Levin Phillip S
Department of Zoology and Center for Marine Biology, University of New Hampshire, 03824, Durham, NH, USA.
Oecologia. 1993 May;94(2):176-185. doi: 10.1007/BF00341315.
Pronounced spatial variation in recruitment occurs in many marine invertebrate and fish populations and is thought to be critical to the demography of these species. In this study I examined the importance of habitat structure and the presence of conspecific residents to spatial variation in larval settlement and recruitment in a temperate fish Tautogolabrus adspersus. I define settlement as the movement of individuals from the water column to the benthic habitat, while I refer to recruitment as numbers of individuals surviving some arbitrary period of time after settlement. Experiments in which standard habitats were stocked with conspecifics showed that resident conspecifics were not an important factor contributing to small-scale variability in recruitment. Further correlative analyses demonstrated that large-scale variation in recruitment could not be explained by variability in older age classes. By contrast, manipulations of macroalgal structure within a kelp bed demonstrated that recruitment was significantly higher in habitats with a dense understory of foliose and filamentous algae than in habitats with only crustose algae. Understory algae varied in their pattern of disperison among sites, and the dispersion of fish matched that of the plants. In order to determine the effects of differences in patterns of algal dispersion on the demography of associated T. adspersus populations, I used experimental habitat units to manipulate patterns of dispersion. Settlement was significantly greater to randomly placed versus clumped habitats; however, no differences in recruitment between random and clumped habitats were detected. Because recruitment is a function of the numbers of settlers minus the subsequent loss of settlers, rates of mortality or migration must have been higher in the randomly placed habitats. These results are counter to the current paradigm for reef fishes which suggests that larval settlement is the crucial demographic process producing variability in population abundance. In this experiment patterns of settlement were modified by varying the patch structure of the habitat.
许多海洋无脊椎动物和鱼类种群的补充存在显著的空间变异，这被认为对这些物种的种群统计学至关重要。在本研究中，我研究了栖息地结构和同种居民的存在对温带鱼类细纹狮子鱼（Tautogolabrus adspersus）幼体沉降和补充的空间变异的重要性。我将沉降定义为个体从水柱移动到底栖栖息地，而将补充定义为沉降后在任意一段时间内存活的个体数量。在标准栖息地投放同种个体的实验表明，同种居民并非导致补充小规模变异的重要因素。进一步的相关分析表明，补充的大规模变异无法用老年个体的变异性来解释。相比之下，对海带床内大型藻类结构的操纵表明，在具有密集叶状和丝状藻类下层的栖息地中，补充量显著高于仅具有壳状藻类的栖息地。下层藻类在不同地点的分布模式不同，鱼类的分布与植物的分布相匹配。为了确定藻类分布模式差异对相关细纹狮子鱼种群统计学的影响，我使用实验性栖息地单元来操纵分布模式。随机放置的栖息地的沉降量明显大于聚集的栖息地；然而，未检测到随机栖息地和聚集栖息地在补充方面的差异。由于补充是定居者数量减去随后定居者损失的函数，随机放置的栖息地中的死亡率或迁移率必定更高。这些结果与当前关于珊瑚礁鱼类的范式相反，该范式表明幼体沉降是导致种群丰度变异的关键种群统计学过程。在本实验中，通过改变栖息地的斑块结构来改变沉降模式。
