Historical and Contemporary Genetic Structure of a Freshwater Gastropod Chilina dombeyana in the Biobío River, Chile

The spatial architecture as well as anthropogenic factors operating at different temporal and spatial scales are shaping demography, connectivity and population genetic structure of species inhabiting river ecosystems. Chilina dombeyana is a freshwater pulmonate gastropod with direct development (absence of a free larval phase) inhabiting the basin of the Biobío River, Chile (36°S). Despite its wide range of distribution and common use as a bioindicator species, there are no studies evaluating spatial patterns of its genetic diversity and potential factors driving these patterns. In this study we analyzed population genetics of Chilina dombeyana based on samples from 15 locations along the Biobío River covering more than 300 river kms. We used both microsatellite and mitochondrial markers. Results showed that C. dombeyana has a moderate genetic variability (range Ho=0.30-0.56), with the lowest values associated with populations of the upper basin. Population structuring was evident, and two clades represented in the haplotype network separate sites located in portions of the river with greater slopes from the rest of the localities. In addition, there was signal of historical demographic bottleneck. According to the cluster analysis, populations showed spatial subdivisions, evidencing a pattern of IBD (r=0.59, P<0.0003). Although C. dombeyana is widely distributed in rivers of Chile, its low dispersal abilities and specific habitat requirements make this species very sensible to the strong increase of anthropogenic disturbances affecting river ecosystems in recent decades.

Financing: Postdoctoral FONDECYT 3140561 to JB and FONDECYT 1130868 to AB. We also thank EULA Center, University of Concepción (PMBB Project), Chile, for its support during field trips and for providing environmental data.