Parasites favour intermediate nestling mass and brood size in cliff swallows
Parasites favour intermediate nestling mass and brood size in cliff swallows
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DOI：
10.1111/jeb.13218
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发表时间：
2018-02-01
影响因子：
2.1
通讯作者：
Brown, Mary Bomberger
中科院分区：
文献类型：
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作者：
Brown, Charles R.;Brown, Mary Bomberger
生活史理论的一个挑战是解释为什么动物的体型没有继续增长，因为更大的体型有各种优势。在鸟类中，雏鸟的身体大小和所产雏鸟的数量(雏鸟大小)有时被证明受到对较大雏鸟和来自较大雏鸟的较高捕食量的限制。众所周知，寄生虫对鸟类的生活史特征也有很大的影响，但寄生虫能否成为稳定选择雏鸟身体大小或雏鸟大小的驱动因素尚不清楚。我们研究了内布拉斯加州西部悬崖燕子(Petrochelidon Pyrhonota)在自然条件下和通过熏蒸清除食血性体外寄生虫的巢中，第一年的存活模式与巢中雏鸟大小和雏体质量的关系。来自寄生巢的鸟类在最常见的中等窝大小和雏群类别中表现出最高的第一年存活率，而来自非寄生巢的悬崖燕子在最重的巢群中表现出最高的存活率，与雏鸟大小无关。一项生存分析表明，在有寄生虫的情况下(但不是在没有寄生虫的情况下)，对雏鸟大小和雏鸟群体的选择是稳定的。寄生虫显然偏爱悬崖燕子的中间后代大小和数量，并产生观察到的这些特征的分布，尽管机制尚不清楚。我们的结果强调了寄生虫在生活史进化中的重要性。
A challenge of life-history theory is to explain why animal body size does not continue to increase, given various advantages of larger size. In birds, body size of nestlings and the number of nestlings produced (brood size) have occasionally been shown to be constrained by higher predation on larger nestlings and those from larger broods. Parasites also are known to have strong effects on life-history traits in birds, but whether parasitism can be a driver for stabilizing selection on nestling body size or brood size is unknown. We studied patterns of first-year survival in cliff swallows (Petrochelidon pyrrhonota) in western Nebraska in relation to brood size and nestling body mass in nests under natural conditions and in those in which hematophagous ectoparasites had been removed by fumigation. Birds from parasitized nests showed highest first-year survival at the most common, intermediate brood-size and nestling-mass categories, but cliff swallows from nonparasitized nests had highest survival at the heaviest nestling masses and no relationship with brood size. A survival analysis suggested stabilizing selection on brood size and nestling mass in the presence (but not in the absence) of parasites. Parasites apparently favour intermediate offspring size and number in cliff swallows and produce the observed distributions of these traits, although the mechanisms are unclear. Our results emphasize the importance of parasites in life-history evolution.