Molecular analysis of the distributions of the invasive Asian clam, Corbicula fluminea (O.F. Müller, 1774), and threatened native clam, C. leana Prime, 1867, on Kyushu Island, Japan

The invasion of the Asian clam, Corbicula fluminea (O.F. Müller, 1774), has caused serious ecological and economic problems worldwide. In the Japanese archipelago, C. fluminea has been identified using morphological characteristics in most distribution surveys. However, a recent study has shown that morphology alone cannot be used to identify C. fluminea due to its superficial similarity to the related native species C. leana Prime, 1867. Consequently, the present distribution of C. fluminea is still poorly understood. We surveyed the distribution of C. fluminea on Kyushu Island, Japan, by sequencing the cytochrome b region of the mitochondrial DNA, a region that can be used to distinguish the two clam species, and found that C. fluminea was already established throughout the entire island, except at a single site where Corbicula clams comprised solely of C. leana. In response to this serious situation, we suggest using PCR-RFLP method, which was employed here, to distinguish the two clam species for more effective and rapid surveys.