Abstract

A key question in speciation research is how ecological and sexual divergence arise and interact. We tested the hypothesis that mate choice causes local adaptation and ecological divergence using the rationale that the performance~signal trait relationship should parallel the attractiveness~signal trait relationship. We used female fecundity as a measure of ecological performance. We used a species in the Enchenopa binotata treehopper complex, wherein speciation involves adaptation to novel environments and divergence in sexual communication. We used a full‐sibling, split‐family rearing design to estimate genetic correlations (r G) between fecundity and signal traits, and compared those relationships against population‐level mate preferences for the signal traits. Animal model estimates for r G between female fecundity and male signal traits overlapped zero—rejecting the hypothesis—but could reflect sample size limitations. The magnitude of r G correlated with the strength of the mate preferences for the corresponding signal traits, especially for signal frequency, which has the strongest mate preference and the most divergence in the complex. However, signal frequencies favored by the population‐level mate preference are not associated with high fecundity. Therefore, mate preferences do not appear to have been selected to favor high‐performance genotypes. Our findings suggest that ecological and sexual divergence may arise separately, but reinforce each other, during speciation.

Highlights

  • Speciation is broadly thought to require divergence in ecological and sexual traits

  • We described univariate mate preferences for each of the above signal traits to compare each one with how the signal traits relate to variation in female fecundity

  • We report the amount of genetic variation as a coefficient of variation, following

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Summary

| INTRODUCTION

Speciation is broadly thought to require divergence in ecological and sexual traits. Specialization on different resources brings performance trade-­offs that disfavor hybridization (Coyne & Orr, 2004; Nosil, 2012); and, divergence in traits such as ornaments, mate preferences, and genitalia yields direct reproductive isolation (Andersson, 1994; Coyne & Orr, 2004; West-­Eberhard, 1983). The rationale for the hypothesis that mate choice promotes local adaptation and ecological divergence is as follows: When sexual ornaments are costly, mate preferences for individuals with attractive displays would favor those individuals better able to acquire and allocate resources to the display. We consider that to relate mate choice of ornaments to local adaptation, the key is to focus on the fecundity of the choosing females and their daughters This is a version of the hypothesis that male sexual ornaments are selected to indicate the quality of the daughters that males would produce if accepted as mating partners (Trivers, 2002; cf Miller & Moore, 2007). We used female fecundity as a measure of the ecological performance of different genotypes to test the hypothesis that mate choice causes local adaptation. We tested for a relationship between the strength of mate preferences and the amount of genetic variation in the corresponding signal traits; and, we tested for a relationship between the amount of genetic variation in signal traits and the magnitude of rG between female fecundity and the signal traits

| MATERIALS AND METHODS
| DISCUSSION
Findings
CONFLICT OF INTEREST
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