Influence of landscape connectivity on newt’s response to a warmer climate

English. peer reviewed

English. Context: Climate change and habitat fragmentation exert considerable pressures on biodiversity. The spatial distribution of microclimatic refuges in the landscape can influence species responses to warming climates. Objectives: Using a semi-natural experiment, we investigated the potential synergetic effects of climate warming and habitat connectivity on a single amphibian species. Methods: We monitored populations of the palmate newt, Lissotriton helveticus, under two climate treatments, a warmer climate (+ ~ 2 °C) or a present-day climate, in mesocosms either isolated or connected to the other climatic conditions. We assessed the abundance and phenotype (snout-vent length, body condition and skin coloration: darkness and redness) of juvenile and adult newts, and the dispersal propensity of juveniles. Results: Over the 4 years of climatic manipulation, populations tended to increase more in the present-day than in the warmer climate. Warmer climates decreased the abundance of adult newts and altered the phenotypic composition of populations with darker and less red newts. However, connectivity between the two climates cancelled out the effect of a warmer climate on abundance and reversed the effects on phenotype composition. We further found that juvenile newts from the present-day climate treatment tended to emigrate more from warmer conditions during our laboratory dispersal assay and that population isolation disrupted a common covariation between emigration propensity and body size, leg length and skin darkness. Conclusions: Our results point to a synergetic effect of climate warming and fragmentation on the demography of newt populations and emigration decisions of juveniles, suggesting that microclimate refuges and their accessibility play a key role in buffering the impacts of climate warming, with potential implications for amphibian diversity at a regional scale.