GENETIC SIMILARITIES AMONG CERTAIN FRESH-WATER MUSSEL POPULATIONS OF THE LAMPSILIS GENUS IN NORTH-CAROLINA

The objective of this research was to explore ecological and genetic similarities among several southeastern freshwater mussel populations, focusing especially on two rare and potentially endangered "subspecies" of Lampsilis radiata residing in river systems in the Piedmont and coastal plain of North Carolina. Conchological analyses and the examination of genetic identity patterns derived from 11 electrophoretic loci in six different populations or species formed the basis of our interpretations. Two currently recognized subspecies of Lampsilis radiata (radiata and conspicua) are now quite rare in North Carolina waters, and one, L. r. conspicua, may be endemic to the state. However, we find that in spite of the difference in unadjustable sample mean shell length, they do not differ in general shell morphometry. For example, covariance analyses indicated homogeneity of shell length-height regression coefficients, and no difference in adjusted mean lengths. A similar conchological comparison of these two "subspecies" with the smaller sized recently described Lampsilis fullerkati of Lake Waccamaw also failed to find any significant conchological differences among these populations. Nei's unbiased genetic distance and Rogers modified genetic distance derived from electrophoretic analyses consistently separated on established Ellipito, Leptodea and Lampsilis species. However, these genetic distance measures did not distinguish between the two rare Lampsilis radiata "subspecies" nor between these two groups and Lampsilis fullerkati: Nei's unbiased identity ranged from 0.945 to 0.978 among these three populations. Phenograms and a Wagner tree derived from Rogers distance supported evolutionary similarities among these three populations. We also found evidence of site effects (conchological differences in different habitats) in Lampsilis cariosa and Leptodea ochracea, the two species examined for such a phenomenon. Genetic identity values among these intraspecific but allopatric populations ranged from 0.9220. 982. We suggest that until contrasting genetic and distinctive biological data are forthcoming, the two "subspecies" of L. radiata and possibly L. fullerkati simply be considered as a multiple population complex of Lampsilis radiata.