The Effects of Habitat Fragmentation on the Thermal Plasticity of the Aegean Wall Lizard (Podarcis Erhardii, Lacertidae)

Abstract

Global climate change is altering the ecology of organisms across all major biomes and is likely to contribute to a rapidly increasing number of species extinctions. The effects of climate change are further exacerbated in fragmented landscapes, where isolated populations are known to be losing genetic diversity. This loss of genetic diversity is thought to impact the physiological flexibility (termed 'plasticity') that a species needs to survive the warmer, more fluctuating temperatures that are associated with global climate change. In this study we examined the thermal plasticity of adult male Aegean wall lizards (Podarcis erhardii, Lacertidae) occurring on Cycladic land bridge islands (Aegean Sea, Greece). Populations were sampled from three different size islands ranging from 0.01 km2 to 448 km2. Previous studies have shown that P. erhardii exhibits a predictable gradient in genetic diversity correlating with island area and time since isolation. After collection, lizards were acclimated under identical thermal lab conditions for three weeks after which lizards were divided into control and treatment groups. Treatment groups were subjected to an elevated temperature regime for three weeks corresponding to local conditions under a warming climate while control groups were left under the initial cooler lab conditions. Thermal preference (Tp) and critical thermal maximum (CTmax) were quantified after the initial three week lab acclimation period and then again after a three week experimental manipulation period. Changes in these parameters were then used as measures of thermal plasticity. Overall conclusions from this study indicate that (i.) P. erhardii has surprisingly rigid thermal preferences, and (ii.) level of genetic impoverishment is not related to the extent of thermal plasticity in the species. Understanding how global warming might impact reptile populations isolated in fragmented landscapes will be critically important for evaluating a population’s extinction risk and aid in guiding appropriate management decisions.