Data from: A test of hybrid growth disadvantage in wild, free-ranging species pairs of threespine sticklebacks (Gasterosteus aculeatus) and its implications for ecological speciation

Ecological speciation is the evolution of reproductive isolation as a direct or indirect consequence of divergent natural selection. Reduced performance of hybrids in nature is thought to be an important process by which natural selection can favour the evolution of assortative mating and drive speciation. Benthic and limnetic sympatric species of threespine stickleback (Gasterosteus aculeatus) are adapted to alternative trophic niches (bottom browsing versus open water planktivory, respectively) and reduced feeding performance of hybrids is thought to have contributed to the evolution of reproductive isolation. We tested this “hybrid-disadvantage hypothesis” by inferring growth rates from otoliths sampled from wild, free-ranging benthic, limnetic, and hybrid sticklebacks from two lakes. There were significant differences in growth rate between lakes, life-history stages, and among years (maximum P = 0.02), as well as interactions between most factors, but not between hybrid and parental species sticklebacks in most comparisons. Our results provide little evidence of a growth disadvantage in hybrid sticklebacks when free-ranging in nature. While trophic ecology per se may contribute less to ecological speciation than envisioned, it may act in concert with other aspects of stickleback biology, such as interactions with parasites, predators, competitors and/or sexual selection, to present strong multifarious selection against hybrids