Data from: Resource limitation and responses to rivals in males of the fruit fly Drosophila melanogaster

Diet has a profound direct and indirect effect on reproductive success in
both sexes. Variation in diet quality and quantity can significantly alter
the capacity of females to lay eggs and of males to deliver courtship.
Here, we tested the effect of dietary resource limitation on the ability
of male Drosophila melanogaster to respond adaptively to rivals by
extending their mating duration. Previous work carried out under ad
libitum diet conditions showed that males exposed to rivals prior to
mating significantly extend mating duration, transfer more ejaculate
proteins and achieve higher reproductive success. Such adaptive responses
are predicted to occur because male ejaculate production may be limited.
Hence, ejaculate resources require allocation across different
reproductive bouts, to balance current vs. future reproductive success.
However, when males suffer dietary limitation, and potentially have fewer
reproductive resources to apportion, we expect adaptive allocation of
responses to rivals to be minimized. We tested this prediction and found
that males held on agar-only diets for 5–7 days lost the ability to extend
mating following exposure to rivals. Interestingly, extended mating was
retained in males held on low yeast/sugar: no sugar/yeast diet treatments,
but was mostly lost when males were maintained on ‘imbalanced’ diets in
which there was high yeast: no sugar and vice versa. Overall, the results
show that males exhibit adaptive responses to rivals according to the
degree of dietary resource limitation and to the ratio of individual diet
components.