The Abundance of Premetamorphic Newts (triturus Cristatus, T. Marmoratus) as a Function of Habitat Determinants: an a Priori Model Selection Approach

Despite the key role of premetamorphic amphibians in experimental ecology, the factors affecting their abundance has received relatively little attention in natural settings. We applied a model selection approach with AIC (Akaike's Information Criterion) to predict the abundance of embryos and larvae of crested and marbled newts (Triturus cristatus and T. marmoratus) at 32 breeding sites in western France, based on 15 variables describing the aquatic habitat, and 10 variables describing the terrestrial habitat within a 100 m radius around the pond. The best model for embryos included the variables shade and floating vegetation (highest embryo abundance in intermediate ponds), and pond size (negative correlation). Larval abundance was best explained by shade (negative correlation), and the interaction between phosphate and nitrate. Pond variables were not fully comparable to terrestrial parameters, but produced better predictive models for both embryos and larvae. Due to the high explanatory value of ecological parameters the results suggest that in a metapopulation context, deterministic population processes driven by pond succession may be more important than stochastic extinctions and recolonizations of otherwise suitable habitat patches.