Behaviour 2019
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Asymmetric mate choice in sympatric vs. allopatric sister species (Poeciliidae: Brachyrhaphis)
Alexandra Duffy1, Spencer Ingley2, Trevor Williams1, Lexie Chamberlain1, Jerald Johnson1,3. 1Brigham Young University, Provo, UT, United States; 2Brigham Young University- Hawaii, Laie, HI, United States; 3Monte L. Bean Life Science Museum, Provo, UT, United States

Hybridization is often considered costly and results in selection for active avoidance of heterospecific mating, a process known as reinforcement. However, some species benefit from hybridization. This leads to the question, under what ecological circumstances is preference for a heterospecific mate favored? We investigated how mate choice behavior varied between two sister species, Brachyrhaphis roseni and B. terrabensis, which occur in divergent predation environments in allopatry, but the same predation environment in sympatry. Dichotomous mate-choice tests revealed a repeatable pattern of no preference in allopatric populations, but a convergence in their preference for the same species, B. rosenii, in sympatric populations; thus, one species displayed evidence for reinforcement while the other preferred heterospecific mates. Morphometric data mirror this pattern, with sympatric B. terrabensis populations exhibiting a more similar body shape to B. roseni populations relative to allopatric B. terrabensis populations. These results allude to B. terrabensis attempting to capture adaptive variation via hybridization in light of their reduced fitness in high predation environments.