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.

Biodiversity Laboratory Department of Biology and Biochemistry University of Bath Bath BA2 7AY United Kingdom State Key Laboratory of Biocontrol College of Ecology and Evolution Sun Yat sen University Guangzhou 5102275 China

Department of Animal and Plant Sciences Alfred Denny Building University of Sheffield Western Bank Sheffield S10 2TN United Kingdom

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

Department of Zoology and Laboratory of Ornithology Palacký University 17 listopadu 50 77146 Olomouc Czech Republic

Citace poskytuje Crossref.org