Impact of female mating status and female familiarity with remating interval on the reproductive success of Propylea dissecta (Mulsant) (Coleoptera: Coccinellidae)

Remating rate is a fundamental parameter that acts on disease transmission, sexual dimorphism, and the rate of evolution of species. Recent studies have indicated that sperm production can be costly. It is thus likely that males may tailor their sperm expenditure according to female mating status and the remating interval between successive matings. In this study, we investigated the effects of male remating interval, female mating status and familiarity of females in the ladybird beetle Propylea dissecta (Mulsant). Ten-day-old adults were allowed to mate and, post disengagement, these adults were exposed to second mating opportunities, either immediately after the first mating, or 6, 18 or 24 h later. To assess the effect of female mating status, the males were subjected to mating with virgin and mated females. Similarly, for assessing the effects of female familiarity, males were subjected to mating with either familiar or unfamiliar females. With increasing remating interval individuals mated for longer, resulting in higher fecundity. Percent egg viability increased with increased remating interval and was highest at 24 h. Mated and unfamiliar females were found to be more fecund than virgin females. Mated females produced a higher number of viable eggs than virgins, suggesting that multiple mating and promiscuity are essential for maximizing the reproductive success of both sexes.

Sperm allocation in relation to female size in a semelparous salmonid

To maximize reproductive success, males have to adaptively tailor their sperm expenditure in relation to the quality of potential mates because they require time to replenish their sperm supply for subsequent mating opportunities. Therefore, in mating contexts where males must choose among females in a short period of time, as is the case with semelparous species (which die after one intensely competitive short duration breeding season), selection on sperm allocation can be expected to be a powerful selective agent that shapes the male reproductive success. We quantitatively investigated sperm allocation patterns in chum salmon in relation to perceived female quality by developing a novel method for determining the amount of sperm allocated per ejaculate during spawning bouts. We examined the relationship between sperm expenditure and the body size of paired females (a proxy of egg number and egg quality) in the absence of male–male competition in an experimental channel. The estimated amount of sperm released per spawning event was positively correlated with the size of paired females. However, the number of spawning events a female participated in, which reduces the number of eggs she spawns in each subsequent bout, did not affect this relationship. These results provide support for predictions arising from the sperm allocation hypothesis, male salmon do economize their sperm expenditure in accordance with paired female body size as predicted for their first spawning event, but males overestimate or are unable to assess the quality of females beyond size and provide more sperm than they should in theory when paired with a female that spawned previously. Overall, the observed sperm allocation pattern in chum salmon appears to be adapted to maximize reproductive success assuming female size is an honest indicator of quality, although temporal changes in a female's quality during a reproductive season should be considered when examining sperm allocation strategies.