Multiple unrelated founding events for the long-distance Pleistocene dispersal of the Salangid, Neosalanx taihuensis: A general demographic model for inshore-orientated freshwater fish

The Salangid icefish Neosalanx taihuensis (Salangidae) originated from inshore of the East China seas and underwent adaptive freshwater radiation from the mid-Miocene to the early Pleistocene. The distribution of its genetic diversity presents a random pattern inconsistent with contemporary hydrological structure. In the present study, coalescent simulations were used to analyze its Pleistocene dispersal history. Population history simulation supported the hypothesis of long-distance dispersal during the Pleistocene based on multiple unrelated founding events. This analogous genetic pattern has been described for other inshore-orientated freshwater fish, and may represent a general history dispersal model for the phylogeography of these species. From network analysis, three subclades (Clades 1-3) grouped consistently with three probable ancestral haplotypes (H36, H27, and H33). Demographic analysis also revealed that the ancestral haplotype group (Clade 1) dispersed into freshwater during an interglacial age about 0.35 Ma, while Clades 2 and 3 dispersed about 0.12 and 0.145 Ma, respectively. The N. taihuensis population remained relatively small for a considerable amount of time during the Pleistocene ages, with population expansion events mainly occurring after the last glacial maximum (LGM).

Alternative history dispersal models tested, gene tree and proposed evolutionary history of N. taihuensis.Research highlights► Population history simulation supporting the random genetic pattern of N. taihuensis was based on multiple unrelated founding events. ► The ancestral haplotype groups of this species dispersed into freshwater during inter-glacial period, with population expansion events mainly occurring after the last glacial maximum. ► This dispersal pattern may represent a general history dispersal model for other inshore-orientated freshwater fish in this area.