Abstract
Bellamya aeruginosa is a widely distributed Chinese freshwater snail that is heavily harvested, and its natural habitats are under severe threat due to fragmentation and loss. We were interested whether the large geographic distances between populations and habitat fragmentation have led to population differentiation and reduced genetic diversity in the species. To estimate the genetic diversity and population structure of B.aeruginosa, 277 individuals from 12 populations throughout its distribution range across China were sampled: two populations were sampled from the Yellow River system, eight populations from the Yangtze River system, and two populations from isolated plateau lakes. We used seven microsatellite loci and mitochondrial cytochrome oxidase I sequences to estimate population genetic parameters and test for demographic fluctuations. Our results showed that (1) the genetic diversity of B.aeruginosa was high for both markers in most of the studied populations and effective population sizes appear to be large, (2) only very low and mostly nonsignificant levels of genetic differentiation existed among the 12 populations, gene flow was generally high, and (3) relatively weak geographic structure was detected despite large geographic distances between populations. Further, no isolation by linear or stream distance was found among populations within the Yangtze River system and no signs of population bottlenecks were detected. Gene flow occurred even between far distant populations, possibly as a result of passive dispersal during flooding events, zoochoric dispersal, and/or anthropogenic translocations explaining the lack of stronger differentiation across large geographic distances. The high genetic diversity of B.aeruginosa and the weak population differentiation are likely the results of strong gene flow facilitated by passive dispersal and large population sizes suggesting that the species currently is not of conservation concern.
Highlights
The level of genetic diversity in natural populations is determined by the interplay of mutation, migration, hybridization, drift, and selection (Harrison 1991; Vellend and Geber 2005)
We aimed to differentiate between two main competing scenarios and their potential underlying evolutionary mechanisms: (1) limited genetic divergence and high intrapopulation diversity of local populations would suggest large population sizes and good historic connectivity, (2) In contrast, low genetic diversity and strong differentiation of local populations could be the result of a sessile life style, the occurrence in lacustrine systems, large geographic distances isolating populations, and the proposed strong anthropogenic pressure
Most populations showed no signs of bottlenecks, except for Honghu Lake (HH) (P = 0.008) and QJ (P = 0.016), suggesting that most studied populations were under mutation–drift equilibrium
Summary
The level of genetic diversity in natural populations is determined by the interplay of mutation, migration, hybridization, drift, and selection (Harrison 1991; Vellend and Geber 2005). The relative role that each force plays depends on life-history traits, the mating system, and the dispersal ability of a species. Extrinsic factors such as the landscape matrix, the geographic history, and anthropogenic actions can further affect genetic diversity of natural populations (Husemann et al 2012; FernandezGarcıa et al 2014; Eberhart-Phillips et al 2015). The landscape configuration can influence dispersal, which in turn affects the population genetic structure. The geographic history of a landscape, in turn, has influenced the demographic history of the local populations, which is an important factor shaping the current genetic composition of a species.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call