Vol. 47 No. 1, 2008

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*

Institute of Marine Biology and Asia-Pacific Ocean Research Center - Kuroshio Research Group, National Sun Yat-sen University, Kaohsiung 804, Taiwan

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 F_ST 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.

Key words: Coralliophila violacea, Allozyme, Population genetics, Kuroshio, South China Sea.

*Correspondence: Tel: 886-7-5255108.  Fax: 886-7-5255100. E-mail:lilian@faculty.nsysu.edu.tw