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

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合作寻找食物中受益，但它们也会招致更高的成本，例如对食物或配偶的竞争更激烈，更容易感染疾病和寄生虫。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。代价之一是配偶竞争的加剧，这可能导致性选择的增加。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，或者为另一种性别选择配偶。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，那么雄性之间的竞争也会在雌性的生殖道内发生。因此，我们不仅试图了解由性选择产生的外部特征（如孔雀的尾巴或大鹿角），而且还试图了解内部特征（如精子的速度）。由于单靠交配并不能保证受精，我们必须超越动物的行为来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、分子和内分泌技术的结合来检验关于独居和群居、自由放养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.