同种雄性竞争对手的存在对星豹蛛雄蛛求偶和交配行为的影响

越来越多的研究发现,雄性产生精子(精液)也需付出代价。雄性除了依据配偶质量和竞争对手的竞争强度适应性调整生殖投入外,雄性在求偶和交配行为上也相应产生适应性反应,求偶和交配行为具有可塑性。目前雄性求偶和交配行为可塑性研究主要集中于雌性多次交配的类群中,在雌性单次交配的类群中研究甚少。以雌蛛一生只交配一次而雄蛛可多次交配的星豹蛛为研究对象,比较:(1)前一雄性拖丝上信息物质对后续雄蛛求偶和交配行为的影响,(2)雌雄不同性比对雄蛛求偶和交配行为的影响。研究结果表明,星豹蛛前一雄蛛拖丝上的信息物质对后续雄蛛求偶潜伏期、求偶持续时间和交配持续时间都没有显著影响,但前一雄蛛拖丝上的信息物质对后续雄蛛求偶强度有显著抑制作用。同时,性比对星豹蛛雄蛛求偶和交配行为都没有显著影响。可见,星豹蛛雄蛛对同种雄性拖丝上的化学信息可产生求偶行为的适应性调整,而对性比不产生适应性反应。

Effects of conspecific rivals on male courtship and mating in the monandrous wolf spider Pardosa astrigera

Male sperm or semen production is costly across diverse taxa. Consequently, depending on mate quality and the competitive intensity of rivals, males are predicted to adaptively invest their courtship and mating efforts to maximize their reproductive success, while prudently allocating their sperm. Presently, most studies on male plastic behavioral responses to rivals have mainly focused on polyandrous females. Recent studies provide evidence that male plastic behavioral responses are plentiful and varied, found in a wide range of taxa, and comprise behaviors that occur pre- or post-copulation. It is predicted that males altered aspects of their mating behavior when indirectly exposed to rival chemical cues, and directly exposed to the sex ratio or the presence, number, or density of rivals. Generally, males exhibit adaptively behavioral responses to rival cues to maximize their reproductive fitness. In contrast, we have limited information about male behavioral responses to rival cues in monandrous species. In the present study, we used the monandrous wolf spider, Pardosa astrigera, as a model system to test male plastic behavioral responses to rival chemical cues and different operational sex ratios. It is generally accepted that in wandering spiders, males depend on female silk-mediated chemical substances to search and locate mates. Besides encountering the silk of females of different periods, such as immature and mature virgin females, and mated females, males may also encounter male silk and a mix of female and male silk. Given that males gain mating opportunities via pre-copulatory mate choice, it is predicted that males may invest more courtship intensity in the silk of virgin females than those of males and/or a mix of female and male silk. When male P. astrigera individuals were exposed to the female silk previously occupied by themselves or other males, we compared the differences in male courtship latency, courtship duration, courtship intensity, and mating duration across mating treatments. Our results showed that male courtship intensity (foreleg raises per second and body shakes per second) was significantly reduced when they were exposed to female silk previously occupied by their own silk or by other males than female silk not previously occupied by males; however, there were no significant differences in male courtship latency, courtship duration, and mating duration. Although, when male P. astrigera individuals were directly exposed to different operational sex ratios, our results indicated that varied sex ratios showed a small effect on male courtship and mating behaviors. The present study concurs with our prediction, which shows that male P. astrigera possessed pre-copulatory adaptive responses to rival chemical cues, but showed limited plastic behavioral responses to operational sex ratios. To our knowledge, this is the first study to determine male plastic behavioral responses to conspecific rivals in monandrous spiders.