Kim Tae Won, Christy John H, Dennenmoser Stefan, Choe Jae C
School of Biological Sciences, Seoul National University, Seoul 151-747, Korea.
Proc Biol Sci. 2009 Feb 22;276(1657):775-80. doi: 10.1098/rspb.2008.1070.
When females search for mates and their perceived risk of predation increases, they less often express preferences for males that use conspicuous courtship signals, relaxing sexual selection on production of these signals. Here, we report an apparent exception to this general pattern. Courting male fiddler crabs Uca beebei sometimes build pillars of mud at the openings to their burrows in which crabs mate. Females visit several males before they choose a mate by staying and breeding in their burrows, and they preferentially visit males with pillars. Previous studies suggested that this preference is based on a visual orientation behaviour that may reduce females' risk of predation while searching for a mate. We tested this idea by determining whether the female preference for males with pillars increases with perceived predation risk. We attracted avian predators to where crabs were courting and measured the rates that sexually receptive females visited courting males with and without mud pillars. Under elevated risk, females continued to search for mates and they showed a stronger relative preference for males with pillars. Thus, when predation risk is high, females may continue to express preferences that are under natural selection because they help females avoid predation, strengthening sexual selection for use of the preferred signal.
当雌性寻找配偶且其感知到的被捕食风险增加时，它们对使用显眼求偶信号的雄性的偏好就会降低，从而放松了对这些信号产生的性选择。在此，我们报告了这一普遍模式的一个明显例外。求偶的北方大弹涂鱼（Uca beebei）有时会在其洞穴开口处建造泥柱，螃蟹在这些洞穴中交配。雌性在选择配偶并在其洞穴中停留和繁殖之前会拜访多个雄性，并且它们优先拜访有泥柱的雄性。先前的研究表明，这种偏好基于一种视觉定向行为，这种行为可能会降低雌性在寻找配偶时被捕食的风险。我们通过确定雌性对有泥柱雄性的偏好是否会随着感知到的捕食风险增加来检验这一想法。我们将鸟类捕食者吸引到螃蟹求偶的地方，并测量了处于性接受期的雌性拜访有泥柱和没有泥柱的求偶雄性的频率。在风险增加的情况下，雌性继续寻找配偶，并且它们对有泥柱雄性表现出更强的相对偏好。因此，当捕食风险很高时，雌性可能会继续表达受到自然选择的偏好，因为这些偏好有助于雌性避免被捕食，从而加强了对使用首选信号的性选择。
