Spatial variation in the density of ectotherms

在物种内部，丰度（种群密度）在空间和时间上有显著变化。因此，解释物种丰度的时空格局是生态学的主要目标之一。丰富中心假说认为物种在其地理范围的中心附近最丰富，但经验数据并不支持这一假说。因此，我们显然需要另一种假设来更好地预测动物丰度的空间格局。******预测动物丰度的空间格局具有重要的理论和应用意义。在理论方面，更好地预测丰度的空间模式可能有助于确定是什么驱动了生物多样性的广泛空间模式。在应用方面，更好的预测空间格局的能力将有助于确定濒危物种的关键栖息地。******广泛空间尺度上的丰度主要由气候决定。然而，在物种的地理范围内，生境选择可以强烈地影响个体的分布和丰度。资源分布的空间异质性为生物通过选择最高质量的栖息地来最大化其适应性提供了机会。栖息地的适宜性是由占据栖息地的个体的平均成功率决定的，并取决于诸如食物丰度、住所可用性和竞争对手密度等因素。******大部分的栖息地选择理论都假定动物受到它们获取有限资源的能力的限制。但如果动物处理资源的能力受到限制，会发生什么呢？大多数动物都是变温动物，在变温动物中，可用能量的总量可能更强烈地受到资源同化的热约束而不是资源获取的影响。我的工作假设是，变温动物丰富的主要驱动力是它们处理资源的能力，而不是获取资源的能力。******我的研究计划的长期目标是确定是什么决定了变温动物丰度的空间模式。为了实现这一目标，我记录了空间中丰富的模式，并测试了关于产生这些空间模式的机制的假设。在下一个拨款周期，我的目标是确定是获取资源的能力，还是处理资源的能力，最能预测变温动物的丰度。我将在三个空间尺度上解决这个问题：在地理范围的尺度上（在范围内的丰度变化），在景观的尺度上（在栖息地梯度上的丰度变化），以及在个体家庭范围的尺度上（在质量不同的家庭范围之间的适合度变化）。

Within species, abundance (population density) varies markedly in space and in time. Accordingly, explaining spatial and temporal patterns in the abundance of species is one of the major goals of ecology. The abundant center hypothesis posits that species should be most abundant near the center of their geographic ranges, but the empirical data do not support it. Thus, there is a clear need for alternative hypotheses to predict better the spatial patterns in the abundance of animals.******Predicting spatial patterns in the abundance of animals has important theoretical and applied implications. On the theoretical side, a better prediction of spatial patterns in abundance may help determine what drives broad spatial patterns in biodiversity. On the applied side, a better ability to predict spatial patterns will help define critical habitats for species at risk.******Abundance at broad spatial scales is largely dictated by climate. Within the geographical range of species, however, habitat selection can strongly influence the distribution and abundance of individuals. The spatial heterogeneity of resource distribution provides an opportunity for organisms to maximize their fitness by choosing the highest quality habitat available. The suitability of a habitat is determined by the mean success rate of individuals that occupy the habitat, and depends on factors such as food abundance, shelter availability, and density of competitors.******Much of the habitat selection theory assumes that animals are limited by their ability to harvest limited resources. But what happens if animals are limited by their ability to process resources? Most animals are ectotherms, and in ectotherms the total amount of energy available may be more strongly influenced by thermal constraints on resource assimilation than by resource acquisition. My working hypothesis is that the primary driver of abundance in ectotherms is their ability to process resources, not their ability to acquire resources.******The long-term objective of my research program is to determine what dictates spatial patterns of abundance in ectotherms. To meet this objective, I document patterns of abundance in space and I test hypotheses about mechanisms that could generate these spatial patterns. My objective over the next grant cycle is to determine whether it is the ability to acquire, or the ability to process, resources that best predicts abundance of ectotherms. I will address this objective at three spatial scales: at the scale of the geographical range (variation in abundance across the range), at the scale of the landscape (variation in abundance across habitat gradients), and at the scale of the individual home ranges (variation in fitness between home ranges varying in quality).