In search of an honest butterfly: Sexually selected wing coloration and reproductive traits from wild populations of the Cabbage White Butterfly

Abstract Sexual selection is central to many theories on mate selection
and individual behavior. Relatively little is known, however, about the
impacts that human-induced rapid environmental change are having on
secondary sexually selected characteristics. Honest signals function as an
indicator of mate quality when there are differences in nutrient
acquisition and are thus potentially sensitive to anthropogenically
altered nutrient inputs. We used the cabbage white butterfly, Pieris rapae
(L.) (Lepidoptera: Pieridae), to investigate differences in color and
testes size in a system that is often exposed to agricultural landscapes
with nitrogen addition. We collected individuals from four sites in
California and Nevada to investigate variation in key traits and the
possibility that any relationship between wing color and a reproductive
trait (testes size) could vary among locations in the focal butterfly.
Coloration variables and testes size were positively albeit weakly
associated across sites, consistent with the hypothesis that females could
use nitrogen-based coloration in the cabbage white as an indicator for a
male mating trait that has the potential to confer elevated mating success
in progeny. However, variation in testes size and in the relationship
between testes size and wing color suggest complexities that need
exploration, including the possibility that the signal is not of equal
value in all populations. Thus these results advance our understanding of
complex relationships among environmental change and sexual selection in
the wild.