Stochasticity in Sexual Selection Enables Divergence: Implications for Moth Pheromone Evolution
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Sexual selection has long been hypothesized to lead to allopatric speciation, and one possible mechanism for this is that its interaction with stochasticity, which perturbs the trait and preference equilibria, can result in different traits being preferred in different populations. Here we specifically examine the role that stochastic changes in sexual selection strength plays in the shift of predominance between pairs of preferences and traits within a single population. We first create a single-locus null model of stochasticity during frequency dependent selection and then compare it to a two-locus population genetic model with stochastic strengths of female preferences for male traits. We find some interesting differences between the two models, primarily that in the two-locus sexual selection model shifts between preference and trait regimes occur more often with both weak and strong preferences, compared to intermediate preference strengths. We discuss the implications of our results for the evolution of pheromone blends and male responses during speciation in moths, a case that seems to match the assumptions of our model.
KeywordsGenetic drift Moth Population genetic model Sexual selection Speciation Stochasticity
The authors thank J. Adamson, A. Frame, S. Dhole, J. McKinnon, and two anonymous reviewers for comments on the manuscript and N. Barton, R. Servedio and especially T. Paixão for discussion. We also thank A. Faucci, M.P. Miglietta and F. Santini for the invitation to contribute to this edition. MRS and JTR were funded by NSF DEB 0919018 EB was funded by the NSF REU supplement DEB-1026740.
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