Liker András, Freckleton Robert P, Remeš Vladimir, Székely Tamás
Department of Animal and Plant Sciences, Alfred Denny Building, University of Sheffield, Western Bank, Sheffield, S10 2TN, United Kingdom.
Department of Limnology, University of Pannonia, PO Box 158, 8201, Veszprém, Hungary.
Evolution. 2015 Nov;69(11):2862-75. doi: 10.1111/evo.12786. Epub 2015 Oct 13.
Male and female parents often provide different type and amount of care to their offspring. Three major drivers have been proposed to explain parental sex roles: (1) differential gametic investment by males and females that precipitates into sex difference in care, (2) different intensity of sexual selection acting on males and females, and (3) biased social environment that facilitates the more common sex to provide more care. Here, we provide the most comprehensive assessment of these hypotheses using detailed parental care data from 792 bird species covering 126 families. We found no evidence for the gametic investment hypothesis: neither gamete sizes nor gamete production by males relative to females was related to sex difference in parental care. However, sexual selection correlated with parental sex roles, because the male share in care relative to female decreased with both extra-pair paternity and frequency of male polygamy. Parental sex roles were also related to social environment, because male parental care increased with male-biased adult sex ratios (ASRs). Taken together, our results are consistent with recent theories suggesting that gametic investment is not tied to parental sex roles, and highlight the importance of both sexual selection and ASR in influencing parental sex roles.
雄性和雌性亲本通常会为其后代提供不同类型和数量的照料。人们提出了三个主要驱动因素来解释亲本性角色：（1）雄性和雌性配子投资的差异，这导致了照料方面的性别差异；（2）作用于雄性和雌性的性选择强度不同；（3）有偏向性的社会环境，这使得更为常见的性别提供更多照料。在此，我们利用涵盖126个科的792种鸟类的详细亲代照料数据，对这些假说进行了最全面的评估。我们没有找到支持配子投资假说的证据：无论是配子大小还是雄性相对于雌性的配子产量，都与亲代照料中的性别差异无关。然而，性选择与亲本性角色相关，因为相对于雌性而言，雄性在照料中的比例会随着婚外父权和雄性多配偶频率的增加而降低。亲本性角色也与社会环境有关，因为雄性亲代照料会随着雄性偏向的成年性别比（ASR）而增加。综合来看，我们的结果与最近的理论一致，即配子投资与亲本性角色无关，并突出了性选择和成年性别比在影响亲本性角色方面的重要性。
