Egg arrangement in avian clutches covaries with the rejection of foreign eggs
Egg arrangement in avian clutches covaries with the rejection of foreign eggs
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DOI：
10.1007/s10071-013-0615-1
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发表时间：
2013-02
期刊：
影响因子：
2.7
通讯作者：
Lenka Polačiková;F. Takasu;B. Stokke;A. Moksnes;E. Røskaft;P. Cassey;M. Hauber;T. Grim
中科院分区：
文献类型：
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作者：
Lenka Polačiková;F. Takasu;B. Stokke;A. Moksnes;E. Røskaft;P. Cassey;M. Hauber;T. Grim
对于鸟类来说，蛋的颜色、斑点、形状和大小对于辨别窝中的外来蛋起着至关重要的作用。然而，到目前为止，还没有研究检验一窝卵的排列对宿主排斥反应的作用。我们预测，与没有一致卵排列的雌性（即卵在孵化过程中更频繁地改变位置）相比，在其窝内保持一致卵排列的雌性个体能够更好地检测和拒绝外来卵。我们在黑鸫（Turdus merula）和画眉（T. philomelos）身上测试了这种“卵排列假说”。这两个物种都是卵子排斥研究的合适候选者，因为它们在卵子排斥反应中表现出较高的个体间差异和个体重复性。正如预测的那样，使用我们自定义的卵子排列指标，拒绝雌性的卵子排列显示出比接受性雌性的卵子排列更加一致的模式。只有与钝极相关的参数在拒绝者和接受者之间表现出一致的差异。这一发现具有生物学意义，因为众所周知，画眉使用钝杆线索来拒绝外来卵。我们认为，产蛋寄生虫对原始卵排列模式的干扰可能会提醒保持一致卵排列的雌性宿主有被寄生虫感染的风险。一旦收到警报，这些宿主可能会将其辨别阈值调整得更加严格，以便以更高的概率拒绝外国鸡蛋。未来的研究将受益于实验测试这两种和其他寄生排斥宿主物种是否可能依赖于使用一致的卵排列作为其抗寄生虫防御机制的组成部分。
In birds, the colour, maculation, shape, and size of their eggs play critical roles in discrimination of foreign eggs in the clutch. So far, however, no study has examined the role of egg arrangement within a clutch on host rejection responses. We predicted that individual females which maintain consistent egg arrangements within their clutch would be better able to detect and reject foreign eggs than females without a consistent egg arrangement (i.e. whose eggs change positions more often across incubation). We tested this “egg arrangement hypothesis” in blackbirds (Turdus merula) and song thrush (T. philomelos). Both species are suitable candidates for research on egg rejection, because they show high inter-individual variation and individual repeatability in egg rejection responses. As predicted, using our custom-defined metrics of egg arrangement, rejecter females’ clutches showed significantly more consistent patterns in egg arrangement than acceptor females’ clutches. Only parameters related to blunt pole showed consistent differences between rejecters and acceptors. This finding makes biological sense because it is already known that song thrush use blunt pole cues to reject foreign eggs. We propose that a disturbance of the original egg arrangement pattern by the laying parasite may alert host females that maintain a consistent egg arrangement to the risk of having been parasitized. Once alerted, these hosts may shift their discrimination thresholds to be more restrictive so as to reject a foreign egg with higher probability. Future studies will benefit from experimentally testing whether these two and other parasitized rejecter host species may rely on the use of consistent egg arrangements as a component of their anti-parasitic defence mechanisms.