Data from: Social group composition modulates the role of last male sperm precedence in post-copulatory sexual selection

In many species, the order in which males mate with a female explains much
of the variation in paternity arising from post-copulatory sexual
selection. Research in Drosophila suggests that mating order may account
for the majority of the variance in male reproductive success. However,
the effects of mating order on paternity bias might not be static but
could potentially vary with social or environmental factors. To test this
idea, we used an existing dataset, collated from an experiment we
previously published (Morimoto et al. 2016), with the addition of
unpublished data from the same experiment. These previous experiments
manipulated larval density in Drosophila melanogaster which generated
variation in male and female body size, assembled groups of individuals of
different sizes, and measured the mating success and paternity share of
focal males. The data presented here provide information on each focal
male’s mating order and the frequency in which focal males remated with
the same females (‘repetitive matings’). We combined this
information with our previously reported focal male reproductive success
to partition variance in paternity into male mating order and repetitive
matings across groups that differed in the body size composition of males
and females. We found, as expected, that male mating order explained a
considerable portion of the variance in male paternity. However, we also
found that the impact of male mating order on male paternity was
influenced by the body size composition of groups. Specifically, males
that tended to mate last had a greater paternity advantage, and displayed
lower variance, in groups containing a heterogenous mixture of male body
sizes than in groups with a single male body size. Repetitive mating only
had a minor contribution to the variance in male paternity share across
all experiments. Overall, our findings contribute to the growing body of
research showing that post-copulatory sexual selection is subject to
socio-ecological influences.