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.