Department of Environmental Science & Policy, University of California, One Shields Avenue, Davis, California, 95616, USA.
Department of Biology, University of Florida, 220 Bartram Hall, PO Box 118525, Gainesville, Florida, 32611, USA.
Ecology. 2017 Feb;98(2):534-544. doi: 10.1002/ecy.1668. Epub 2017 Jan 12.
Foraging theory posits that isolation from refuge habitat within a landscape increases perceived predation risk and, thus, suppresses the foraging behavior of prey species. However, these effects may depend fundamentally on resource availability, which could affect prey boldness and can change considerably through bottom-up processes. We conducted a field survey and experiment in a coral reef to test the effects of isolation from refuge habitat (i.e., reef structure) on herbivory by reef fishes and whether these effects depend on resource density. By fitting continuous-time, pure death Markov processes to our data, we found that at both the local and landscape scale distance from refuge habitat reduced herbivory in attractive resource patches of palatable benthic algae. However, our field experiment revealed that higher initial resource densities weakened negative effects of distance from refuge habitat on herbivory. Furthermore, we observed higher bite rates and greater total lengths of herbivorous fishes with greater distance from refuge habitat-responses consistent with higher perceived predation risk. Our results suggest that while the loss or fragmentation of refuge habitat reduces consumer control of resources, greater resource densities can partially counteract this effect by altering landscapes of fear of consumer species. Our findings emphasize the importance of considering the spatial context of species interactions that structure communities.
觅食理论认为，在景观中与避难栖息地隔离会增加被捕食的风险，从而抑制猎物物种的觅食行为。然而，这些影响可能从根本上取决于资源的可利用性，这可能会影响猎物的大胆程度，并通过自下而上的过程发生相当大的变化。我们在珊瑚礁中进行了一项实地调查和实验，以测试与避难栖息地（即珊瑚礁结构）隔离对珊瑚礁鱼类食草行为的影响，以及这些影响是否取决于资源密度。通过将连续时间、纯死亡马尔可夫过程拟合到我们的数据中，我们发现，在局部和景观尺度上，距离避难栖息地越远，有吸引力的底栖藻类的食草行为就越少。然而，我们的实地实验表明，较高的初始资源密度会削弱距离避难栖息地对食草作用的负面影响。此外，我们观察到与避难栖息地的距离越大，食草鱼类的咬噬率越高，总长度越大，这与更高的被捕食风险感知一致。我们的研究结果表明，虽然避难栖息地的丧失或碎片化会降低消费者对资源的控制，但通过改变消费者物种恐惧的景观，更大的资源密度可以部分抵消这种影响。我们的研究结果强调了考虑物种相互作用的空间背景对群落结构的重要性。
