Chakarov Nayden, Pauli Martina, Mueller Anna-Katharina, Potiek Astrid, Grünkorn Thomas, Dijkstra Cor, Krüger Oliver
Department of Animal Behaviour, Bielefeld University, PO Box 10 01 31, 33501, Bielefeld, Germany.
BioConsult SH, Brinckmannstr. 31, 25813, Husum, Germany.
PLoS One. 2015 Oct 7;10(10):e0138295. doi: 10.1371/journal.pone.0138295. eCollection 2015.
Parents may adapt their offspring sex ratio in response to their own phenotype and environmental conditions. The most significant causes for adaptive sex-ratio variation might express themselves as different distributions of fitness components between sexes along a given variable. Several causes for differential sex allocation in raptors with reversed sexual size dimorphism have been suggested. We search for correlates of fledgling sex in an extensive dataset on common buzzards Buteo buteo, a long-lived bird of prey. Larger female offspring could be more resource-demanding and starvation-prone and thus the costly sex. Prominent factors such as brood size and laying date did not predict nestling sex. Nonetheless, lifetime sex ratio (LSR, potentially indicative of individual sex allocation constraints) and overall nestling sex were explained by territory quality with more females being produced in better territories. Additionally, parental plumage morphs and the interaction of morph and prey abundance tended to explain LSR and nestling sex, indicating local adaptation of sex allocation However, in a limited census of nestling mortality, not females but males tended to die more frequently in prey-rich years. Also, although females could have potentially longer reproductive careers, a subset of our data encompassing full individual life histories showed that longevity and lifetime reproductive success were similarly distributed between the sexes. Thus, a basis for adaptive sex allocation in this population remains elusive. Overall, in common buzzards most major determinants of reproductive success appeared to have no effect on sex ratio but sex allocation may be adapted to local conditions in morph-specific patterns.
父母可能会根据自身表型和环境条件来调整后代的性别比例。适应性性别比例变化的最重要原因可能表现为在给定变量下两性之间适合度成分的不同分布。对于具有性大小二态性逆转的猛禽中性别分配差异的原因，已经提出了几种。我们在一个关于普通鵟（Buteo buteo）的广泛数据集中寻找雏鸟性别的相关因素，普通鵟是一种长寿的猛禽。体型较大的雌性后代可能对资源的需求更大且更容易挨饿，因此是成本较高的性别。诸如窝卵数和产卵日期等突出因素并不能预测雏鸟的性别。尽管如此，终生性别比例（LSR，可能指示个体性别分配限制）和总体雏鸟性别可以由领地质量来解释，在更好的领地中会产出更多雌性。此外，亲鸟的羽毛形态以及形态与猎物丰度的相互作用倾向于解释LSR和雏鸟性别，这表明性别分配存在局部适应性。然而，在对雏鸟死亡率的有限普查中，在猎物丰富的年份里，死亡更频繁的不是雌性而是雄性。而且，尽管雌性可能有潜在更长的繁殖生涯，但我们数据中包含完整个体生命史的一个子集表明，寿命和终生繁殖成功率在两性之间的分布相似。因此，该种群中适应性性别分配的基础仍然难以捉摸。总体而言，在普通鵟中，生殖成功的大多数主要决定因素似乎对性别比例没有影响，但性别分配可能以形态特异性模式适应当地条件。
