Genotype-by-environment interactions underlie the expression of pre- and post-copulatory sexually selected traits in guppies

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    Rights statement: This is the peer reviewed version of the following article: Evans, J. P., Rahman, M. M. and Gasparini, C. (2015), Genotype-by-environment interactions underlie the expression of pre- and post-copulatory sexually selected traits in guppies. Journal of Evolutionary Biology, 28: 959–972. doi: 10.1111/jeb.12627, which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving

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© 2015 European Society For Evolutionary Biology. The role that genotype-by-environment interactions (GEIs) play in sexual selection has only recently attracted the attention of evolutionary biologists. Yet GEIs can have profound evolutionary implications by compromising the honesty of sexual signals, maintaining high levels of genetic variance underlying their expression and altering the patterns of genetic covariance among fitness traits. In this study, we test for GEIs in a highly sexually dimorphic freshwater fish, the guppy Poecilia reticulata. We conducted an experimental quantitative genetic study in which male offspring arising from a paternal half-sibling breeding design were assigned to differing nutritional 'environments' (either high or low feed levels). We then determined whether the manipulation of diet quantity influenced levels of additive genetic variance and covariance for several highly variable and condition-dependent pre- and post-copulatory sexual traits. In accordance with previous work, we found that dietary limitation had strong phenotypic effects on numerous pre- and post-copulatory sexual traits. We also report evidence for significant GEI for several of these traits, which in some cases (area of iridescence and sperm velocity) reflected a change in the rank order of genotypes across different nutritional environments (i.e. ecological crossover). Furthermore, we show that genetic correlations vary significantly between nutritional environments. Notably, a highly significant negative genetic correlation between iridescent coloration and sperm viability in the high food treatment broke down under dietary restriction. Taken together, these findings are likely to have important evolutionary implications for guppies; ecological crossover may influence sexual signal reliability in unstable (nutritional) environments and contribute towards the extreme levels of polymorphism in sexual traits typically reported for this species. Furthermore, the presence of environment-specific genetic covariance suggests that trade-offs measured in one environment may not be indicative of genetic constraints in others.
Original languageEnglish
Pages (from-to)959-972
JournalJournal of Evolutionary Biology
Issue number4
Early online date17 Apr 2015
StatePublished - Apr 2015

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