Phytogeography of rare plant species endemic to the Southeastern United States.

A database of the county distribution of rare vascular plant species endemic to the southeastern United States was compiled in order to review geographic trends. A total of 482 species representing 246 genera in 95 families were identified as rare southeastern endemics. The histogram of total county occurrences for these endemic species is significantly skewed to the right, indicating that those taxa that are endemic to the southeastern United States are typically rare within the region. Six centers of endemism were identified: Central Peninsular Florida, Florida Panhandle, Southern Appalachian Mountains, Tennessee Central Basin, Mid-Atlantic Coastal Plain, and West Gulf Coastal Plain. This identification of geographic trends will assist in the proactive conservation of areas harboring large numbers of endemic taxa, and these data provide the first step towards an integrative understanding of the evolutionary ecology of endemic floras.