Rare Plants of the Florida Scrub, USA
I. Jack Stout
Forty-five plant species found in Florida scrub (USA) have been recognized as endangered or threatened with extinction under the Endangered Species Act (28) or comparable state regulations (45). An additional three species are recognized as rare for a variety of reasons. Many of these species are endemic to the Lake Wales Ridge of central peninsular Florida. Fewer rare species are associated with scrubs found elsewhere within the peninsula, along the Atlantic and Gulf coasts and in the panhandle. Of the seven categories of rarity defined by Rabinowitz (1981), nearly all of the species exhibit small geographic ranges and narrow habitat specificity. Population sizes tend to be small everywhere, but exceptions do occur. Life history strategies represented include (1) obligate seeders, (2) resprouters and seeders, and (3) seed bank reseeders. These strategies have evolved in the face of periodic, catastrophic fires that tend to destroy most of the aboveground biomass of the Florida scrub. Rare plants show a mixture of these life history strategies. Nearly all of the rare plants depend on openings or gaps in the vegetation with exposed mineral soil and little or no litter accumulation for recruitment or long-term survival. Several land acquisition programs are involved in acquiring lands necessary to ensure the potential survival of rare Florida scrub plants.
Genetic Diversity in Rare Southeastern Plants
Mary Jo W. Godt
J. L. Hamrick
We surveyed the plant allozyme literature to summarize genetic diversity and structure data for rare seed plants from the southeastern United States. Fifty-two taxa were identified. These phylogenetically diverse taxa included 32 genera in 26 plant families and represented several life forms, including annuals (5), herbaceous perennials (31), and woody plants (16). We speculated that southeastern taxa would have more genetic diversity compared to endemic plants overall, since southeastern plant species are located close to glacial refugia, and hence may have experienced less severe founder effects and higher rates of gene flow upon re-colonization. Rare southeastern plants had a significantly greater proportion of polymorphic loci, and more alleles per polymorphic locus than other endemics. Overall, genetic diversity within rare southeastern plant species reflected nearly the entire range of genetic diversity found among seed plants. Comparisons of rare southeastern species with their more widespread congeners indicated that rare species were comparatively genetically depauperate, but these results were not universal. Allozyme analyses of several rare plants in the southeastern United States are highlighted to illustrate the insights empirical genetic studies can provide into the biology of these species. These analyses support generalities of previous allozyme reviews, and re-emphasize the importance of empirical genetic studies for rare plant conservation and management.