Allozyme variation in three eastern United States species of Aeschynomene (Fabaceae), including the rare A. virginica

Starch gel electrophoresis and allozyme analyses were employed to assess the systematic relationships among the morphologically similar Aeschynomene virginica, A. indica, and A. rudis. Electrophoretic data were also used to compare genetic variation in the rare A. virginica, designated a threatened species throughout most of its geographical range, and the widespread A. indica. Nei's genetic identity based on allele frequencies at 20 loci in eight populations of A. virginica, 11 populations of A. indica, and 1 population of A. rudis is 0.651 between A. virginica and A. indica, 0.789 between A. virginica and A. rudis, and 0.711 between A. indica and A. rudis. These data reveal that the species are well differentiated, with no evidence of interspecific hybridization. Both A. virginica and A. indica have low levels of polymorphism at isozyme loci. However, indices of genetic variation, including percent loci polymorphic and average heterozygosity, indicate that A. indica maintains more electrophoretic variation within populations than A. virginica.