Data from: Is diversification in male reproductive traits driven by evolutionary trade-offs between weapons and nuptial gifts?

Many male animals have evolved exaggerated traits that they use in combat
with rival males to gain access to females and secure their reproductive
success. But some male animals invest in nuptial gifts that gains them
access to females. Both these reproductive strategies are costly in that
resources are needed to produce the weapon or nuptial gift. In closely
related species where both weapons and nuptial gifts are present, little
is known about the potential evolutionary trade-off faced by males that
have these traits. In this study, we use dobsonflies (order Megaloptera,
family Corydalidae, subfamily Corydalinae) to examine the presence and
absence of enlarged male weapons versus nuptial gifts within and among
species. Many dobsonfly species are sexually dimorphic, and males possess
extremely enlarged mandibles that they use in battles, whereas in other
species, males produce large nuptial gifts that increase female fecundity.
In our study, we show that male accessory gland size strongly correlates
with nuptial gift size and that when male weapons are large, nuptial gifts
are small and vice versa. We mapped weapons and nuptial gifts onto a
phylogeny we constructed of 57 species of dobsonflies. Our among-species
comparison shows that large nuptial gift production evolved in many
species of dobsonfly but is absent from those with exaggerated weapons.
This pattern supports the potential explanation that the trade-off in
resource allocation between weapons and nuptial gifts is important in
driving the diversity of male mating strategies seen in the dobsonflies,
whereas reduced male–male competition in the species producing large
spermatophores could be an alternative explanation on their loss of male
weapons. Our results shed new light on the evolutionary interplay of
multiple sexually selected traits in animals.