Genetic subdivision and morphological variation in a freshwater snail species complex formerly referred to as Viviparus georgianus (Lea)

Abstract

Genetic and morphological variation was studied in a brooding (ovoviviparous) and morphologically variable freshwater snail [ Viviparus georgianus (Lea)] species complex in southern Georgia and Florida. Eleven populations were clustered into three genetically isolated, allopatric groups characterized by 7 to 14 diagnostic loci out of the 38 loci examined. These allopatric groups were identified as V. georgianus (in eastern and southern Florida), V. limi (in the Ochlockonee River) and V. goodrichi (in the Florida panhandle). Nei's standard genetic distances between the species were large (0.23-0.52) compared to intraspecific distances (O.OCr0.06). Hierarchical F-statistics for differentiation among sites within drainage systems (FsD) for V. goodrichi and V. georgianus were large (0.519 and 0.387, respectively). The F,., values (differentiation among drainage systems within the total area sampled) were negative or close to zero, so most of the intraspecific genetic differentiation was due to differences among populations within drianage systems, rather than to differences among systems. Canonical discriminant analysis of nine shell morphological measurements separated all three species with little overlap. Principal components analysis of the shell morphology revealed intraspecific variation among sites possibly due to environmental effects. This study demonstrates the marked genetic and morphological variation among and within drainage systems in freshwater prosobranchs.

Ecological and Taxonomical Characterizations of some Molluscan species in Irrigated Nile Channels, (Rayahs), Egypt

“…These morphometric descriptions did not match with current genetic taxonomy, which suggested Viviparidae as the corresponding family of Gastropod sp.-1. However, morphology of the animal may be affected by environmental pressures, such as temperature, precipitation, and salinity (Katoh and Foltz, 1993) which may hinder the accurate description of the same animal from different localities. However, the taxonomy of Viviparid species have been suffered from, limitation of anatomical and molecular data, leaving gaps in taxon determination levels (Strong et al, 2008;Sengupta et al, 2009).…”

Morphological and allozymic variation within and between populations of Bythinella Moquin-Tandon, 1855 (Gastropoda: Prosobranchia). II. Phenetic analysis

“…Among freshwater snails, Nei values range from 0.000 to 0.057 in different Viviparus species (KATOH & FOLTZ 1994, FALNIOWSKI et al 1996; 0.000-0.180 in Biomphalaria glabrata ( MULVEY et al 1988); 0.051-0.191 in various species of Oncomelania (DAVIS et al 1994). For Hydrobiidae the following values were found: 0.000-0.012 in Hydrobia (DAVIS et al 1988), 0.000-0.118 in Graziana (HAASE 1994) and 0.065-0.428 in the artesian spring inhabitant Fonscochlea zeidleri (PONDER et al 1995).…”

NADP-dependent isocitrate dehydrogenase of Astyanax scabripinnis (Pisces, Characidae) from three altitudes at Grande Stream, Campos do Jordão, SP

“…Only 17.8% of the total gene diversity was attributed to differences between populations, i.e., 82.2% of the remaining gene diversity was due to within-total population variability. According to Katoh & Foltz (1994), the high genetic differentiation (F st = 0.321) among populations of the fish Valencia hispanica, excluding the mixed population, suggests reduced gene flow, allowing populations to adapt to local environments. The population subdivision (F st = 0.178) detected among A. scabripinnis populations indicates a interruption of genetic exchange among them.…”