PDF(Pubmed)
Abstract：
Egg rejection is an effective and widespread antiparasitic defense to eliminate foreign eggs from the nests of hosts of brood parasitic birds. Several lines of observational and critical experimental evidence support a role for learning by hosts in the recognition of parasitic versus own eggs; specifically, individual hosts that have had prior or current experience with brood parasitism are more likely to reject foreign eggs. Here we confirm experimentally the role of prior experience in altering subsequent egg-rejection decisions in the American robin Turdus migratorius, a free-living host species of an obligate brood parasite, the brown-headed cowbird Molothrus ater. We then model the coevolutionary trajectory of both the extent of mimicry of host eggs by parasitic eggs and the host\'s egg rejection thresholds in response to an increasing role of learning in egg recognition. Critically, with more learning, we see the evolution of both narrower (more discriminating) rejection thresholds in hosts and greater egg mimicry in parasites. Increasing host clutch size (number of eggs/nest) and increasing parasite load (parasitism rate) also have narrowing effects on the egg-rejection threshold. Together, these results suggest that learning from prior experience with egg rejection may play an important role in the coevolution of egg-mimetic lineages of brood parasites and the refined egg rejection defenses of hosts.
摘要：
卵排斥是一种有效且广泛的抗寄生虫防御措施，可从育巢寄生鸟类的寄主巢中消除外来卵。几条观察性和关键的实验证据支持宿主学习在识别寄生虫与自身卵方面的作用；特别是，以前或现在有过亲鱼寄生经历的个体宿主更有可能拒绝外来卵。在这里，我们通过实验证实了先前经验在改变美国知更鸟中随后的卵排斥决定中的作用。一种专性育幼寄生虫的自由生活宿主物种，棕色头的牛鸟Molothrus水。然后，我们对寄生卵对宿主卵的模仿程度和宿主卵排斥阈值的共同进化轨迹进行建模，以响应学习在卵识别中的作用越来越大。严重的,随着更多的学习，我们看到宿主中更窄（更具区别性）的排斥阈值和寄生虫中更大的卵拟态的演变。增加寄主的离合器大小（卵/巢的数量）和增加的寄生虫负荷（寄生率）也会对卵排斥阈值产生缩小的影响。一起,这些结果表明，从先前的卵排斥经验中学习可能在育卵寄生虫的卵模拟谱系和宿主的精制卵排斥防御的共同进化中起重要作用。
