Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird
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DOI：
10.1371/journal.pone.0028809
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发表时间：
2011-12-15
期刊：
影响因子：
3.7
通讯作者：
Cockburn, Andrew
中科院分区：
文献类型：
--
作者：
Calhim, Sara;Double, Michael C.;Cockburn, Andrew
交配后性选择是生殖性状进化的重要力量，包括精子形态。在鸟类中，精子形态是高度遗传的，并且在很大程度上不依赖于条件。理论预测，最近的比较工作证实，在这些性状的强选择减少种内表型变异。在这里，我们表明，一些变化可以保持尽管极端滥交，作为一个结果，相反的，交配角色特定的选择力量。在控制了已知的极好的细尾鹪鹩（Malurus cyaneus）的父系成功的相关因素后，我们发现：（a）终生的额外配对父系成功与精子具有较短的鞭毛和相对较大的头部有关，（B）精子具有较长的鞭毛和相对较小的头部的雄性获得较高的配对父系。在这个物种extrapair交配发生在同一个早晨，但之前，对交配在女性的生育期，这表明，较短和相对较大的头部精子是最成功的安全存储（防御），而相反的表型可能是更好地竞争存储精子（进攻）。此外，由于戴绿帽子的能力是一个主要的贡献者差异男性生殖输出，更强的选择防御精子竞争性状可能解释短的精子malurids相对于其他滥交雀形目。
Postcopulatory sexual selection is an important force in the evolution of reproductive traits, including sperm morphology. In birds, sperm morphology is known to be highly heritable and largely condition-independent. Theory predicts, and recent comparative work corroborates, that strong selection in such traits reduces intraspecific phenotypic variation. Here we show that some variation can be maintained despite extreme promiscuity, as a result of opposing, copulation-role-specific selection forces. After controlling for known correlates of siring success in the superb fairy-wren (Malurus cyaneus), we found that (a) lifetime extra-pair paternity success was associated with sperm with a shorter flagellum and relatively large head, and (b) males whose sperm had a longer flagellum and a relatively smaller head achieved higher within-pair paternity. In this species extrapair copulations occur in the same morning, but preceding, pair copulations during a female's fertile period, suggesting that shorter and relatively larger-headed sperm are most successful in securing storage (defense), whereas the opposite phenotype might be better at outcompeting stored sperm (offense). Furthermore, since cuckolding ability is a major contributor to differential male reproductive output, stronger selection on defense sperm competition traits might explain the short sperm of malurids relative to other promiscuous passerines.