Biochemical Genetics of Sunfish. II. Genic Similarity between Hybridizing Species

Electrophoretic variation in proteins encoded by 18 genetic loci was examined in 1,099 specimens of 10 species of sunfish (Lepomis), a group renowned for its ability to hybridize, both in the laboratory and in nature. Populations belonging to the same species show very little genic differentiation over considerable geographic ranges. Species pairs show major differences in allelic composition at an average of about one-half of their loci, although the range is considerable. Thus despite ability to hybridize to the F1, Lepomis species have very different gene pools. Close genic similarity is not a necessary corollary of hybridizing propensity. A dendrogram formed by a cluster analysis of genic similarity coefficients corresponds only mildly with previously developed classifications based on morphology. Biochemical species groups in Lepomis appear as follows: (1) L. cyanellus; (2) L. macrochirus, L. humilis, L. gulosus; (3) L. marginatus, L. megalotis, L. microlophus; and (4) L. gibbosus, L. punctatus, L. auritus. Groups 3 and 4 appear quite similar and could be lumped into one cohort. The rather close genic similarity of L. gulosus to L. macrochirus is surprising and is not supported by morphological evidence. The discrepancy in similarity matrices based on morphology and proteins of Lepomis species makes it clear that electrophoretic methods provide additional information relevant to the subgeneric systematics of fishes.