Mate choice and courtship preferences of hybrids between incipient species can directly influence patterns of gene flow and speciation. Here, we study mate choice in hybrids between two sympatric threespine stickleback species (i.e., the benthic and limnetic species of Gasterosteus aculeatus Linnaeus, 1758) using experimental no-choice mating trials to record the preference of hybrid females (F1 hybrids and backcrosses) toward males of the parental species. Our results indicate that hybrid females preferred males with an ancestry proportion similar to their own, and that the pattern of preference toward alternate male species was additive and nearly symmetric, suggesting that mate choice shows intermediate inheritance rather than dominance. Size-based assortative mating—previously reported to direct species mate choice in this system—did not appear to shape hybrid female mate choice among hybrids. Finally, males of the parental species based mating behavior toward hybrid females on size and shape similarity rather than ancestry proportion. This suggests that body size and body shape play significant role in interspecific interactions between males and females. Our results can elucidate the role of hybrid behaviour and preference in shaping barriers to gene flow between young sympatric species.
Han et al. (Fri,) studied this question.