Uller Tobias
School of Biological Sciences, University of Wollongong, NSW 2522, Australia.
Biol Rev Camb Philos Soc. 2006 May;81(2):207-17. doi: 10.1017/S1464793105006962.
Vertebrate sex ratios are notorious for their lack of fit to theoretical models, both with respect to the direction and the magnitude of the sex ratio adjustment. The reasons for this are likely to be linked to simplifying assumptions regarding vertebrate life histories. More specifically, if the sex ratio adjustment itself influences offspring fitness, due to sex-specific interactions among offspring, this could affect optimal sex ratios. A review of the literature suggests that sex-specific sibling interactions in vertebrates result from three major causes: (i) sex asymmetries in competitive ability, for example due to sexual dimorphism, (ii) sex-specific cooperation or helping, and (iii) sex asymmetries in non-competitive interactions, for example steroid leakage between fetuses. Incorporating sex-specific sibling interactions into a sex ratio model shows that they will affect maternal sex ratio strategies and, under some conditions, can repress other selection pressures for sex ratio adjustment. Furthermore, sex-specific interactions could also explain patterns of within-brood sex ratio (e.g. in relation to laying order). Failure to take sex-specific sibling interactions into account could partly explain the lack of sex ratio adjustment in accordance with theoretical expectations in vertebrates, and differences among taxa in sex-specific sibling interactions generate predictions for comparative and experimental studies.
脊椎动物的性别比例因其不符合理论模型而声名狼藉，无论是在性别比例调整的方向还是幅度方面。其原因可能与关于脊椎动物生活史的简化假设有关。更具体地说，如果性别比例调整本身由于后代之间特定性别的相互作用而影响后代的适应性，这可能会影响最优性别比例。对文献的回顾表明，脊椎动物中特定性别的同胞相互作用源于三个主要原因：（i）竞争能力的性别不对称，例如由于两性异形；（ii）特定性别的合作或帮助；（iii）非竞争性相互作用中的性别不对称，例如胎儿之间的类固醇泄漏。将特定性别的同胞相互作用纳入性别比例模型表明，它们将影响母体的性别比例策略，并且在某些情况下，可以抑制性别比例调整的其他选择压力。此外，特定性别的相互作用还可以解释窝内性别比例的模式（例如与产卵顺序有关）。未能考虑特定性别的同胞相互作用可能部分解释了脊椎动物中性别比例调整不符合理论预期的情况，并且不同分类群中特定性别的同胞相互作用差异为比较和实验研究产生了预测。
