Genetic structure of a scleractinian coral, Mycedium elephantotus, in Taiwan

The genetic structure of Mycedium elephantotus (Pallas, 1766) populations f rom three regions around Taiwan was examined using allozyme electrophoresis . Eight loci were scored from seven enzyme systems. Seven loci were polymor phic under the 95% criterion. The high ratio of observed to expected genoty pic diversities at the collection sites (G(O):G(E) = 0.8 to 1.0) indicate t hat M. elephantotus propagates predominantly by sexual reproduction. Allele frequencies of M. elephantotus differed significantly among regions (D=0.0 24 to 0.256, F-ST = 0.032 to 0.218, p < 0.001), while populations among col lection sites within each region were homogeneous (D = 0.000 to 0.015, F-ST = 0.010 to 0.022, p > 0.05). Genetic differentiation between populations f rom southern Taiwan and the Penghu Islands is greater than that between sou thern and northern Taiwan populations, although the former two regions are much closer geographically. The UPGMA dendrogram based on Nei's unbiased ge netic distance showed a clear subdivision of populations into two groupings , northern Taiwan/Penghu Islands and southern Taiwan. A higher level of gen e flow was found between M. elephantotus populations in northern Taiwan and the Penghu Islands (N-m = 7.56) than that between populations in southern Taiwan and other regions (N-m,= 0.90 to 1.72). The pattern of genetic subdi vision among regions is consistent with the pattern of ocean currents, indi cating that genetic differentiation is likely driven by surface circulation vicariance.