HYBRIDIZATION, SEXUAL IMPRINTING, AND MATE CHOICE

Hybridization of animal species is a special pattern of mating and hen ce a behavioral phenomenon, influenced by ecological, demographic, and individual factors. We examine demographic factors (sex ratio and mat e availability) and characteristics of individuals (song and morpholog y) in an attempt to understand the occasional hybridization of three s pecies of Darwin's finches (genus Geospiza) on the small Galapagos isl and of Daphne Major. We use field data from a 20-yr study to test five hypotheses. A relative scarcity of conspecific mates (the Hubbs princ iple) explains the hybridization of the rarer species (Geospiza fuligi nosa and Geospiza scandens) but not the common species (Geospiza forti s). Female C. fortis pair with male Geospiza fuliginosa that sing song s similar to their own fathers' songs. Morphological trait values of t heir G. fuliginosa mates were also correlated with the trait values of their fathers. Geospiza fortis females pair with G. scandens that are morphologically similar to their mothers. These results imply that he terospecific mate choice is influenced by auditory and visual imprinti ng on parental traits in early life, consistent with the findings of l aboratory studies of other groups of finches. Hybridization is most li kely to occur when imprinting syndromes of closely related species are similar.