PT  - JOURNAL ARTICLE
AU  - Luke J. Eberhart-Phillips
AU  - Clemens Küpper
AU  - María Cristina Carmona-Isunza
AU  - Orsolya Vincze
AU  - Sama Zefania
AU  - Medardo Cruz-López
AU  - András Kosztolányi
AU  - Tom E. X. Miller
AU  - Zoltán Barta
AU  - Innes C. Cuthill
AU  - Terry Burke
AU  - Tamás Székely
AU  - Joseph I. Hoffman
AU  - Oliver Krüger
TI  - Demographic causes of adult sex ratio variation and their consequences for parental cooperation
AID  - 10.1101/223941
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 223941
4099  - http://biorxiv.org/content/early/2017/12/14/223941.short
4100  - http://biorxiv.org/content/early/2017/12/14/223941.full
AB  - The adult sex ratio (ASR) is a fundamental concept in population biology, sexual selection, and social evolution. However, it remains unclear which demographic processes generate ASR variation and how biases in ASR in turn affect social behaviour. Here, we evaluate the demographic mechanisms shaping ASR and their consequences for parental cooperation using detailed survival, fecundity, and behavioural data on 6,119 individuals from six wild shorebird populations exhibiting flexible parental strategies. We show that these closely related populations express strikingly different ASRs, despite having similar ecologies and life histories, and that ASR variation is largely driven by sex differences in the apparent survival of juveniles. Furthermore, families in populations with biased ASRs were predominantly tended by a single parent, suggesting that parental cooperation breaks down with unbalanced sex ratios. Taken together, our results indicate that sex biases emerging during early life have profound consequences for social behaviour.