Levels and patterns of genetic variation in an Asian horseshoe crab species, Tachypleus gigas Müller, from the Malay Peninsula

Abstract: Horseshoe crabs are one of the oldest living organisms that still exist today. Given the overexploitation of horseshoe crabs around the world, and the lack of information on their populations, it is crucial that genetic variation studies are done to assess their levels and patterns of genetic variation for continuous monitoring and management of their populations. Here, five populations of the Asian horseshoe crab Tachypleus gigas sampled from along the coasts of the Malay Peninsula were studied using simple-sequence repeat (SSR) and inter-simple-sequence repeat (ISSR) markers. Different results were obtained using the two different types of markers in terms of the levels of genetic variation estimated, but both concurred that most of the genetic variations were distributed at the individual level rather than among populations of the species. Inbreeding was also observed using the SSR data, although the presence of null alleles could have influenced the estimation. Finally, both marker types revealed that T. gigas could have been subjected to the land barrier effect of the Malay Peninsula that causes populations from the Indian Ocean to be genetically differentiated from the populations from the South China Sea.