Low Levels of Genetic Differentiation among Populations of the CoralInhabiting Snail Coralliophila violacea (Gastropoda: Coralliophilidae) in Regions of the Kuroshio and South China Sea
Ta-Yu Lin and Li-Lian Liu (2008) The coral-inhabiting snail, Coralliophila violacea, is a common species in IndoPacific coral reefs and usually aggregates on the surfaces of living massive Poritis corals. A previous study indicated a low genetic diversity (Nei's genetic distance of < 0.003) for C. violacea of southern Taiwan (Lin 1992). Herein, we attempted to determine whether the low genetic differentiation extends to the South China Sea (SCS) by examining allozyme variations at 6 polymorphic loci. Snails were sampled from the Kuroshio region around Taiwan and the SCS which are 1500 km apart. The mean observed heterozygosity among the 7 populations varied from 0.155 to 0.293, with all indicating heterozygote deficiencies. We detected small but significant genetic differentiation among all populations (mean FST of 0.078); however, genetic distances (Nei's D) between populations were relatively low, ranging from 0 to 0.093. There was a positive trend, although insignificant, between the geographic distance and Nei,s genetic distance (Mantel test, Z = 575.7, r = 0.66, p = 0.13). This pattern was confirmed by a UPGMA cluster analysis which showed that geographical-closed populations did not cluster together. The Kuroshio intrusion, high larval dispersal capability, and the availability of host poritid corals may be responsible for these heterogeneities.
Keywords
Coralliophila violacea, Allozyme, Population genetics, Kuroshio, South China Sea.
