Okamura B
Department of Zoology, University of California, 94720, Berkeley, CA, USA.
Oecologia. 1986 Jun;69(3):341-347. doi: 10.1007/BF00377054.
The mussel Mytilus edulis typically occurs in aggregations and several consequences of living in groups were studied. Isolated individuals and individuals associated in relatively small groups (6-9 mussles/group) grew more and therefore had greater reproductive output than mussels associated with relatively large groups of 21-28 individuals. Mussels located in the centers of groups exhibited reduced growth and thus lower reproduction relative to mussels located on the edges of groups whose growth and reproduction was similar to that of isolated individuals. Sampling from natural populations indicated that most mussels grow within the matrix of very large groups and hence will experience reduced growth and reproduction. Patterns of growth exhibited by mussels in association with living and model mussels showed that the adverse effects on growth exhibited by mussels in relatively large groups are not a function of the mere physical relief of a mussel clump, but are caused by some property of living neighbors.Laboratory experiments on mussel predation by the crab Pachygrapsus crassipes indicated that crabs prey disproportionately on mussels growing on the edges of groups.The consequences of group living in mobile and nonmobile organisms are considered, and it is suggested that a greater number of negative effects will arise in groups as mobility decreases. In addition, the noted ecological similarity between groups of sessile organisms and spreading clones and its evolutionary implications are discussed.
紫贻贝通常聚集生活，人们研究了群居生活带来的几个后果。与21 - 28个个体组成的相对大群体中的贻贝相比，孤立的个体以及组成相对小群体（每组6 - 9个贻贝）的个体生长得更快，因此繁殖产出也更高。相对于位于群体边缘、生长和繁殖情况与孤立个体相似的贻贝，位于群体中心的贻贝生长减缓，繁殖能力也较低。对自然种群的抽样表明，大多数贻贝生长在非常大的群体之中，因此会经历生长和繁殖的减缓。与活贻贝和模型贻贝共生的贻贝所呈现的生长模式表明，相对大群体中的贻贝对生长产生的不利影响并非仅仅是贻贝聚集的物理效应，而是由活邻居的某些特性导致的。关于厚蟹对贻贝捕食的实验室实验表明，螃蟹对生长在群体边缘的贻贝的捕食比例过高。文中考虑了群居对活动和不活动生物的影响，并指出随着活动能力下降，群体中会产生更多负面影响。此外，还讨论了固着生物群体与扩散克隆之间显著的生态相似性及其进化意义。
