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

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 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 postcopulatory sexual traits. In accordance with previous work, we found that dietary limitat...