Mating patterns of Darwin's Finch hybrids determined by song and morphology

Abstract

Three species of Darwin's Finches hybridize on the Galapagos island of Daphne Major. We examined mating patterns to determine if hybrids exhibit mate preferences.Geospiza fortis×G. scandensF1hybrids backcrossed to both of the parental species, whereas all backcrosses bred with the parental species to which they were most related, or with hybrids. Paternal song was shown to be the crucial factor determining the mating pattern ofG. fortis×G. scandensF1hybrids and their offspring. Song is culturally inherited, transmitted faithfully from father to son (with few exceptions) as a result of an imprinting-like process. Size also contributes to the choice of mates.G. fortis×G. scandensF1hybrid females paired with largeG. scandens-likeG. fortismales.G. fortis×G. fuliginosaF1hybrids paired negatively assortatively with respect to the size of theirG. fortismates. Non-random mating of hybrids based on song, a non-genetic trait, has interesting evolutionary consequences. Song characteristics and nuclear and mitochondrial genes flow fromG. fuliginosainto theG. fortispopulation, whereas the direction of transfer of genetic and song information betweenG. fortisandG. scandensdepends on which song was sung by the father of the hybrids.