Data from: Disentangling the costs of male harassment and the benefits of polyandry for females

Many studies quantify how polyandry affects female fitness by allowing
females to mate with one or several males. But even if the number of
matings is standardised, such studies conflate any costs of interacting
with males with potential benefits of receiving sperm from multiple mates,
obscuring the benefits of polyandry. We conducted a 2x2 factorial
experiment on the mosquitofish, Gambusia holbrooki to quantify the
independent effects of male harassment and polyandry. We artificially
inseminated virgin females with sperm from either one or five males.
Females were housed in the presence or absence of reproductively-ablated
males who could harass, but not mate with them. Our design ensured that
the number of males inseminating a female was independent of the level of
male harassment and the number of matings she received. Females not housed
with males were instead housed with immature females to maintain densities
across treatments. Unexpectedly, females that experienced sexual
harassment were more likely to give birth, had shorter gestation periods
and gave birth to larger broods. Furthermore, polyandrous females were
more likely than monandrous females to give birth, and their sons reached
maturity faster than those of monandrous females. We found no detectable
costs to females of male harassment when the direct costs of mating were
absent and that, in the absence of mating costs, there are direct and
indirect fitness benefits of being inseminated by multiple males. If the
costs of the act of mating are small or absent, polyandry will benefit
female G.holbrooki producing their first brood.