Genetic structure of two sympatric gudgeon fishes (Xenophysogobio boulengeriandX. nudicorpa) in the upper reaches of Yangtze River Basin

Abstract

BackgroundXenophysogobio boulengeriandX. nudicorpaare the only two species within the genusXenophysogobio(Cyprinidae, Cypriniformes), and both are endemic to the upper reaches of the Yangtze River. In recent years, due to human activities, the natural resources available to both species have declined sharply. Sympatric species with overlapping niches inevitably compete for their habitats, and genetic structure and diversity can reflect population history and their potential for adaptation to changing environments, which is useful for management decisions.MethodsIn the present study, microsatellite DNA and mitochondrial DNA (mtDNA) markers were used to investigate the patterns of population genetic structure forX. boulengeriandX. nudicorpa. Microsatellite DNA data, jointly with traditional summary statistics includingFSTandFis, were used to assess the population genetic structure by structure analysis. The mtDNA sequences were then used to examine these patterns through time to detect demographic history.ResultsXenophysogobio boulengeriandX. nudicorpaexhibited high levels of genetic diversity in Yangtze River populations, except for two populations ofX. nudicorpain the Jinsha River, which were low in mtDNA diversity.X. boulengerishowed genetic homogeneity among populations, whereasX. nudicorpaappeared to have significant geographic genetic divergence. Both species experienced a late-Pleistocene sudden population expansion in Yangtze River populations, but not in the Jinsha River populations ofX. nudicorpa.DiscussionThe genetic homogeneity ofX. boulengeripopulations might result from similar population expansion events and environment features. The geographic genetic subdivision forX. nudicorpabetween the Jinsha and Yangtze Rivers might be caused by the geographic isolation in the middle Pliocene, as well as climate and environmental heterogeneity.