Data from: Does kin selection moderate sexual conflict in Drosophila?

Two recent studies provide provocative experimental findings about the
potential influence of kin recognition and cooperation on the level of
sexual conflict in Drosophila melanogaster. In both studies, male fruit
flies apparently curbed their mate-harming behaviours in the presence of a
few familiar or related males, suggesting some form of cooperation
mediated by kin selection. In one study, the reduction in agonistic
behaviour by brothers apparently rendered them vulnerable to dramatic loss
of paternity share when competing with an unrelated male. If these results
are robust and generalizable, fruit flies could be a major new focus for
the experimental study of kin selection and social evolution. In our
opinion, however, the restrictive conditions required for male cooperation
to be adaptive in this species make it unlikely to evolve. We investigated
these phenomena in two different populations of D. melanogaster using
protocols very similar to those in the two previous studies. Our
experiments show no evidence for a reduction in mate harm based upon
either relatedness or familiarity between males, and no reduction in male
reproductive success when two brothers are in the presence of an
unfamiliar, unrelated, ‘foreign’ male. Thus, the reduction of sexual
conflict owing to male cooperation does not appear to be a general feature
of the species, at least under domestication, and these contrasting
results call for further investigation: in new populations, in the field
and in the laboratory populations in which these phenomena have been
reported.