Strong genetic structure and signs of population bottlenecks in the land snail Humboldtiana durangoensis in the Sierra Madre Occidental of Western Mexico

Phylogeographic studies of different montane biological groups in Mexico have revealed complex patterns in a broad scale but an absence of genetic structure within local mountain systems such as the Sierra Madre Occidental. In this study, we estimate the genetic structure and demographic history of the endemic land snail Humboldtiana durangoensis within this mountain range. Nine polymorphic microsatellite loci in 178 individuals from 16 localities throughout the complete geographic distribution were analyzed. Strong deviations from Hardy–Weinberg equilibrium and low levels of heterozygosity were detected in the seven genetic clusters. The gene flow between two of the main geographic regions (North and South) was symmetric (≈4 individuals). In addition, the analysis detected changes in the effective population size indicating that both geographic regions experienced a drastic reduction in their effective population size probably associated with the Pleistocene climatic changes.