LIFE-HISTORY VARIATION AND COMPARATIVE PHYLOGEOGRAPHY OF DARTERS (PISCES, PERCIDAE) FROM THE NORTH-AMERICAN CENTRAL HIGHLANDS

Phylogeography seeks to evaluate the relationship between genetic vari ation and geographic distribution of a species to examine the influenc e of historical events on divergence. Congruent phylogeographic patter ns in codistributed species indicate historical association of the tax a being compared, and the uniform action of biogeographic events in sh aping genetic variation. We sought to evaluate the congruence of patte rns of genetic variation of five closely related fish species across a well-defined biogeographic boundary. We gathered allozymic and mitoch ondrial DNA (mtDNA) sequence data for five species of darters (Percida e: Etheostomatini) from populations distributed among biogeographic re gions in the Ozark and Ouachita highlands of the south-central United States. Comparisons among species revealed noncongruence in the magnit ude of genetic divergence in both allozymes and mtDNA sequences. We hy pothesized that noncongruence resulted, in part, from differences in l ife histories of the species in our comparison. To address this hypoth esis, we evaluated the association between gene how (measured by N(e)m ) and variation in body size and fecundity variables because they have been shown to influence gene flow in fishes. Correlation analysis rev ealed an association between gene flow and fecundity (r = 0.88), but n ot with body size (r = 0.36) or reproductive investment per individual (r = -0.23). The result was similar when independent contrasts of the original variables were used in correlation analyses. Phylogeographic analysis of mtDNA sequence data indicated the importance of history, evident in gene trees of Percina nasuta and Percina phoxocephala. Dive rgence rates between these two taxa may differ because of historically persistent differences in population sizes, reflected in present-day abundance and fecundity differences. Conversely, Percina caprodes show ed little evidence of divergence in mtDNA sequences and yielded the hi ghest mean N(e)m values from allozyme data. Comparisons among closely related, codistributed taxa may help discriminate among the possibilit ies for noncongruence in biogeographic studies by allowing evaluation of the influence of life history on patterns of gene flow.