Sociality and reproductive tactics in ground-dwelling squirrels: conflict and cooperation

为什么有些动物是群居的，而有些动物不是，这是动物行为研究的一个主要领域。虽然群体中的个体可以从集体发现捕食者或帮助彼此抚养后代中受益，但它们也会带来更高的成本，比如争夺食物或配偶的竞争加剧，以及失去繁殖机会。我的研究项目侧重于通过研究这些成本和收益来理解社会性的演变。在复杂的动物社会中，雌性通常与近亲生活在一起，但这些近亲也是它们最亲密的竞争对手。在这样的群体中，繁殖并不是均匀分布的，成功与否往往取决于统治或侵略。在不使用侵略性资源竞争手段的平等主义社会中，即使我们观察到生殖成功率不平等，对影响生殖分布的因素所知较少。我们将测试与影响雌性繁殖成功的因素有关的假设，这些因素在一个似乎是平等的社会制度（所有成年动物都繁殖，没有统治等级）的物种中，但一些雌性比其他雌性断奶的后代多得多。雌性可能会争夺资源，而雄性则会通过性选择来争夺配偶。达尔文首先描述了性选择，包括一种性别直接竞争获得另一种性别的机会，或者一种性别选择配偶。这种竞争或选择可以导致适应，包括大鹿角和色彩鲜艳的羽毛。然而，如果一只雌性与不止一只雄性交配，那么竞争也会发生在雌性的生殖道中。因此，我们试图了解的不仅仅是性选择的可见结果（例如孔雀的尾巴），因为交配本身并不能确保受精。我们将研究精子和其他生殖结构在不同社会环境下的形态和功能的具体差异。了解男性精子形态和功能的差异可能是了解生殖成功的最终关键，但很少有研究调查这些差异。我们将使用行为学、分子学和内分泌学技术的结合，对独居和群居、自由放养的地松鼠，特别是群居的非洲地松鼠（Xerus inauris）的社会行为、繁殖和性选择的进化进行关键假设的检验。随着我们对20个分子标记的开发，我们可以确定这些非洲松鼠的详细遗传关系，我们正处于将这项研究过渡到一个新的理解水平的边缘。我们的研究结果将对进化生物学和生育研究具有理论和应用意义。

Why some animals are social and others are not is a major area of research in animal behaviour. Although individuals in groups can benefit from collective detection of predators or helping each other raise offspring, they also incur increased costs, such as more competition for food or mates and the loss of reproductive opportunities. My research program focuses on understanding the evolution of sociality by examining these costs and benefits. In complex animal societies, females usually live with their close kin but these close kin are also their closest competitors. Reproduction in such groups is not equally distributed and success is often determined by dominance or aggression. Less is known about the factors influencing reproductive distribution in egalitarian societies that do not use aggressive means of competing for resources, even when we observe unequal reproductive success. We will test hypotheses related to the factors that influence female reproductive success in a species with what appears to be an egalitarian social system (all adults breed and there is no dominance hierarchy), but where some females wean far more offspring than others. While females may compete for resources, males are predicted to compete for mates via sexual selection. First described by Darwin, sexual selection includes one sex directly competing to gain access to another or mate choice by one sex. Such competition or choice can lead to adaptations including large antlers and brightly coloured feathers. However, if a female mates with more than a single male, then competition can also occur in the reproductive tract of the female. Thus we seek to understand more than just the visible results of sexual selection (e.g. peacock's tail), as copulations alone do not ensure fertilization. We will examine specific differences in the morphology and functioning of sperm and other reproductive structures under different social situations. Understanding differences in sperm form and function among males may be the ultimate key to understanding reproductive success, yet few studies have investigated these differences. We will test critical hypotheses about the evolution of social behaviour, reproduction, and sexual selection in solitary and social, free-ranging ground squirrels, particularly the social African ground squirrel (Xerus inauris), using a combination of behavioural, molecular and endocrine techniques. With our development of 20 molecular markers that allow us to determine detailed genetic relationships in these African squirrels, we are on the edge of transitioning this research to a new level of understanding. Results of our research will have both theoretical and applied implications to evolutionary biology and fertility research.