Sexual Selection in Caring Parents: A Male and Female Perspective

交配后的父母照料在各个分类群中都很常见，但每个父母参与照料的程度差别很大。最初的理论认为，照顾应该偏向女性，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，而雄性通过投资寻找更多的配偶来最大化自己的健康，而不是提供照顾。这一观点在哺乳动物中似乎得到了强烈的经验支持，因为在哺乳动物中，只照顾雌性是最常见的照顾策略，但在其他分类学群体中，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，只有雄性照顾的情况很普遍。随后的理论表明，其他因素可能会对父母的策略产生更大的影响。性别比例会影响性伴侣的可获得性，从而影响护理的成本和收益，而不是寻找配偶。此外，女性的多次交配导致男性亲子关系保障的减少，减少了照顾男性的好处。更好地理解父母照料策略中涉及的权衡和性选择的作用对于研究形态、生态和生活史上的性别差异具有深远的好处，但尽管有广泛的理论和实证工作，创造观察到的父母策略多样性的过程仍然不清楚。在这个博士项目中，我将使用实验和比较的方法来调查两个未被研究的父系投资领域：a)在鱼类中父系照顾的性别选择；b)在繁殖的雌性中为质量信号进行选择。a)在鱼类中的雄性系：过去几十年来，对驱动鱼类父系系照顾的因素的实验工作有所增加，但对于为什么这种策略在这一群体中的物种中如此普遍还缺乏结论。我将使用对鱼类物种的荟萃分析来探索性选择，尤其是雌性对照料的选择，可能有助于推动这种不同寻常的模式。b)雌性照顾和质量信号：雌性和雄性一样，很可能被选中通过信号来宣传自己的生殖质量，但雌性在生殖方面的投资也比雄性更大，因此面临着这两种投资之间更大的权衡。利用实验室中对非洲叶蝉物种Lamprologus ocellatus的实验工作，我将研究在性内竞争繁殖资源期间的这种权衡。此外，我将在鸟类中进行比较分析，收集羽毛颜色的数据，结合生活史数据，了解雌性如何使用持续繁殖的信号来吸引合作繁殖物种的助手，以及这可能如何影响对护理的投资。

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.