GENETIC VARIATION AMONG POPULATIONS OF EASTERN NEWTS, NOTOPHTHALMUS VIRIDESCENS: A PRELIMINARY ANALYSIS BASED ON ALLOZYMES

The eastern newt, Notophthalmus viridescens, is widely distributed in eastern North America and has been divided into four subspecies. These subspecies differ geographically in morphology and life history, suggesting that the subspecies represent locally adapted and differentiated entities between which gene flow is significantly reduced. We investigated the relationships among subspecies by assessing population genetic structure across the range of the species. We analyzed 18 allozyme loci to examine the evolutionary relationships among the four subspecies of eastern newts: N. v. viridescens, N. v. dorsalis, N. v. louisianensis, and N. v. piaropicola. Despite moderate amounts of genetic variation, phylogenetic and phenetic analyses of the relationships among 12 sites resulted in trees that were inconsistent with the current subspecific classification. Cluster and phylogenetic analyses of allele frequency variation confirmed this, indicating an absence of significant differentiation among subspecies. Instead, populations of N. viridescens appear to cluster into groups representing geographic units that do not directly correspond to the currently recognized subspecies. The morphological and life history differences among the subspecies are not clearly associated with differentiation at allozyme loci. Recent divergence, gene flow, or phenotypic plasticity may explain the lack of correlation between genetic and morphological differentiation.