MICROGEOGRAPHIC GENETIC-STRUCTURE AND GENE FLOW IN HIBISCUS-MOSCHEUTOS (MALVACEAE) POPULATIONS

Microgeographic genetic variation in populations of a wetland macrophy te, Hibiscus moscheutos L. (Malvaceae), was investigated using allozym e polymorphism. The species is a self-compatible insect-pollinated per ennial, and seeds are water dispersed (hydrochory). Six hundred plants were analyzed from eight brackish and two freshwater populations with in the Rhode River watershed/estuarine system. The genetic structure o f the populations was assessed by fixation indices and spatial autocor relation analyses. The degree of genetic differentiation among sites a nd gene flow between all paired combinations of sites (M) was analyzed using three hypothetical gene how models. Fixation indices indicated almost complete panmixia within populations, and spatial autocorrelati ons showed that genotypes were randomly distributed within sites, most likely the result of water dispersal of seeds. Allele frequencies wer e significantly different among sites, and estimated F-ST indicated mo derate genetic differentiation (theta = 0.062). Genetic differences be tween populations were mostly explained by a gene Bow model that accou nted for the location of populations relative to the tidal stream. The importance of hydrochory in affecting spatial genetic structure was t hus suggested both within and among H. moscheutos populations.