Data from: Extreme cost of rivalry in a monandrous species: male–male interactions result in failure to acquire mates and reduced longevity

Mating system variation is profound in animals. In insects, female
willingness to remate varies from mating with hundreds of males (extreme
polyandry) to never remating (monandry). This variation in female
behaviour is predicted to affect the pattern of selection on males, with
intense pre-copulatory sexual selection under monandry compared to a mix
of pre- and post-copulatory forces affecting fitness under polyandry. We
tested the hypothesis that differences in female mating biology would be
reflected in different costs of pre-copulatory competition between males.
We observed that exposure to rival males early in life was highly costly
for males of a monandrous species, but had lower costs in the polyandrous
species. Males from the monandrous species housed with competitors showed
reduced ability to obtain a mate and decreased longevity. These effects
were specific to exposure to rivals compared with other types of social
interactions (heterospecific male and mated female) and were either absent
or weaker in males of the polyandrous species. We conclude that males in
monandrous species suffer severe physiological costs from interactions
with rivals and note the significance of male–male interactions as a
source of stress in laboratory culture.