Abstract

The distribution of genetic variation among five isolated sites of the riparian species Helmholtzia glaberrima (J.D.Hook) was examined in Toloona Creek (28°13′S, 153°07′E) by using dominant amplified fragment length polymorphism (AFLP) markers. From the 137 fragments assessed, analysis of molecular variance (AMOVA) showed that most genetic variability occurred within sites (68%), although high (32%) variation also occurred among sites. Highly significant pairwise θ estimates among all sampled sites suggest that gene flow is restricted in H. glaberrima. Levels of within-site diversity were intermediate and significantly different across the sampled sites. Significant levels of linkage disequilibrium were detected at all sites except TC3. Differences in linkage disequilibrium and genetic diversity among the sites suggest that sites may have been founded by different numbers of colonists. Mantel tests found no correlation between geographic and genetic distance and significant levels of linkage disequilibrium were detected at the total site level, supporting a non-equilibrium model of population structure. The observed pattern of non-equilibrium population structure and genetic variation in H. glaberrima are best explained by a classical metapopulation model.