Centre for Evolutionary Biology, School of Animal Biology (M092), University of Western Australia Crawley, Australia.
Ecol Evol. 2013 Sep;3(9):2859-66. doi: 10.1002/ece3.667. Epub 2013 Jul 24.
Environmental and genetic stress have well-known detrimental effects on ejaculate quality, but their concomitant effect on male fitness remains poorly understood. We used competitive fertilization assays to expose the effects of stress on offensive sperm competitive ability in the beetle Callosobruchus maculatus, a species where ejaculates make up more than 5% of male body mass. To examine the effects of environmental and genetic stress, males derived from outcrosses or sib matings were heat shocked at 50°C for 50 min during the pupal stage, while their siblings were maintained at a standard rearing temperature of 28°C. Heat-shocked males achieved only half the offensive paternity success of their siblings. While this population exhibited inbreeding depression in body size, sperm competitiveness was unaffected by inbreeding, nor did the effect of heat shock stress on sperm competitiveness depend on inbreeding status. In contrast, pupal emergence success was increased by 34% among heat-stressed individuals, regardless of their inbreeding status. Heat-shocked males' ejaculate size was 19% reduced, but they exhibited 25% increased mating duration in single mating trials. Our results highlight both the importance of stress in postcopulatory sexual selection, and the variability among stressors in affecting male fitness.
环境和遗传压力对精液质量有众所周知的不利影响，但它们对雄性适应度的共同影响仍知之甚少。我们使用竞争受精实验来研究压力对鞘翅目象鼻虫 Callosobruchus maculatus 中进攻性精子竞争能力的影响，该物种的精液量占雄性体重的 5%以上。为了研究环境和遗传压力的影响，来自异交或同胞交配的雄性在蛹期被 50°C 的热休克处理 50 分钟，而它们的同胞则保持在 28°C 的标准饲养温度下。热休克雄性的进攻性父权成功率仅为同胞的一半。虽然该种群在体型上表现出近交衰退，但精子竞争力不受近交的影响，热休克压力对精子竞争力的影响也不取决于近交状态。相比之下，无论其近交状态如何，热应激个体的蛹期出芽成功率增加了 34%。热休克雄性的精液量减少了 19%，但在单次交配试验中，它们的交配持续时间增加了 25%。我们的研究结果强调了压力在后交配性选择中的重要性，以及不同压力源对雄性适应度的影响的可变性。
