Russell Avery L, Buchmann Stephen L, Sabino William de O, Papaj Daniel R
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.
Department of Entomology, University of Arizona, Tucson, AZ.
J Insect Sci. 2018 Jul 1;18(4):18. doi: 10.1093/jisesa/iey083.
Sexual selection on male body size in species with a female-biased sexual size dimorphism is common yet often poorly understood. In particular, in the majority of bee species, the relative contribution of intrasexual competition and female choice to patterns of male body size is unknown. In this field study, we examined two possible components of male mating success with respect to body size in the solitary bee Diadasia rinconis Cockerell (Hymenoptera: Apidae): 1) ability to procure a mate and 2) the duration of copulation. We found that larger males were better able to procure mates and copulated for shorter periods of time. Although consistent with sperm competition theory, differences in copulation duration were slight; possibly, the shorter copulations of larger males instead reflect in copulo female choice. Consistent with this notion, males engaged in complex courtship while mounted, characterized for the first time in any bee in such detail via audio recordings and high-speed, high-definition video. The number of pulses in male courtship behavior was also positively associated with copulation duration and may have stimulated females to continue copulating, thereby potentially allowing smaller males to transfer a full ejaculate. Females were shown to be potentially polyandrous and although we did not observe precopulatory rejection in the field, captive females frequently rejected copulation attempts by captive males. Our work indicates that intrasexual competition selects for increased body size in a solitary bee.
在雌性偏向性大小二态性的物种中，对雄性体型的性选择很常见，但往往了解不足。特别是在大多数蜜蜂物种中，同性竞争和雌性选择对雄性体型模式的相对贡献尚不清楚。在这项实地研究中，我们研究了独居蜜蜂迪阿达西亚·林科尼斯·科克雷尔（膜翅目：蜜蜂科）中雄性交配成功与体型相关的两个可能因素：1）获得配偶的能力和2）交配持续时间。我们发现体型较大的雄性更有能力获得配偶，且交配时间较短。虽然这与精子竞争理论一致，但交配持续时间的差异很小；可能的是，体型较大的雄性较短的交配时间反而反映了交配过程中的雌性选择。与此观点一致的是，雄性在交配时会进行复杂的求偶行为，通过录音以及高速、高清视频首次如此详细地对任何蜜蜂的这种行为进行了描述。雄性求偶行为中的脉冲数量也与交配持续时间呈正相关，可能刺激雌性继续交配，从而潜在地使体型较小的雄性能够射出完整的精液。研究表明雌性可能是多配偶的，虽然我们在野外没有观察到交配前的拒绝行为，但圈养的雌性经常拒绝圈养雄性的交配尝试。我们的研究表明，同性竞争促使独居蜜蜂的体型增大。
