High temperature constrains reproductive success in a temperate lizard: implications for distribution range limits and the impacts of climate change

We investigated whether the current distribution of Lacerta schreiberi is likely to be constrained by incubation conditions. We used an incubation experiment in the laboratory to examine the effects of temperature and moisture on lizard reproductive traits, in order to clarify the ecological processes that underlie the distribution patterns of this lizard and to build more reliable mechanistic models. We then investigated to what extent range limits of L.schreiberi coincided with those predicted from incubation experiments and actual temperature variation experienced in the field. This was done by intersecting documented presence localities of the species with interpolated spatial layers of soil temperature. Reproductive success (hatching success, morphological traits and growth rates) was strongly and negatively affected by high temperature. In contrast, incubation moisture only affected neonate size and its positive effects were only realized at moderate to low temperature. Documented temperature sensitivity suggests that successful embryonic development is likely to be compromised by available thermal conditions, and that this species is unable to colonize warmer areas such as those where L.schreiberi is absent beyond its distribution range limits. An important addition is that incubation moisture does not appear to influence overall embryonic development. We would expect contemporary climate warming to cause upward elevational shifts which may be more or less critical depending on the availability of preferred habitat.