Species Assignment And Comparative Phylogeograghic Studies On The Genus Ligia (Crustacea:Malacostraca:Isopoda:Ligiidea) Coastally Distributed In Chinese Mainland

Neocene climate oscillations have played an important role in shaping the geographical distribution and genetic structure of animals. Previous studies have mainly focused on the influences of paleoclimate in animals on land and fishes, but the studies of the phylogeography of species distributed along the seashores were scarce. As inhabitants of the intertidal areas, sea slaters (Ligia spp.; Malacostraca: Isopoda:Ligiidae) possess a wide geographical distribution. Moreover, their direct development means that they have lost the ability to disperse pelagically. Thus, it makes them as a good model for the investigation of paleoclimate influence on the phylogeography of animals in the seashore.In this study, a total of 528 individuals of 37 geographical populations were sampled along the seashores of mainland China. The classification, geographical distribution and phylogenetic relationship of sea slaters from the genus Ligia along the coastal China were investgated, using comparative morphological and molecular analyses based on mtDNA (coxl and 16S rDNA) and nuclear markers (H3 and PEPCK). Moreover, using coxl and 16S rDNA, the comparative genetic ananlysis of two sympatric Ligia species, such as genetic variation, population genetic structure, population historical demography and gene flow, were conducted to suggest that the response of Ligia along the coastal China to past climate change since the Neocene.The major conclusions are as follows: 1) Two species of Ligia, L. exotica and L. cinerascens, occurred along the coasts of mainland China, and an overlap in the distribution range of the two related species was found across from latitude 36°N to 39°N. 2) The population of L. cinerascens along coastal China showed no obvious geographical structures, while L. exotica further splited into two geographic subclades, of which, the whole distribution range of subclade B1 was covered by the range of L. cinerascens. 3) The climate oscillation in Neocene and Pleistocene deeply influenced the the geographical distribution pattern of Ligia. 4)’Oceanic rafting’ and anthropic activities have resulted in the development of interconnected populations, promoting the spread of Ligia spp. along coastal areas...