Hierarchical density dependence in large animal ecology and evolution

从熊到马再到人，大型哺乳动物等长寿物种的生命史的主要驱动力是竞争，这种竞争往往随着人口规模（或密度）的增加而加剧。对我来说，除了密度依赖性之外，这些物种的生态学和进化几乎没有什么意义。我逐渐认识到密度依赖是一个生态学的等级过程。我的预测之一是，在给定的空间（从树叶到景观）和时间（从分钟到千年），种群的密度依赖性限制因素，如竞争、捕食、寄生甚至互利主义，将与适应度的代理（从能量到灭绝）相匹配。结论是，同一物种成员的承载力（K）的定义是规模依赖的。我相信这是非常重要的，因为每个有机体都是环境的“观察者”，生活史的适应可以改变感知尺度。这也意味着研究人员在我们如何解释密度相关动态的原因和后果并将我们的结果应用于保护方面发挥了作用。虽然正式理论的层次密度依赖是我的长期目标之一，我的计划的短期目标涉及到密度依赖的过程中出现的几个尺度和水平的生态组织的自由放养的马在紫貂岛国家公园储备，新斯科舍省。2007年开始，我对马进行了长期的、以个体为基础的研究，最近已经成熟：追踪了1385个马的生活史，它现在是世界上同类研究中最大的研究之一。在最近的进展，在文献中提出有趣的假设，但也利用目前的生态条件下的黑貂岛，我地址的规模和密度依赖的过程：（1）行为，包括在高密度带凝聚力的好处;什么决定带的大小;和密度和性别比例的影响，对马交配系统;（2）生活史特征，如对寄生反应的生育间隔的延长：（3）景观遗传学和近亲繁殖衰退的密度依赖;（4）马的K如何以及为什么会在空间和时间上从海洋到海洋发生变化，陆地营养转移和海洋营养级联，已经强大到足以反弹出海洋和塞布尔岛;（5）岛屿地理学以及如何从密度依赖的竞争和灭绝过程的平衡来决定岛屿上脊椎动物的体型进化。我的短期目标都具有培养不同背景的高素质学生的特殊潜力，导致突破性的进步，这是显着的，因为每个突出的目标针对不同层次的生态组织。因此，潜在的影响既广泛又深刻。这说明了将密度依赖的层次观点应用于生态学和进化的力量。

A principal driver of the life histories of long-lived species like large mammals, from bears to horses to people, has been competition which tends to intensify as population size (or density) increases. To me, little about the ecology and evolution of these species can really make sense except in the light of density dependence. I have come to know density dependence as a hierarchical process of ecology. One of my predictions is that density-dependent limiting factors to a population-like competition, predation, parasitism, or even mutualism-at a given space (leaf to landscape) and time (minutes to millenia) will match with proxies of fitness (energetics to extinction). The conclusion is that the very definition of carrying capacity (K) for members of the same species is scale dependent. I believe this to be of great significance as each organism is an `observer' of the environment and life-history adaptations can alter perceptual scales. It also means that there is a role for researchers in how we interpret the causes and consequences of density-related dynamics and apply our results to conservation. While formalizing theory on hierarchical density dependence is one of my long-term goals, the short-term goals of my program relate to density-dependent processes emerging across several scales and levels of ecological organization for the free-ranging horses at Sable Island National Park Reserve, Nova Scotia. Launched in 2007, my long-term, individual-based study of the horses has recently come of age: with 1385 life histories tracked it is now one of the world's largest studies of its kind. Building on recent advances in the literature to ask interesting hypotheses but also take advantage of current ecological conditions on Sable Island, I address scale- and density-dependent process regarding: (1) behaviour, including benefits of band cohesion at high density; what determines band size; and density- and sex-ratio impacts on the horse mating system; (2) life history traits like extension of the interbirth interval in response to parasitism; (3) landscape genetics and density-dependence of inbreeding depression; (4) how and why K for horses might vary in space and time from sea-to-land nutrient transfers and a marine trophic cascade that has been strong enough to bounce out of the ocean and onto Sable Island; and (5) island biogeography and how body size evolution of vertebrates on islands might be determined from the balance of density-dependent competition and extinction processes. My short-term goals all have exceptional potential to train high-calibre students of a diversity of backgrounds, leading to ground-breaking advances which is remarkable as each highlighted objective targets a different level of ecological organization. Potential impact is thus both broad-based and deep. This speaks to the power of applying a hierarchical perspective of density dependence to ecology and evolution.