Measures of male reproductive performance across mating events

The cost of reproduction is well studied in females but only recently have
the costs of mating been investigated in males. Research suggests that
males allocate resources between subsequent mating events, resulting in
differential success across mating bouts. Selection should favor
allocation strategies that match the likelihood of successive matings. The
complexity of the system, however, suggests that one fixed strategy is
unlikely to be universally favored and thus I predict that genetic
variation for different allocation strategies will be segregating in
natural populations. To test this, I measured several components of
reproductive performance in eight inbred genotypes of Drosophila
melanogaster across three sequential mating events. As predicted, there
was genetic variation in how previous experience affected a male’s
reproductive performance for both the proportion of matings that produced
offspring and the proportion of offspring sired (P1). Some genotypes had
the highest success in their first matings and declined in successive
matings while other genotypes did best in later matings. Mating experience
had consistent effects across genotypes on fertility and induced
refractoriness to remating. On average, virgin matings produced the
highest fertility, and third matings most effectively induced
refractoriness. Genotype also had a significant effect on fertility. These
results have important implications for understanding how selection may
act on males when there is variation in the likelihood of multiple mating
events and could affect the evolution of male allocation strategies in the
face of perceived competitors.