Male perception of female mating status: its effect on copulation duration, sperm defence and female fitness

When females mate with multiple partners, the risk of sperm competition depends on female mating history. To maximize fitness, males should adjust their copulatory investments according to this risk. In the fruit fly, Drosophila melanogaster, the female cuticular hydrocarbon (CH) profile changes when females mate, and males use this to assess female mating status. I tested whether this cue influenced the time males spent copulating with females and if this affected male fertilization success and female fitness. I manipulated female mating status by transferring CHs from either virgin or mated females to virgin females. Males copulated significantly longer with virgin females that had been coated with CHs from mated females (experimental group) than with virgin females coated with CHs from other virgin females (control group). Copulation duration did not differ between females from the experimental group and females that had already mated. To test whether differential investment in copulation affected male sperm defence and female fitness, experimental and control females were mated once to wild-type males and then either housed with males carrying a genetic marker (experiment 1) or alone (experiment 2). In experiment 1 male sperm defence was elevated when males perceived their partner as mated, and this was mainly due to females remating less. Increased male investment in copulation duration also affected female fitness, although this was reversed between experiments 1 and 2. Finally, these results also indicate that copulations are costly to males, since manipulated males copulated for longer with virgin females than they normally would, resulting in higher fertilization success.