Sociality and reproductive strategies in ground-dwelling squirrels: effects of infection on reproduction and sperm competition

为什么有些动物是社会性的，而有些不是，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合作寻找食物中受益，但他们也会增加成本，例如更多的食物或配偶竞争以及更多的疾病和寄生虫暴露。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。其中一个代价是，对配偶的竞争加剧，这会导致性选择的增加。首先由达尔文描述的是，性选择包括一种性别直接竞争以获得另一种性别的机会，或者一种性别为另一种性别选择配偶。这样的竞争或选择可以导致适应，包括大鹿角和鲜艳的羽毛。然而，如果一个雌性与一个以上的雄性交配，那么雄性之间的竞争也会发生在雌性的生殖道内。因此，我们不仅要了解性选择产生的外部特征（例如孔雀的尾巴或大鹿角），而且要了解内部特征（例如精子的速度）。 由于单靠交配并不能确保受精，我们必须超越动物的行为去观察它的精子的行为。我们将研究精子形态和功能的具体差异，以及个体对病原体和寄生虫的反应及其对生育能力的影响。了解男性精子形态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，分子和内分泌技术相结合的方法来测试关于孤独和社会，自由放养的地松鼠的社会行为和性选择进化的关键假设。我们的研究结果将对进化生物学和流行病学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 cooperative food searching, they also incur increased costs, such as more competition for food or mates and greater exposure to diseases and parasites. My research program focuses on understanding the evolution of sociality by examining these costs and benefits. One cost, increased competition for mates, can result in increased sexual selection. First described by Darwin, sexual selection includes one sex directly competing to gain access to the other or mate choice of one sex for the other. 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 male-male competition can also occur within the reproductive tract of the female. Thus we seek to understand not only external features resulting from sexual selection (e.g. peacock's tail or large antlers), but also internal (such as the speed of sperm). As copulations alone do not ensure fertilization we must look beyond the behaviour of the animal to the behaviour of his sperm. We will examine specific differences in the morphology and functioning of sperm, as well as the response of individuals to pathogens and parasites and effects on their fertility. Understanding differences in sperm morphology 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 and sexual selection in solitary and social, free-ranging ground squirrels using a combination of behavioural, molecular, and endocrine techniques. Results of our research will have both theoretical and applied implications to evolutionary biology and epidemiology.