Sexual Selection in Caring Parents: A Male and Female Perspective

交配后亲代抚育在整个分类群中很常见，但每个亲代参与抚育的程度差别很大。最初的理论认为，照顾应该偏向于雌性，因为雌性通过卵子和受精卵对后代进行了更大的初始投资，而雄性则有能力通过投资寻找额外的配偶来最大化自己的适应性，而不是提供照顾。这一观点在哺乳动物中得到了强有力的实证支持，在哺乳动物中，只有雌性照顾是最常见的照顾策略，但在其他分类群体中，情况并非如此。在鸟类中，超过90%的物种表现出双亲照顾，而在鱼类中，只有雄性照顾是普遍的。随后的理论表明，其他因素可能对父母的策略有更大的影响。性别比例影响性伴侣的可获得性，从而影响照顾配偶与寻找配偶的成本和收益。此外，雌性的多次交配导致雄性父权保证的减少，减少了照顾雄性的好处。更好地理解亲代抚育策略和性选择的权衡关系，对形态学、生态学和生活史上的性别差异研究具有深远的意义。但是，尽管进行了广泛的理论和实证研究，但观察到亲代抚育策略多样性的形成过程仍不清楚。在这个博士项目中，我将使用实验和比较的方法来研究亲代投资的两个尚未得到充分研究的领域：a)鱼类父系照顾的性选择b)繁殖雌性质量信号的选择。a)鱼类中的雄性关怀：在过去的几十年里，对鱼类中驱动雄性关怀的因素的实验工作有所增加，但关于为什么这种策略在该群体中如此普遍的结论却缺乏。我将使用跨鱼类的荟萃分析来探索性选择，特别是雌性对照顾的选择，是如何帮助推动这种不寻常的模式的。b)雌性关爱和质量信号：雌性和雄性一样，很可能被选择通过信号来宣传自己的生殖质量，但雌性在繁殖方面的投入也比雄性多，因此在这两种投资之间面临着更大的权衡。我将利用实验室对非洲慈鲷的实验工作，研究交配资源竞争过程中的这种权衡。此外，我将对鸟类进行比较分析，收集羽毛颜色的数据，结合生活史数据，以了解在合作繁殖的物种中，雌性如何使用持续繁殖力的信号来吸引帮手，以及这可能如何影响照顾的投资。

Post-mating parental care is common across taxa, yet the degree to which each parent is involved in care varies widely. Original theory suggests that care should be female-biased due to females' greater initial investment in offspring through eggs and zygotes and males' ability to maximise their fitness by investing in seeking additional mates over providing care. Empirical support for this idea appears strong in mammals where female-only care is the most common care strategy, but in other taxonomic groups this is not the case. In birds, more than 90% of species exhibit biparental care, and in fish, male-only care is prevalent. Subsequent theory has shown that other factors could have a greater influence on parental strategy. Sex ratios influence the availability of sexual partners thereby affecting the costs and benefits of care versus mate searching. Additionally, multiple mating by females leads to decreases in male paternity assurance decreasing the benefits of care to males. A greater understanding of the trade-offs involved in parental care strategies and the role of sexual selection has far-reaching benefits for the study of sex differences in morphology, ecology and life history but, despite extensive theoretical and empirical work, the processes involved in creating the observed diversity of parental strategies remain unclear.During this PhD project, I will use experimental and comparative methods to investigate two understudied areas of parental investment: a) sexual selection for paternal care in fish b) selection for quality signalling in breeding females.a) Male care in fish:Experimental work into the factors that drive paternal care in fish has increased in the last few decades yet conclusions about why this strategy is so common across species in this group are lacking. I will use meta-analysis across fish species to explore how sexual selection, particularly female-choice for care, may have helped to drive this unusual pattern.b) Female care and quality signalling:Females, like males, are likely to be selected to advertise their reproductive quality through signalling, yet females also invest more heavily in reproduction than males and so face a greater trade-off between these two investments. Using experimental work in the laboratory on the African cichlid species Lamprologus ocellatus, I will investigate this trade-off during intra-sexual competition for breeding resources.In addition, I will undertake a comparative analysis in birds, collecting data on plumage coloration combined with life-history data to understand how females may use signals of continuing fecundity to attract helpers in cooperatively breeding species and how this may influence investment in care.