Abstract
Amynthas triastriatus (Oligochaete: Megascolecidae) is a widely distributed endemic species in Southern China. To shed light on the population genetic diversity and to elucidate the population differentiation and dispersal of A.triastriatus, a population genetic structure study was undertaken based on samples from 35 locations collected from 2010 to 2016. Two exclusive lineages within A. triastriatus-lineage A and lineage B-were revealed. Lineage A was mainly distributed at high altitudes while lineage B was mainly distributed at low altitudes in Southeast China. The genetic diversity indices indicated that the populations of A. triastriatus had a strong genetic structure and distinct dispersal histories underlying the haplogroups observed in this study. Combined with morphological differences, these results indicated a new cryptic subspecies of A. triastriatus. Lineage A was almost degenerated to parthenogenesis and lineage B had a trend to parthenogenesis, which suggested that parthenogenesis could be an internal factor that influenced the differentiation and dispersal of A. triastriatus. The divergence time estimates showed that A.triastriatus originated around Guangxi and Guangdong provinces and generated into two main lineages 2.97 Ma (95%: 2.17-3.15 Ma) at the time of Quaternary glaciation (2.58 Ma), which suggested that the Quaternary glaciation may have been one of main factors that promoted the colonization of A.triastriatus.