Benedetti-Cecchi L, Bulleri F, Cinelli F
Dipartimento di Scienze dell'Uomo e dell'Ambiente, via A. Volta 6, 56126 Pisa, Italy e-mail:
Oecologia. 2000 May;123(3):406-417. doi: 10.1007/s004420051028.
This study examined the interactive effects of grazing by limpets and inclination of the substratum in maintaining differences between mid-shore and low-shore assemblages of algae in the northwest Mediterranean, at different scales of space and through time. Alternative models leading to different predictions about these effects were proposed and tested. Limpets were excluded by fences from areas of the substratum at mid levels on the shore. The response of algal assemblages to this manipulation was compared with control and enclosure plots at the same level, and with unmanipulated plots in the low shore where limpets are less abundant. The effects of limpets were examined at several replicated sites (0.1-4 km apart) for each slope of the substratum (nearly horizontal vs vertical), at different locations (hundreds of kilometres apart) and at different times. Individual taxa responded differently to limpet exclusion. The percentage cover of the coarsely branched and filamentous algae increased significantly in exclosure plots, in some loser reaching values found on the low shore. These patterns, however, varied greatly from shore to shore and significant effects were found both on horizontal and vertical substrata. Multivariate analyses indicated that grazing by limpets accounted for about 20% of the differences between mid-shore and low-shore assemblages. This effect was independent of substratum inclination and was consistent in space and time, suggesting that physical conditions were not as stressful for macroalgae on vertical substrata as initially supposed. Variable recruitment of algae is proposed as a possible explanation for the lack of consistency in the effects of limpets at the scale of the shore. The results of this study emphasize the need for multiple-scale analyses of the interactive effects of physical and biological factors to understand the organization of natural assemblages.
本研究探讨了帽贝啃食与基质倾斜度之间的交互作用，这种交互作用在不同空间尺度和时间范围内，维持了地中海西北部中潮间带和低潮间带藻类群落之间的差异。我们提出并测试了关于这些效应的不同预测的替代模型。通过围栏将帽贝排除在海岸中部基质区域之外。将藻类群落对这种操作的反应与同一水平的对照区和围合区进行比较，并与低潮间带未受操作的区域（帽贝数量较少）进行比较。在基质的每个坡度（近乎水平与垂直）的几个重复地点（相距0.1 - 4公里）、不同位置（相距数百公里）以及不同时间，研究了帽贝的影响。各个分类单元对帽贝排除的反应不同。在排除区，粗分支和丝状藻类的覆盖百分比显著增加，在某些情况下达到了低潮间带的水平。然而，这些模式在不同海岸之间差异很大，在水平和垂直基质上都发现了显著影响。多变量分析表明，帽贝啃食占中潮间带和低潮间带群落差异的约20%。这种效应与基质倾斜度无关，在空间和时间上是一致的，这表明垂直基质上的物理条件对大型藻类的压力并不像最初设想的那么大。藻类的可变补充被认为是帽贝在海岸尺度上效应缺乏一致性的一个可能解释。本研究结果强调了对物理和生物因素的交互作用进行多尺度分析以理解自然群落组织的必要性。
