Microsatellite variation in Bavarian populations of European grayling (Thymallus thymallus): Implications for conservation

摘要

European grayling populations in Bavaria have shown steady declines during the last 10-20 years. In order to provide guidelines for conservation strategies and future management programs. we investigated the genetic structure of 15 grayling populations originating from three major Central European drainage (the Danube, the Elbe) and the Rhine/Main) using 20 microsatellite loci. Genetic divergence between the three drainage systems was substantial as illustrated by highly significantly heterogeneity of genotype frequencies, high number of drainage-specific private alleles, high between-drainage F_(ST) values, high assignment success of individuals to their drainage of origin and the high bootstrap support for the genetic distance based drainage-specific population clusters. In agreement with earlier studies, microsatellites revealed relatively low levels of intrapopulational genetic diversity in comparison to the overall level of variation across populations. Maximum likelihood methods using the coalescent approach revealed that the proportion of common ancestors was generally high in native populations and that the estimates of N_e were correlated with the genetic diversity parameters in all drainages. The number of effective immigrants per generation (N_em) was less than one for all pairwise comparisons of populations within the drainages, indicating restricted interpopulational gene flow. Based on these findings we recommend a drainage and sub-drainage specific conservation of grayling populations in order to preserve their overall genetic diversity and integrity. For large-scale stocking actions to supplement declining or to restore extinct populations, creation of separate broodstocks for major conservation units (ESUs and MUs) is warranted.