Molecular approaches uncover cryptic diversity in intertidal Ligia isopods (Crustacea, Isopoda, Ligiidae) across the southern Africa coastline

Recent phylogeographic studies along the coastline of southern Africa have uncovered cryptic diversity in several coastal invertebrates, including direct developing crustaceans in the superorder Peracarida. These findings indicating the possible existence of additional cryptic diversity in other yet to be studied peracarids, particularly those known to harbor said cryptic diversity in other regions of the world. Isopods in the genus Ligia are one such taxon. They inhabit patchy rocky beaches, are direct developers, avoid the open water, and exhibit other biological traits that severely constrain their dispersal potential (e.g., poor desiccation resistance). These traits are thought to have led to long-term isolation of populations, and allopatric diversification in Ligia species around the world; however, Ligia species in southern Africa, where three endemic Ligia species of uncertain validity are known to exist, remain unstudied to date. In this study, we used mitochondrial and nuclear markers to characterize Ligia collected in 18 localities from Namibia to the KwaZulu-Natal region of South Africa. We report the presence of cryptic lineages within Ligia species in the region that suggest the need for taxonomic reevaluation of these isopod species.