High haplotype variability in established Asian populations of the invasive Caribbean bivalve <Emphasis Type="Italic">Mytilopsis sallei</Emphasis> (Dreissenidae)

Mytilopsis sallei is one of a small number of tropical estuarine organisms known to have successfully invaded habitats outside their native range in the Caribbean. This bivalve now occurs in several major ports in East Asia, which suggests the transport of larvae and/or adults by vessels. However, little work has been done to determine transfer pathways because direct evidence is difficult to obtain. Here we test whether there is sufficient genetic variability in a mitochondrial marker of established Asian populations of M. sallei to allow for future reconstruction of invasion history. We sampled a 376-base-pair fragment of the mitochondrial cytochrome oxidase I (COI) of M. sallei for 254 individuals representing 11 populations from Singapore, India, Hong Kong and Taiwan. We found high variability with 24 positions distinguishing 15 haplotypes. Haplotype diversity ranged between 0.6 and 0.8 in eight Singapore populations, and an analysis of molecular variance showed that there was no significant genetic segregation in these populations. Observed haplotype diversity was also high in a population from Visakhapatnam, India, but was slightly lower in samples from Taiwan and Hong Kong. Preliminary data also indicate that Singapore, India, Hong Kong, and Taiwan populations may have different dominant haplotypes. These results suggest that there is sufficient genetic variability to use mitochondrial markers for reconstructing the invasion history of Mytilopsis sallei, when larger sample sizes become available.