MINIMAL GENETIC-VARIATION IN A MORPHOLOGICALLY DIVERSE SPECIES (FLORIDA TREE SNAIL, LIGUUS-FASCIATUS)

The Florida tree snail, Liguus fasciatus, is morphologically extremely variable, and many of the phenotypes occur in geographically isolated populations. Although only a single species of Floridian Liguus has been recognized by most recent authors, confirming evidence of the conspecific nature of the morphologically diverse populations from throughout Florida is lacking. This study involved a genetic survey of Liguus from throughout Florida, including most of the named varieties, using the technique of allozyme electrophoresis. Genetic divergence of the populations was very low. Of 34 loci examined, only one (glucose-phosphate isomerase, Gpi) was variable, and only two alleles were present at this locus. The maximum genetic distance among any two populations was 0.03. Observed individual heterozygosity was minimal (0.0 - 0.029; xBAR = 0.0015); among mollusks, only some self-fertilizing species have similar levels of heterozygosity. Although most populations are fixed for one or the other Gpi allele, both alleles are widely distributed. The distribution of alleles and low genetic diversity support the view of a single, partially self-fertilizing species that diversified within Florida after a single founder event.