Population genetic structure in Nolina brittoniana (Agavaceae), a plant endemic to the central ridges of Florida

Nolina brittoniana is endemic to the central ridges of peninsular Florida. Its scrub and sandhill habitats have suffered extensive anthropogenic modification. Analysis of isozymes from populations throughout its range revealed less genetic variation than generally reported for endemic plants. Populations were well differentiated, with significant clines in allele frequency along the north-south axis of distribution. Pair-wise F-statistics calculated at four levels of population geographic substructure revealed that current and inferred historical habitat patches had similar genetic structure. We found no evidence of recent bottlenecks or changes in genetic structure due to habitat loss and fragmentation, consistent with populations having always been small, isolated and low density. Our data support preservation of populations from throughout the species' range to meet conservation objectives.