MATING PATTERNS OF DARWINS FINCH HYBRIDS DETERMINED BY SONG AND MORPHOLOGY

Three species of Darwin's Finches hybridize on the Galapagos island of Daphne Major. We examined mating patterns to determine if hybrids exh ibit mate preferences. Geospiza fortis x G. scandens F-1 hybrids backc rossed to both of the parental species, whereas all backcrosses bred w ith the parental species to which they were most related, or with hybr ids. Paternal song was shown to be the crucial factor determining the mating pattern of G. fortis x G. scandens F-1 hybrids and their offspr ing. 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 x G. scanden s F-1 hybrid females paired with large G. scandens-like G. fortis male s. G. fortis x C. fuliginosa F-1 hybrids paired negatively assortative ly with respect to the size of their G. fortis mates. Non-random matin g of hybrids based on song, a non-genetic trait, has interesting evolu tionary consequences. Sang characteristics and nuclear and mitochondri al genes flow from G. fuliginosa into the G. fortis population, wherea s the direction of transfer of genetic and song information between G. fortis and G. scandens depends on which song was sung by the father o f the hybrids. (C) 1997 The Linnean Society of London.