Water transfer determines the regional spread dynamics of non-native fish species

Interbasin water transfer projects(IBWT's)have emerged as dispersal corridors for aquatic species.However,little is known about how water transfer affects regional spread dynamics,or shapes the genetic diversity patterns of non-native populations.Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many wellestablished populations in IBWT's.Here,we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China.Our objectives were to(1)reveal the genetic diversity patterns of the Shimofuri Goby during regional spread,and(2)identify its mode of spreading in water transfer systems.We observed(1)a high level of genetic diversity in non-native populations without evidence of bottleneck effects,(2)that non-native populations with a longer water transfer times had a higher private allele richness,and(3)that non-native populations showed a highly mixed genetic structure,low level of genetic differentiation,and no significant relationship between geographical and genetic distances.Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae,and are probably related to propagule pressure caused by the construction of water transfer.To manage the non-native populations of T.bifasciatus,preventive actions and physical removal should be implemented in IBWT's.