Science2014-06-11 1:23 PM

寄生性杜鹃帮助它们的宿主乌鸦击退掠食敌人 From Parasitism to Mutualism: Unexpected Interactions Between a Cuckoo and Its Host

论文摘要 

一项为期16年的对大凤头鹃和食腐肉乌鸦的研究揭示了这些寄生性杜鹃也可通过击退掠食动物而帮助它们的宿主;大凤头鹃对食腐肉乌鸦来说是一种巢寄生鸟类(它们会将自己生的蛋偷偷置入食腐肉乌鸦的巢内)。这些发现提示,在寄生性、共生性和互惠性之间的界限并非如研究人员过去所认为的那样黑白分明;他们凸显了物种间的互动是如何依赖于环境因素的。

Daniela Canestrari及其同事对西班牙北部的食腐肉乌鸦巢进行了研究并发现,这些被外鸟寄生的乌鸦巢总体上要比其没有杜鹃蛋的对等乌鸦巢实际上更为成功;这些乌鸦巢中的某些被杜鹃蛋寄生,而另外一些则没有寄生的杜鹃蛋。

据研究人员披露,尽管这些寄生鸟确实限制了乌鸦在生殖方面的成功——因为寄生幼鸟会与其宿主自己生的幼鸟竞争食物,但杜鹃幼鸟同时也会保护这些乌鸦不受哺乳性掠食动物及其它鸟类的影响。

对化学物的一个分析显示,这些杜鹃鸟会分泌某种有毒物质——它们是一种主要为酸、吲哚、酚类及数种含硫化合物的腐蚀性与排斥性化合物的混合;该有毒物质可有效地驱赶半野生的猫及猛禽。当来自这类掠食动物的压力高涨时,这些鹃鸟可帮助增加该类乌鸦的种群数。


Abstract 

Avian brood parasites lay eggs in the nests of other birds, which raise the unrelated chicks and typically suffer partial or complete loss of their own brood. However, carrion crows Corvus corone corone can benefit from parasitism by the great spotted cuckoo Clamator glandarius. Parasitized nests have lower rates of predation-induced failure due to production of a repellent secretion by cuckoo chicks, but among nests that are successful, those with cuckoo chicks fledge fewer crows. The outcome of these counterbalancing effects fluctuates between parasitism and mutualism each season, depending on the intensity of predation pressure.

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