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Many aquatic organisms have dormant stages in their life history that foster long distance dispersal and potential gene flow.Daphnia galeata is widely distributed in four main river catchments and the Tibetan Plateau across China,nuclear and mitochondrial markers are used to investigate population and genetic structure over vast geographic distances under.We observed evidence the contribution of long distance dispersal as well as genetic isolation in the landscape genetic structure of this species.Eight out of the sixty six observed COI haplotypes were shared among populations in all four catchments.Across the whole data set in China,isolation by distance is observed for both mitochondrial as well as nuclear markers,but it was highly dependent on the presence of the Tibetan populations,which were highly differentiated from the populations in the other catchments.There was a lack of strong signal of catchment for the distribution of mtDNA haplotypes and genetic structure as derived from microsatellite markers,even though the distances covered were substantial(>3 000 km).Our data suggest that D.galeata can achieve long distance dispersal and some populations with specific haplotypes can colonize habitats from the temperate to the subtropical zones.There was no strong pattern of genetic differentiation in relation to temperature or altitude when the Tibetan populations are removed from the whole dataset.The populations in the Tibetan plateau stand out and are strongly isolated from any of the others.They have the highest genetic diversity,with up to 14 private haplotypes being found in a single population.Yet,all these haplotypes seem to be derived from one single haplotype,suggesting that these populations are both very old and isolated.Our findings of long distance dispersal in the four catchments combined with high genetic differentiation among populations(mean FST=0.18)are in line with a scenario where population genetic structure is strongly impacted by colonization patterns(“Isolation-by-colonization”).The landscape genetic structure of D.galeata in China reflects both the importance of long distance dispersal as well as of reduced levels of gene flow,likely caused by priority effects or monopolization.