Exotic Plants
Five centuries ago virtually all plants in the West Gulf Coastal Plain were native. The exceptions were horticultural crops -- maize, beans, squashes -- brought from Mexico. Today, between 15% and 25% of the species are naturalized exotics (i.e., non-natives that survive without cultivation). If all cultivars were included, the number would be much greater.
Ubiquitous introductions include Chinese tallow tree and kudzu. Many lakes and impoundments are choked with water-hyacinth, hydrilla, and giant salvinia.
Rare Species
Many rare plants occur in the West Gulf Coastal Plain, of which approximately one quarter are endemic or near-endemic to the West Gulf Coastal Plain. Although the West Gulf Coastal Plain is phytogeographically closely related to the East Gulf Coastal Plain, many eastern species do not cross the Mississippi Embayment.
Some species are rare disjuncts, for example, dwarf pipewort. Whether such species are the remnants of once wide-spread and continuous populations or recent arrivals from the east by long distance migration is largely unknown, but fragmentation and recolonization appears to explain this pipewort’s distribution. The other disjunct species have not been studied, but it is likely that with the end of the Ice Age and the northward and westward expansion of species from the general Florida refugium and the northward and eastward expansion from the southern Texas/Mexico refugium, plants have been spreading over the landscape for the last ten thousand years and are still doing so.
Endemics
Recent research indicates that the Atlantic/Gulf Coastal Plain ranks among the world’s top biodiversity “hotspots.” Of a total native flora of about 5500, approximately 1500 (28%) are endemic. There are, additionally, almost 50 endemic genera and 1 endemic family in the region. With only 8% of the area of North America north of Mexico, the Coastal Plain is second only to the Californian Floristic Province of which 48% of the flora are endemics or near-endemics. There are more carnivorous plant endemics in the Atlantic and Coastal Floristic Province than anywhere else in the world.
Other important local centers of plant endemism are well known (e.g. the Apalachicola and Lake Wales regions of Florida), but the significance of the West Gulf Coastal Plain has received almost no attention in published literature and has been portrayed as largely endemically depauperate. However, the West Gulf Coastal Plain constitutes a regional center of endemism with about 100 species, and including 3 genera. 51% of these are specific to xeric sandylands, which, in area cover no more than 5% of the West Gulf Coastal Plain. The next most important communities in numbers of endemics are bogs/wetland pine savannas and glades/barrens/weches barrens, each with 9% of the total and which occupy 10% and 1% of the total area of the West Gulf Coastal Plain, respectively.
