Fitness consequences of habitat selection in terrestrial ectotherms

在物种内部，个体的丰度在空间上是不同的。地理范围是丰度的函数：它的界限是在人口密度下降到零的地方。种群平均适应度主要是当地个体生存和繁殖的函数，它们共同决定了种群的平均适应度。因此，丰度的空间变异模式与种群平均适合度的空间变异模式密切相关。在脊椎动物中，有大量的论文描述了栖息地的使用，但令人惊讶的是，很少有人解决量化栖息地选择的适应性后果的核心问题。陆生变温脊椎动物提供了一个独特的机会，以弥合栖息地利用和健身之间的差距，因为它们的有机体性能随体温而变化，这在很大程度上是通过栖息地选择调节。因此，我们在这个群体的栖息地利用和适合度之间存在明确的机械联系。大部分的栖息地选择理论都是在考虑脊椎动物恒温动物的情况下发展起来的，并假设动物受到它们获取资源的能力的限制。但是，如果动物不受它们获取资源的能力的限制，而是受它们处理资源的能力的限制，会发生什么呢？大多数脊椎动物是外温动物，在外温动物中，利用的能量总量可能更强烈地受到资源获取和同化的热约束的影响，而不是资源的可用性。我的工作假设在这个建议是，相反的脊椎动物的恒温动物，在陆生脊椎动物的外温动物种群平均健身的主要驱动力是他们的能力，处理资源，而不是他们的能力，以获取资源。这一假设可以在物种范围尺度（物种地理范围内的种群平均适合度的变化），景观尺度（温度和资源可用性不同的当地地点的种群平均适合度的变化），或在个人尺度（个人适合度的变化作为家庭范围内的热质量和资源可用性的函数）。我建议在所有3个空间尺度进行测试，使用相关和操纵蜥蜴的实地研究。

Within species, the abundance of individuals varies in space. The geographic range is a function of abundance: its limits are set where population density declines to zero. Abundance is largely a function of local individual survival and reproduction, which together dictate population mean fitness. Therefore, the pattern of spatial variation in abundance is intimately tied to the pattern of spatial variation in population mean fitness. In vertebrates there is a plethora of papers describing habitat use, but surprisingly few tackle the central issue of quantifying the fitness consequences of habitat selection. Terrestrial ectothermic vertebrates offer a unique opportunity to bridge the gap between habitat use and fitness because their organismal performance varies with body temperature which is regulated largely via habitat selection. We thus have an explicit mechanistic link between habitat use and fitness in this group. Much of the habitat selection theory has been developed with vertebrate endotherms in mind and assumes that animals are limited by their ability to harvest resources. But what happens if animals are not limited by their ability to harvest resources, but rather by their ability to process resources? Most vertebrates are ectotherms, and in ectotherms the total amount of energy utilized may be more strongly influenced by thermal constraints on resource acquisition and assimilation than by resource availability. My working hypothesis in this proposal is that, contrary to vertebrate endotherms, the primary driver of population mean fitness in terrestrial vertebrate ectotherms is their ability to process resources, not their ability to acquire resources. This hypothesis can be operationalized at the species range scale (variation in population mean fitness across the geographic range of species), at the landscape scale (variation in population mean fitness across local sites that vary in temperature and resource availability), or at the individual scale (variation in individual fitness as a function of the thermal quality and resource availability within the home range). I propose to conduct tests at all 3 spatial scales using correlative and manipulative field studies of lizards.