Data from: Polyandrous females provide sons with more competitive sperm: support for the sexy-sperm hypothesis in the rattlebox moth (Utetheisa ornatrix)

Given the costs of multiple-mating, why has female polyandry evolved?
Utetheisa ornatrix moths are well-suited for studying multiple mating in
females because females are highly polyandrous over their lifespan, with
each male mate transferring a substantial spermatophore with both genetic
and non-genetic material. The accumulation of resources might explain the
prevalence of polyandry in this species, but another, not
mutually-exclusive, possibility is that females mate multiply to increase
the probability that their sons will inherit more-competitive sperm. This
latter “sexy-sperm” hypothesis posits that female multiple mating and male
sperm competitiveness co-evolve via a Fisherian runaway process. We tested
the sexy-sperm hypothesis by using competitive double matings to compare
the sperm competition success of sons of polyandrous versus monandrous
females. In accordance with sexy-sperm theory, we found that in 511
offspring across 17 families, the male whose polyandrous mother mated once
with each of three different males sired significantly more of all total
offspring (81%) than did the male whose monandrous mother was mated thrice
to a single male. Interestingly, sons of polyandrous mothers had a
significantly biased sex ratio of their brood toward sons, also in support
of the hypothesis.