Wahl Martin, Hay Mark E
Institute of Marine Sciences, University of North Carolina at Chapel Hill, 28557, Morehead City, NC, USA.
Oecologia. 1995 Jun;102(3):329-340. doi: 10.1007/BF00329800.
The potential for spatial associations between palatable and unpalatable plant species to reduce herbivore pressure on the palatable species has been described as associational resistance, associational refuge or associational defense for numerous terrestrial and marine communities. One of the closest associations between species-epibiosis-has not been thoroughly investigated in this regard. In this study we evaluated how different associations between host seaweeds and epibiotic plants and animals influenced the movement of an omnivorous sea urchin (Arbacia punctulata) to the host and subsequent feeding on the host. A. punctulata showed clear preferences when given pairwise choices between 12 prey species (3 animals, 9 algae). These preferences were consistent and allowed us to rank the six epibiont species and six host species linearly from least to most preferred by A. punculata. Most host-epibiont associations dramatically changed urchin preference, increasing or decreasing urchin grazing on fouled hosts as compared to clean conspecifics. Herbivory on the host increased when the epibiont was more preferred, and decreased when it was less preferred than the unfouled host alga. Taking the host species as a point of reference, we classified epibiosis-caused decrease in herbivory as associational resistance, while epibiont-caused increases in herbivory were defined as shared doom. These epibiont-host-herbivore interactions could select for hosts that facilitate the growth of certain low preference epibionts on their surfaces in situations where the resulting decreases in herbivory would offset the various negative effects of being fouled. In contrast, in situations where herbivores are common, the negative effects of being fouled by palatable epibionts may be much greater than is generally assumed. In our assays, unpalatable hosts fouled by palatable epibionts became much more attractive to urchins and rose several ranks on the urchins' preference hierarchy.
在许多陆地和海洋群落中，可口植物物种与不可口植物物种之间的空间关联有可能减轻食草动物对可口物种的压力，这被描述为关联抗性、关联避难所或关联防御。物种之间最紧密的关联之一——体表共生——在这方面尚未得到充分研究。在本研究中，我们评估了宿主海藻与体表共生植物和动物之间的不同关联如何影响杂食性海胆（刺冠海胆）向宿主的移动以及随后对宿主的取食。当在12种猎物物种（3种动物、9种藻类）之间进行两两选择时，刺冠海胆表现出明显的偏好。这些偏好是一致的，使我们能够将6种体表共生物种和6种宿主物种按照刺冠海胆的偏好程度从最低到最高进行线性排序。大多数宿主 - 体表共生关联极大地改变了海胆的偏好，与干净的同种宿主相比，有附着物的宿主上的海胆啃食量增加或减少。当体表共生生物更受青睐时，宿主上的食草作用增加；当它比未被污染的宿主藻类更不受青睐时，食草作用减少。以宿主物种为参考点，我们将体表共生导致的食草作用减少归类为关联抗性，而体表共生导致的食草作用增加则被定义为共同厄运。这些体表共生生物 - 宿主 - 食草动物的相互作用可能会选择那些在体表促进某些低偏好体表共生生物生长的宿主，在这种情况下，由此导致的食草作用减少将抵消被污染的各种负面影响。相比之下，在食草动物常见的情况下，被可口体表共生生物污染的负面影响可能比通常认为的要大得多。在我们的试验中，被可口体表共生生物污染的不可口宿主对海胆变得更具吸引力，并在海胆的偏好等级中上升了几个等级。
