Data from: Winner-loser effects on life history traits

Ageing of adult males could be accelerated by both high
mating/reproductive effort and fighting for mates. Testing the relative
importance of these factors is challenging, however, because males that
win fights also tend to have more mates. We used a 2 x 2 experimental
design to test how a prolonged (9 week) period of either winning or losing
fights, and either high or low reproductive effort (manipulating by
varying access to females) interact to affect male ageing and future
reproduction allocation in the mosquitofish, Gambusia holbrooki. We
measured telomere length and several life-history traits, including mating
effort and ejaculates (sperm count and velocity). After 9 weeks there were
significant differences between winners and losers in their mating effort,
but not in their ejaculates. Males with a higher past reproductive effort
(i.e. access to females) had significantly lower current mating effort and
grew more slowly. Males with a higher past reproductive effort also had
slower swimming sperm, but only if they were smaller than average in body
size. Surprisingly, neither males with a higher past reproductive effort
nor males that repeatedly lost fights had shorter telomeres. Our findings
show that past social dynamics affect how males allocate resources to
reproduction and somatic maintenance.