Genetic assessment of the threatened microendemic Pleurodeles poireti (Caudata, Salamandridae), with molecular evidence for hybridization with Pleurodeles nebulosus

摘要

Short-range endemics are high-priority conservation targets, and valuable information for their management can be obtained from assessments of genetic diversity and structure, including potential hybridization with related species, and the investigation of factors shaping their patterns of occurrence. The Edough ribbed newt, Pleurodeles poireti, is restricted to the Edough Peninsula in Algeria, and listed as Endangered in IUCN's Red List. Its range is completely surrounded by the more widespread, closely related, Algerian ribbed newt, Pleurodeles nebulosus. Here we examined patterns of genetic diversity and structure in P. poireti using mtDNA sequences of the ND4 gene and a suite of 12 polymorphic microsatellites in a sample of 193 individuals from 46 populations covering the whole range of P. poireti and neighboring populations of P. nebulosus. We also investigated the influence of environmental variables (climate, topography, soil texture and plant cover) on the patterns of occurrence of both species. Genetic data allow fine scale delineation of the ranges of the two species and provide evidence for hybridization in several localities in a broad area of overlap. Niche analyses indicate that P. nebulosus and P. poireti tend to occupy similar niches and that the hybrid zone is not associated to an ecotone. This suggests that the range boundaries of the two species may be constrained by reciprocal exclusion, although in the case of P. poireti there are additional environmental constraints. These distributional patterns could be explained by high occupation of habitats by P. poireti, hindering the penetration of P. nebulosus by a 'density blocking' effect.