Davis Kathryn, Carlson P M, Bradley D, Warner R R, Caselle J E
Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, 93106, USA.
Marine Science Institute, University of California Santa Barbara, Santa Barbara, CA, 93106, USA.
Oecologia. 2017 May;184(1):139-149. doi: 10.1007/s00442-017-3857-9. Epub 2017 Mar 24.
In terrestrial systems it is well known that the spatial patterns of grazing by herbivores can influence the structure of primary producer communities. On coral reefs, the consequences of varied space use by herbivores on benthic community structure are not well understood, nor are the relative influences of bottom-up (resource abundance and quality), horizontal (competition), and top-down (predation risk) factors in affecting spatial foraging behaviors of mobile herbivorous fishes. In the current study we quantified space use and feeding rates of the parrotfish, Chlorurus spilurus, across a strong gradient of food resources and predator and competitor abundance across two islands with drastically different fisheries management schemes. We found evidence that while feeding rates of this species are affected by direct interference competition and chronic predation risk, space use appears to be primarily related to exploitative competition with the surrounding herbivore community. We found no evidence that predation risk influences diurnal foraging space use in this small bodied parrotfish species. Additionally, we found the influence of chronic predation risk on feeding rates of this species to be less dramatic than the results of recent studies that used model predators to measure acute behavioral responses of other species of herbivorous fishes. Our results indicate that the non-consumptive effects of predators on the foraging behaviors of coral reef herbivores may be less dramatic than previously thought.
在陆地系统中，食草动物的放牧空间模式会影响初级生产者群落的结构，这是众所周知的。在珊瑚礁上，食草动物不同的空间利用方式对底栖生物群落结构的影响尚未得到充分了解，影响游动食草鱼类空间觅食行为的自下而上（资源丰度和质量）、水平（竞争）和自上而下（捕食风险）因素的相对影响也不清楚。在本研究中，我们在两个渔业管理方案截然不同的岛屿上，量化了食物资源、捕食者和竞争者丰度梯度很大的情况下，斑鳍绿鹦嘴鱼（Chlorurus spilurus）的空间利用和摄食率。我们发现，虽然该物种的摄食率受直接干扰竞争和长期捕食风险的影响，但空间利用似乎主要与同周围食草动物群落的剥削性竞争有关。我们没有发现捕食风险会影响这种小型鹦嘴鱼的日间觅食空间利用的证据。此外，我们发现长期捕食风险对该物种摄食率的影响不如最近使用模型捕食者来测量其他食草鱼类急性行为反应的研究所得到的结果那么显著。我们的结果表明，捕食者对珊瑚礁食草动物觅食行为的非消费性影响可能比之前认为的要小。
