Abstract: The genusLigia belongs to the most primitive terrestrial isopods with biggest body size, and is known as the intermediate form between marine and strictly terrestrial isopods. There are 42 species in the genus worldwide based on the traditional taxonomic classification. Most of those species are coastal species, with only eight species dwelling in inland. Molecular systematic analysis revealed high level of intraspecific genetic divergence, suggesting limited migrationability ofLigia. Geographical isolation affected the gene flow among different populations, consequently resulting in the species differentiation and formation. On the basis of molecular phylogeny researches, this study defined three research hotspots, including PanCalifornia Peninsula group, Hawaii Islands group and China JapanKorea East Asia group. Although some progresses have been achieved, there are still some problems, including lack of basic biological description of statistical samples, deficient fundamental ecological researches and low-level academic research in underdeveloped regions. Therefore, it is important for the scientific communities to enhance the comparability of data, encourage fundamental researches, conduct international collaboration, and construct an open database.

Key words: Ligia, species identification, molecular systematics.