Department of Ethology, Eötvös Loránd University, Budapest, Hungary.
J Evol Biol. 2011 Aug;24(8):1842-6. doi: 10.1111/j.1420-9101.2011.02305.x.
In a number of insects, fishes and birds, the conventional sex roles are reversed: males are the main care provider, whereas females focus on matings. The reversal of typical sex roles is an evolutionary puzzle, because it challenges the foundations of sex roles, sexual selection and parental investment theory. Recent theoretical models predict that biased parental care may be a response to biased adult sex ratios (ASRs). However, estimating ASR is challenging in natural populations, because males and females often have different detectabilities. Here, we use demographic modelling with field data from 2101 individuals, including 579 molecularly sexed offspring, to provide evidence that ASR is strongly male biased in a polyandrous bird with male-biased care. The model predicts 6.1 times more adult males than females (ASR=0.860, proportion of males) in the Kentish plover Charadrius alexandrinus. The extreme male bias is consistent between years and concordant with experimental results showing strongly biased mating opportunity towards females. Based on these results, we conjecture that parental sex-role reversal may occur in populations that exhibit extreme male-biased ASR.
在一些昆虫、鱼类和鸟类中，传统的性别角色是颠倒的：雄性是主要的照顾者，而雌性则专注于交配。典型性别角色的颠倒，是一个进化难题，因为它挑战了性别角色、性选择和亲代投资理论的基础。最近的理论模型预测，有偏差的亲代照顾可能是对有偏差的成年性别比例（ASR）的一种反应。然而，在自然种群中估计 ASR 具有挑战性，因为雄性和雌性通常具有不同的可检测性。在这里，我们使用包括 579 个分子性别鉴定的后代在内的 2101 个个体的现场数据进行人口统计建模，为 ASR 在具有雄性偏爱的照顾的多配偶鸟类中强烈偏向雄性提供了证据。该模型预测，在蛎鹬 Charadrius alexandrinus 中，成年雄性比成年雌性多 6.1 倍（ASR=0.860，雄性比例）。这种极端的雄性偏向在各年份之间是一致的，并且与实验结果一致，实验结果表明，雌性的交配机会存在强烈的偏向。基于这些结果，我们推测，在表现出极端雄性偏向 ASR 的种群中，可能会发生亲代性别角色颠倒。
