life population viability analyses. In this article, we present for the first time population viability analyses of animal and plant species using the stochastic IPM recently developed by Vindenes and collaborators (Ecology 2011). We show how to construct the stochastic IPM, demonstrate how to calculate and decompose deterministic and stochastic components of the population growth rate, and show results of sensitivity analyses. In addition, we compare results of a diffusion approximation with individual based simulations.
Photograph: Populations of Oenothera glazioviana, an evening primrose with a semelparous reproduction and size-structured populations were modelled in this study (photograph by Bernd Sauerwein on Wiki Commons)
Last Updated ( jeudi, 08 décembre 2016 )
Plasticity in breeding phenology is not consistent across populations
Puy Mary population
Recent studies have identified so-called universal ecological consequences of climate warming, especially an advanced breeding and non-breeding phenology in many populations of plants and animals. In seasonal environments, among species variation in the extent of plasticity of phenology can generate temporal mistmatch between trophic level, where for example predators have higher energetic demands when preys are scarce in the environment. Until recently, however, we knew little about intra-specific variation in breeding phenology, which may vary across populations due to differences in selection or constraints. In a recent study, we combined data from more than 10 years of detailed monitoring of the breeding phenology in 11 populations of common lizards across the Massif Central. Our data demonstrate unambiguously that breeding phenology responds more to climate warming in some populations than in others. Contrary to some predictions from evolutionary theory, plasticity was stronger in warmer and less variable climates.
Picture: The Puy Mary population is characterised by cold and less variable climate conditions during gestation. This population is predicted to exhibit flat plasticity of the breeding phenology. Photograph: J.-F. Le Galliard.
Last Updated ( vendredi, 26 février 2016 )