Local and landscape drivers of the number of individuals and genetic diversity of a microendemic and critically endangered salamander

Abstract

Conversion of forest ecosystems to human-modified landscapes threatens the persistence of forest-specialist species. However, the local and landscape drivers of population abundance and genetic diversity of these species are largely unknown, especially for elusive and critically endangered species, such as the salamander Pseudoeurycea robertsi—a species microendemic to the Nevado de Toluca volcano, Mexico. We assessed the relative influence of local- and landscape-scale habitat amount and habitat spatial configuration on the number of individuals and genetic diversity of P. robertsi. Given its low vagility, we expected stronger responses to local habitat amount than to landscape variables, with habitat configuration showing the weakest effects on all responses. Using multiscale and multimodel inference approaches, we tested the relative effect of local habitat amount (fallen logs volume), landscape habitat amount (forest cover) and landscape configuration (forest edge density and forest fragmentation per se) on the number of salamanders and its genetic diversity. The number of individuals was more strongly related to local and landscape variables than genetic diversity. As predicted, local habitat amount showed stronger positive effects on number of individuals and number of alleles than forest cover. In addition, all response variables increased in landscapes with lower edge density. Fragmentation per se showed weak influence on all responses. Fallen logs volume is a major driver of this forest-specialist salamander. Yet, edge density also shapes salamander populations, especially the number of individuals. Retaining fallen logs in forests and increasing forest core areas are critical for salamander conservation.