R code from Mobility and its sensitivity to fitness differences determine consumer–resource distributions

An animal's movement rate (mobility) and its ability to perceive fitness gradients (fitness sensitivity) determine how well it can exploit resources. Previous models have examined mobility and fitness sensitivity separately and found that mobility, modelled as random movement, prevents animals from staying in high-quality patches, leading to a departure from an ideal free distribution (IFD). However, empirical work shows that animals with higher mobility can more effectively collect environmental information and better sense patch quality, especially when the environment is frequently changed by human activities. Here, we model, for the first time, this positive correlation between mobility and fitness sensitivity and measure its consequences for the populations of a consumer and its resource. In the absence of consumer demography, mobility alone had no effect on system equilibria, but a positive correlation between mobility and fitness sensitivity could produce an IFD. In the presence of consumer demography, lower levels of mobility prevented the system from approaching an IFD due to the mixing of consumers between patches. However, when positively correlated with fitness sensitivity, high mobility led to an IFD. Our study demonstrates that the expected covariation of animal movement attributes can drive broadly theorized consumer–resource patterns across space and time and could underlie the role of consumers in driving spatial heterogeneity in resource abundance.

动物的移动速率（mobility）以及其感知适合度梯度的能力（适合度敏感性，fitness sensitivity），共同决定了其开发资源的效率优劣。过往研究均单独考察移动速率与适合度敏感性，结果显示，被建模为随机移动的移动速率会阻碍动物停留在高质量生境斑块中，致使其偏离理想自由分布（ideal free distribution，IFD）。但实证研究表明，移动能力更强的动物能更高效地收集环境信息，也能更精准地判别斑块质量，在人类活动频繁改变环境的场景下这一现象尤为显著。
本研究首次针对移动速率与适合度敏感性之间的正相关关系开展建模，并量化该关系对消费者及其资源种群的影响。在不考虑消费者种群动态的前提下，仅移动速率对系统均衡状态无显著影响，但移动速率与适合度敏感性的正相关关系可催生理想自由分布。当纳入消费者种群动态后，较低的移动速率会因不同斑块间消费者的混合作用，阻碍系统趋近理想自由分布；但当移动速率与适合度敏感性呈正相关时，高移动速率可推动系统达成理想自由分布。
本研究证实，动物移动属性的预期协变关系，能够驱动理论中广泛存在的消费者-资源时空分布模式，或可成为消费者驱动资源丰度空间异质性的核心机制。