Examination of the population structure of darkbarbel catfish (Pelteobagrus vachelli) in the Upper Yangtze River, China, using novel microsatellite markers
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The darkbarbel catfish (Peltoebagrus vachelli) is a small bodied benthic fish that inhabits the Yangtze River in China and is commercially valued as food. The objectives of this project were to develop the first set of microsatellite primers specific to P. vachelli and use them to examine the levels of genetic variability and population structure of three populations collected at three sites (Yibin, Luzhou, and Song Ji) along an unfragmented stretch of the upper Yangtze River. Microsatellite primers were designed from an enriched library of genomic DNA and a total of eight primer pairs were optimized to produce reliable polymorphic PCR amplicons on a LI-COR 4200 IR2 platform. A high level of variability was detected amongst the isolated loci with the number of alleles per locus ranging from 14 – 29 and mean observed and expected heterozygosity values of 0.84 and 0.90 respectively across the entire sample set. Overall levels of genetic diversity were high within the three populations with mean observed and expected heterozygosities ranging from 0.823 – 0.869 and 0.864 – 0.921 respectively. Little evidence of genetic structure was detected (global FST = 0.0065, p < 0.05) within the sampled region and pairwise tests of differentiation were not significant (all FST p > 0.05). These results imply historically large populations of P. vachelli in the upper portion of the Yangtze River that, in the absence of artificial barriers, are part of a single panmictic unit. As plans have been put forth for construction of hydroelectric installations within the sampled region, this study provides a baseline estimate of the levels of genetic variation present in P. vachelli within the remaining undammed stretch of the Upper Yangtze River which will serve as a foundation for future analyses on the effects of river fragmentation within this region. Additionally the isolation and characterization of the microsatellites will provide useful molecular markers for a variety of other applications in this and closely related species such as parentage analysis, determination of stocks, and maintenance of genetic variation in stocking practices.