Bell Johann D, Westoby Mark
School of Biological Sciences, Macquarie University, 2113, North Ryde, N.S.W., Australia.
Department of Agriculture, Fisheries Research Institute, P.O. Box K220, 2000, Haymarket, N.S.W., Australia.
Oecologia. 1986 Jan;68(2):205-209. doi: 10.1007/BF00384788.
Two main hypotheses compete to explain why prey abundance decreases when seagrass density is reduced. One proposes that predators are more successful amongst seagrass of lower density; the other invokes habitat choice by prey. We reduced the density of seagrass in the presence, and in the absence, of predators in a field experiment to discriminate between these hypotheses. When seagrass was manipulated abundances of all six prey species decreased simultaneously both in the presence and in the absence of predators. We conclude that correlations of prey abundance and shoot density within a seagrass bed are proximately due to habitat preference of dense seagrass by prey. We report another experiment which supports this conclusion and shows that habitat preference is exercised at the earliest opportunity. However, the habitat preferences may have been selected by predation pressure.
关于为何海草密度降低时猎物数量会减少，有两种主要假说相互竞争以做出解释。一种假说认为，在密度较低的海草中，捕食者的成功率更高；另一种假说则认为是猎物进行了栖息地选择。我们在野外实验中，分别在有捕食者和无捕食者的情况下降低海草密度，以区分这两种假说。当对海草进行操控时，无论有无捕食者，所有六种猎物的数量都同时减少。我们得出结论，海草床内猎物数量与海草茎密度之间的相关性，最直接的原因是猎物对密集海草的栖息地偏好。我们报告了另一个支持这一结论的实验，该实验表明栖息地偏好在最早的时机就会表现出来。然而，这种栖息地偏好可能是由捕食压力所选择的。
