Data from: Inbreeding reveals mode of past selection on male reproductive characters in Drosophila melanogaster

Directional dominance is a prerequisite of inbreeding depression.
Directionality arises when selection drives alleles that increase fitness
to fixation and eliminates dominant deleterious alleles, while deleterious
recessives are hidden from it and maintained at low frequencies. Traits
under directional selection (i.e., fitness traits) are expected to show
directional dominance and therefore an increased susceptibility to
inbreeding depression. In contrast, traits under stabilizing selection or
weakly linked to fitness are predicted to exhibit little-to-no inbreeding
depression. Here, we quantify the extent of inbreeding depression in a
range of male reproductive characters and then infer the mode of past
selection on them. The use of transgenic populations of Drosophila
melanogaster with red or green fluorescent-tagged sperm heads permitted in
vivo discrimination of sperm from competing males and quantification of
characteristics of ejaculate composition, performance, and fate. We found
that male attractiveness (mating latency) and competitive fertilization
success (P2) both show some inbreeding depression, suggesting they may
have been under directional selection, whereas sperm length showed no
inbreeding depression suggesting a history of stabilizing selection.
However, despite having measured several sperm quality and quantity
traits, our data did not allow us to discern the mechanism underlying the
lowered competitive fertilization success of inbred (f = 0.50) males.