Sociality and reproductive tactics in ground-dwelling squirrels: cooperation, tolerance and reproductive skew

生活史理论假设动物在生长、维持和繁殖方面的投资是有限的，并预测在一个特征上的投资将以另一个特征为代价(权衡)。繁殖和生存之间的权衡是一个主要的研究重点，特别是在具有缓慢(大身体，长寿)和快(小身体，短生命)生活史的物种之间。在不遵循通常模式的物种中研究这些权衡，以及在恶劣环境放大限制的物种中，将拓宽我们对生活史策略进化的理解。我的研究计划侧重于了解影响社会性和生殖策略演变的选择性力量。我们将使用行为学、分子和内分泌技术，在一只适应干旱的非洲黄鼠身上测试有关生活史、替代繁殖策略和合作繁殖的基本假设。我对这一物种的长期研究一直是检验社会复杂性的一个富有成效的系统，因为雌性是合作繁殖者，生活在有多个繁殖者的家庭群体中，而雄性生活在完全由雄性组成的群体中。雄性和雌性群体都是非领地的，没有统治等级，几乎没有攻击性(在哺乳动物中很少见)。它们虽然体型较小，但寿命很长，后代很少，与大型哺乳动物相似。雄性有两种选择--要么推迟离开并与家人呆在一起，要么分散加入全由男性组成的乐队。战术在繁殖成功方面没有差别，但每种战术的雄性后代中只有不到30%的人是这样的。我的项目关注的一个重点是研究男性的这种不对称的生殖成功、延迟的分散和寿命。在复杂的动物社会中，雌性通常与它们的近亲生活在一起，但这些近亲也是它们最接近的竞争对手。因此，社会性可以被视为队友之间合作与竞争之间的拉锯战。在雌性开普敦地松鼠中，大多数繁殖尝试都未能使后代断奶，但这种繁殖倾斜的原因尚不清楚。家庭内部的生育冲突并不明显，因此这种倾斜是意想不到的。在看似平等主义的家庭群体中测试与生活史和社会复杂性相关的假设是我的项目的第二个重点。合作繁殖，即个体照顾非自己的后代，通常被解释为帮助亲戚，但开普敦地松鼠的雄性照顾者提供照顾，作为一种租金形式。问题是，男性照顾者是否会增加繁殖者的生殖成功率或存活率？或者，育种者是否要为为其梳理毛发的男性护理者的感染买单？了解男性护理对女性的益处和成本是这项工作的另一个重点。这项研究的结果将对进化生物学以及人类和兽医学具有理论和应用意义，并将培训HQP在这些领域的关键实验室和现场工作技能。

Life-history theory assumes animals have finite energy to invest in growth, maintenance and reproduction and predicts that investment in one trait will come at a cost to another (trade-offs). The trade-off between reproduction and survival is a major focus of research, especially between species with slow (large-bodied, long-lived) and fast (small-bodied, short-lived) life histories. Examining these trade-offs in species that do not follow the usual patterns, and where harsh environments magnify constraints, will broaden our understanding of the evolution of life history strategies. My research program focuses on understanding the selective forces influencing the evolution of sociality and reproductive strategies. We will test fundamental hypotheses on life-history, alternative reproductive tactics and cooperative breeding in an arid-adapted African ground squirrel, using behavioural, molecular and endocrine techniques. My long-term study of this species has been a productive system for examining social complexity because females are cooperative breeders living in family groups with multiple breeders, and males live in all-male bands. Both male and female groups are non-territorial, lack dominance hierarchies and display little aggression (rare in mammals). They are long-lived, despite a small body size, and have few offspring, similar to a large mammal. Males have two alternative tactics - they either delay dispersal and stay with their family, or disperse and join all-male bands. Tactics do not differ in reproductive success but less than 30% of males of either tactic sire offspring. Examining this skewed reproductive success, delayed dispersal and longevity in males is one focus of my program. In complex animal societies, females usually live with their close kin but these close kin are also their closest competitors. Thus sociality can be seen as a tug-of-war between cooperation and competition among groupmates. In female Cape ground squirrels, most breeding attempts fail to wean offspring, but the reasons for this reproductive skew are unclear. Reproductive conflict within the family group is not apparent, so such skew is unexpected. Testing hypotheses related to life-history and social complexity in family groups that appear to be egalitarian is the second focus of my program. Cooperative breeding, where individuals care for offspring that are not their own, is usually explained as helping kin, but male carers in Cape ground squirrels provide care as a form of rent. The question is, do male carers increase the reproductive success or survival of breeders? Or do breeders pay the cost in terms of infections from grooming male carers? Understanding the benefits and costs of male care to females is another focus of this work. Results of this research will have theoretical and applied implications to evolutionary biology, and human and veterinary medicine, and will train HQP in crucial laboratory and fieldwork skills for these fields.