Data from: Disruptive sexual selection on body size in the polyphenic black scavenger fly Sepsis thoracica

Sexual selection has two main components, female preference and male-male
competition, which can lead males to adopt alternative reproductive
tactics to optimize their reproductive success. Two traits that
significantly influence reproductive success are body size and coloration,
as they can facilitate access to females through male contests or as
female attractors. We investigated whether, and if so which mechanism of
sexual selection contributes to the maintenance, and possibly even the
establishment, of two almost discrete male morphs in the polyphenic black
scavenger fly Sepsis thoracica (Diptera: Sepsidae): small and black, or
large and amber. We performed two complementary laboratory experiments to
evaluate the mating success of the different male morphs and the behaviors
(of both males and females) presumably mediating their mating success. We
found evidence for intraspecific disruptive sexual selection on male body
size that is mediated by male-male interactions, and significant positive
directional selection on body size that interacted with (directional)
selection on coloration, likely contributing to the origin and/or
maintenance of the threshold relationship between the two traits in this
species. The simultaneous occurrence of disruptive selection and
polyphenism in S. thoracica supports the role of sexual selection in the
intraspecific diversification of coupled traits (here body size and
coloration), which could be a speciation starting point.