Factors regulating the invasive success of an alien frog: A comparison of the ecology of the native and alien populations

Abstract

We examined niche occupancy of Discoglossus pictus, an anuran recently established in Europe, comparing the niches of native (North Africa) and alien populations (south-western Europe) at two spatial scales to determine whether adaptive divergence had occurred between these two populations. Additionally, we determine whether the alien species showed a wider larvae niche and higher phenotypic variability compared with co-occurring anurans. We characterized the breeding habitats and the climatic space occupied by native and alien groups of populations of D. pictus and examined morphological traits of D. pictus and sympatric anuran larvae. Our results revealed no divergence in breeding habitat use between native and alien populations. A shift was observed between the realized niches occupied by the native and alien populations, but this shift might only reflect cryptic niche conservatism. The range of reproductive habitats selected by D. pictus was not wider than those of most native species. In the invaded range, D. pictus showed morphological overlap with some native species and broader phenotypic variability, but the adaptive advantages of this latter attribute were uncertain. Our results suggest that the invasive capacity of this species depends on favourable abiotic conditions rather than on its adaptive advantages over native anurans