Allozyme diversity in the endangered pitcher plant Sarracenia rubra ssp. Alabamensis (Sarraceniaceae) and its close relative S-rubra ssp. rubra

Genetic variability in the federally endangered pitcher plant Sarracenia rubra ssp. alabamensis was assessed in eight Alabama populations using starch gel electrophoresis. Ten populations of the more widespread Sarracenia rubra ssp. rubra were sampled in the southeastern United States for comparison. Fifteen allozyme loci representing 13 enzyme systems were scored for each species. In contrast to S. oreophila and S. jonesii, two previously analyzed endangered pitcher plants, genetic diversity was high for both S. rubra subspecies. Within ssp. alabamensis the percentage polymorphic loci (P-s) was 80.0, the mean number of alleles per polymorphic locus was (AP(s)) = 2.58, and expected heterozygosity (H-es) was 0.209. Genetic diversity was slightly lower for ssp. rubra (P-s = 73.3, AP(s) = 2.91, and H-es = 0.177). The proportion of total genetic diversity found among populations was fairly low for both species (G(ST) = 0.09 for ssp, alabamensis and 0.14 for ssp. rubra). Little genetic divergence has occurred between the two subspecies as indicated by the lack of diagnostic alleles, the proportion of total genetic diversity between taxa (G(ST) = 0.09), and the genetic identity estimate (I = 0.90). The relatively high genetic diversity found for ssp. alabamensis indicates that the maintenance of its evolutionary potential is possible if population sizes are maintained or increased. Low levels of genetic diversity found within small Georgia ssp. rubra populations indicate that genetic erosion may increase extinction risks for these populations.