Gene-gene concordance and the phylogenetic relationships among rare and widespread pygmy sunfishes (genus Elassoma)

Pygmy sunfishes (Elassoma) are primarily lowland species with an interestin g biogeographic dichotomy: three species have broad geographic distribution s, and three are narrowly distributed (and have been recommended for threat ened or endangered status). To test phylogenetic predictions derived from t he geographic distributions of pygmy sunfishes and possible historical fact ors contributing to the threatened/endangered status of the rare species, w e reconstructed trees for two mitochondrial genes and introns of three nucl ear genes. The pattern and rate of nuclear and mitochondrial sequence evolu tion were heterogeneous within Elassoma, but relationships were generally c oncordant across gene trees, Elassoma is monophyletic and, as predicted by geographic distributions, E. evergladei, E. okefenokee, and E. zonatum cons istently branch from deeper nodes. Phylogeographic structure in mitochondri al and nuclear genes also supports an early origin of E. zonatum, Phylogene tic analyses of the five loci support widely divergent positions for the ra re species E. alabamae. Two rare species, E. boehlkei and E. okatie, are si ster taxa and are related to a widespread species, E. evergladei. (C) 2001 Academic Press.