Eady Paul E, Hamilton Leticia, Lyons Ruth E
Department of Biological Sciences, University of Lincoln, Riseholme Park, Lincoln LN2 2LG, UK.
Proc Biol Sci. 2007 Jan 22;274(1607):247-52. doi: 10.1098/rspb.2006.3710.
Antagonistic sexual coevolution stems from the notion that male and female interests over reproduction are in conflict. Such conflicts appear to be particularly obvious when male genital armature inflicts damage to the female reproductive tract resulting in reduced female longevity. However, studies of mating frequency, genital damage and female longevity are difficult to interpret because females not only sustain more genital damage, but also receive more seminal fluid when they engage in multiple copulations. Here, we attempt to disentangle the effects of genital damage and seminal fluid transfer on female longevity in the beetle Callosobruchus maculatus (Coleoptera: Bruchidae). Males copulating for the sixth time in succession inflicted greater levels of genital damage, but transferred smaller ejaculates in comparison with virgin males. The number of copulations performed by males was negatively related to female fecundity and positively related to female longevity, suggesting a trade-off between fecundity and longevity. However, inclusion of fecundity as a covariate revealed sperm and/or seminal fluid transfer to have a negative impact on female longevity above that caused by the fecundity-longevity trade-off. The consequences of multiple copulations on female longevity were examined. Females that mated twice laid more eggs and died sooner than those that mated once. However, incorporation of fecundity as a covariate into our statistical model removed the effect of female mating frequency on female longevity, indicating that double-mated females suffer greater mortality owing to the trade-off between fecundity and longevity. Males of this species are known to transfer very large ejaculates (up to 8% of their body weight), which may represent a significant nutritional benefit to females. However, the receipt of large ejaculates appears to carry costs. Thus, the interpretation of multiple mating experiments on female longevity and associated functional explanations of polyandry in this species are likely to be complex.
对抗性的性协同进化源于这样一种观念，即雄性和雌性在繁殖方面的利益存在冲突。当雄性生殖器结构对雌性生殖道造成损伤，导致雌性寿命缩短时，这种冲突似乎尤为明显。然而，对交配频率、生殖器损伤和雌性寿命的研究很难解释，因为雌性在多次交配时不仅会遭受更多的生殖器损伤，还会接受更多的精液。在这里，我们试图厘清生殖器损伤和精液转移对黄斑豆象（鞘翅目：豆象科）雌性寿命的影响。与处男雄性相比，连续第六次交配的雄性造成的生殖器损伤程度更高，但转移的射精量更小。雄性的交配次数与雌性的繁殖力呈负相关，与雌性的寿命呈正相关，这表明在繁殖力和寿命之间存在权衡。然而，将繁殖力作为协变量纳入分析后发现，精子和/或精液转移对雌性寿命的负面影响超过了繁殖力 - 寿命权衡所造成的影响。我们研究了多次交配对雌性寿命的影响。交配两次的雌性比交配一次的雌性产卵更多，但死亡更早。然而，将繁殖力作为协变量纳入我们的统计模型后，消除了雌性交配频率对雌性寿命的影响，这表明两次交配的雌性由于繁殖力和寿命之间的权衡而死亡率更高。已知该物种的雄性会转移非常大量的射精（高达其体重的8%），这可能对雌性具有显著的营养益处。然而，接受大量射精似乎也有代价。因此，对该物种雌性寿命的多次交配实验的解释以及对多配偶制的相关功能解释可能会很复杂。
