Sagittaria secundifolia, Kral's water-plantain, is a rhizomatous aquatic herb currently known to exist only in the Little River drainage in northeastern Alabama. It is found along crevices of sandstone slabs (linear clumps) and as circular clumps among loose boulders. In 1990, the U.S. Fish and Wildlife Service designated it a threatened species because of its restricted range and because of silvicultural, agricultural, and mining activities along the banks of Little River. Genetic diversity was assessed using starch gel electrophoresis. Although low genetic diversity was expected, diversity was higher than expected compared to other Sagittaria species. Polymorphism, within and between clumps, was detected in all populations sampled. Even though reproduction is thought to be primarily clonal, there is evidence that clumps are not always composed of one genotype. Furthermore, heterozygosity was observed and flowering does occur albeit at low frequency.

Key words: Alismataceae, conservation, genetics, isozymes, Sagittaria secundifolia