PDF(Pubmed)
Abstract：
The existence of adult sexual dimorphism is typically explained as a consequence of sexual selection, yet coevolutionary drivers of sexual dimorphism frequently remain untested. Here, I investigate the role of sexual dimorphism in host-parasite interactions of the brood parasitic diederik cuckoo, Chrysococcyx caprius. Female diederik cuckoos are more cryptic in appearance and pose a threat to the clutch, while male diederik cuckoos are conspicuous and not a direct threat. Specifically, I examine whether sexual dimorphism in diederik cuckoos provokes threat-level sensitive responses in Southern red bishop, Euplectes orix, hosts. I use experimentally simulated nest intrusions to test whether hosts have the capacity to differentially (i) detect, and/or (ii) discriminate between, male and female diederik cuckoos, relative to harmless controls. Overall, I found no evidence that diederik cuckoos differ in detectability, since both sexes are comparable to controls in the probability and speed of host detection. Furthermore, neither male nor female hosts discriminate between sexually dimorphic diederik cuckoos when engaging in frontline nest defences. However, hosts that witnessed a male diederik cuckoo during the trial were more likely to reject odd eggs. Moreover, experimental eggs were significantly more likely to be rejected when female bishops observed a male compared to a female diederik cuckoo. While the cryptic appearance of female diederik cuckoos does not reduce detection by hosts, it does provide the benefit of anonymity given the egg rejection costs of conspicuous male-like appearance in the nest vicinity. These findings have implications for the evolution and maintenance of sexual dimorphism across the Cuculidae, and highlight the value of testing assumptions about the ecological drivers of sexual dimorphism.
摘要：
成人性二态的存在通常被解释为性选择的结果，然而，性二态性的共同进化驱动因素经常未经测试。这里,我研究了性二态性在育巢寄生杜鹃的宿主-寄生虫相互作用中的作用，金尾尾囊。雌性杜鹃在外表上更加神秘，对离合器构成威胁，而雄性杜鹃是显眼的，不是直接的威胁。具体来说,我研究了迪德里克杜鹃的性二态性是否会引起南部红色主教的威胁级别敏感反应，Euplectesorix，主机。我使用实验模拟的巢穴入侵来测试宿主是否具有差异(I)检测的能力，和/或(Ii)区分，雄性和雌性杜鹃,相对于无害的控制。总的来说,我没有发现任何证据表明杜鹃的可检测性不同，因为两性在宿主检测的概率和速度上与对照组相当。此外，无论是男性还是女性，在从事前线巢穴防御时，都不会区分性二态的杜鹃。然而,在试验期间目睹雄性杜鹃的宿主更有可能拒绝奇数卵。此外，与雌性杜鹃相比，当雌性主教观察到雄性时，实验卵更有可能被拒绝。虽然雌性杜鹃的神秘出现并没有减少宿主的检测，考虑到鸟巢附近明显的男性外观的鸡蛋排斥成本，它确实提供了匿名的好处。这些发现对整个Cuculidae的性二态性的进化和维持有意义，并强调了关于性二态性生态驱动因素的测试假设的价值。
