Phylogeography and the genetic structure of the land-locked freshwater prawn Macrobrachium asperulum (Crustacea: Decapoda: Palaemonidae) in Taiwan

Macrobrachium asperulum is a land-locked macroinvertebrate species of freshwater prawn, which inhabits a wide range of freshwater bodies and has an abundant pan-island distribution in Taiwan. In this study, we used mitochondrial (mt) DNA fragment sequences of the large subunit ribosomal RNA (16S rRNA) gene and the cytochrome oxidase subunit I (COI) gene to examine the phylogeographical pattern and the genetic structure of M. asperulum in Taiwan. Genealogic reconstructions present four lineages distributed in three geographical regions. Analysis of molecular variance (AMOVA) shows a significant genetic structure across all hierarchical levels, indicating that genetic variance is geographically subdivided. The high genetic structure of within-catchment or within-river populations implies that the freshwater prawn M. asperulum with a land-locked life cycle has a more-limited dispersal ability. The spatial divisions are probably correlated with two dispersal routes from the Asian mainland during the tectonic evolution of Taiwan. Subsequently, the population genetic structure is deeply influenced by the periodic oscillation of glaciations, followed by fragmentation due to the formation of geographical barriers, which resulted in rare contemporary gene flow. Population divergences indicate coalescent events between populations of China (Ming River) and Taiwan, dated to between the late Pliocene and early Pleistocene (2.63-1.78 myr). The high diversity of the genetic structure of eastern populations suggested multiple artificial introductions mainly from rivers of west-central Taiwan, and this has permitted lineage sorting and random drift.