2002 The American Genetic Association 93:133–139 Evidence for Long Isolation Among Populations of a Pacific Cycad: Genetic Diversity and Differentiation in Cycas seemannii A.Br. (Cycadaceae)

electrophoresis. Twenty enzyme loci in 13 enzyme systems were examined. Low genetic diversity within populations (A 1.2, P 21.3, Ho 0.047, and He 0.057) and a high degree of differentiation among populations (FST 0.594) were found. This, together with low gene flow estimates, suggests genetic drift by isolation to have been most critical to the current genetic structure of the species. Inbreeding may occur to some extent (FIS 0.165). The decline in abundance of C. seemannii, coupled with the low level of genetic diversity, suggest that conservation strategies are urgently needed. Cycads are an ancient gymnosperm line-age that tends to be long lived, outcross-ing (by wind and/or insect pollination), and generally have restricted ranges (Nor-stog and Nicholls 1997). The few isozyme studies on cycads show that genetic vari-ation within populations is generally low