Abstract
A total of 305 individuals from a hybrid population of North American tree frogs was characterized for allozyme and mitochondrial DNA (mtDNA) genotype. Species-specific mating behaviors had suggested the potential for directional hybridization, in which matings between Hyla cinerea males and Hyla gratiosa females numerically predominate over the reciprocal combination. Such directional bias leads to predictions about expected distributions of the female-transmitted mtDNA markers in F(1), backcross, and later-generation hybrids. These predictions were fully confirmed by the observed distributions of mtDNA genotypes among these allozymically inferred hybrid classes. Results exemplify the significance of stereotyped mating behaviors in determining the genetic architecture of a hybrid population.