Bulleri Fabio, Benedetti-Cecchi Lisandro
Dipartimento di Biologia, Università di Pisa, Via A. Volta 6, Pisa, 56126, Italy,
Oecologia. 2006 Sep;149(3):482-92. doi: 10.1007/s00442-006-0459-3. Epub 2006 Aug 1.
Understanding the mechanisms producing and maintaining discontinuities between patches in mosaics of habitats is necessary to predict changes in patterns of abundance and distribution of species. On temperate rocky reefs, physical and biological disturbance can result in a mosaic of patches of encrusting coralline, turf- or canopy-forming algae. We experimentally investigated the effects of disturbance within and at the boundary between these patches, in order to identify mechanisms accounting for re-colonisation of space and to assess whether the response of boundaries can alter the relative size of contrasting habitats. Also, we tested whether the resilience of the different types of assemblages depends on species richness (i.e. number of taxa present) of habitats or, alternatively, on other properties of systems like differences in life-history traits of dominating species. Although the nature of the mechanisms generating differences among habitats changed among different stages of the colonisation, local processes (within patches) prevailed over larger scale processes (among patches) in determining early patterns of colonisation of space in mosaics. By the end of the experiment, assemblages in clearings at boundaries had recovered to the undisturbed reference condition, in contrast to clearings within barren patches or algal turfs. Boundaries represent, therefore, relatively more stable components of the mosaic, with greater resilience than adjacent habitats. Although sea urchins are often indicated as the main force regulating the proportion of contrasting habitats on shallow rocky reefs, determining the nature of variation in the interaction between species dominating each type of habitat is crucial to understand dynamics of mosaics. Finally, our study provides evidence that resilience could not be entirely controlled by initial species diversity, suggesting that different proportions of dominant taxa could influence the stability of natural systems.
了解生境镶嵌体中斑块之间产生和维持不连续性的机制，对于预测物种丰度和分布模式的变化是必要的。在温带岩石礁上，物理和生物干扰可导致形成由结壳珊瑚藻、草皮或冠层形成藻类组成的斑块镶嵌体。我们通过实验研究了这些斑块内部和边界处干扰的影响，以确定空间重新定殖的机制，并评估边界的响应是否会改变不同生境的相对大小。此外，我们还测试了不同类型组合的恢复力是否取决于生境的物种丰富度（即存在的分类单元数量），或者相反，是否取决于系统的其他特性，如优势物种生活史特征的差异。尽管在定殖的不同阶段，生境之间产生差异的机制性质有所变化，但在决定镶嵌体中空间定殖的早期模式时，局部过程（斑块内部）比大规模过程（斑块之间）更为重要。到实验结束时，与贫瘠斑块或藻类草皮内的空地相比，边界处空地的组合已恢复到未受干扰的参考状态。因此，边界代表了镶嵌体中相对更稳定的组成部分，比相邻生境具有更大的恢复力。尽管海胆通常被认为是调节浅海岩石礁上不同生境比例的主要力量，但确定主导每种生境的物种之间相互作用变化的性质，对于理解镶嵌体的动态至关重要。最后，我们的研究提供了证据，表明恢复力不能完全由初始物种多样性控制，这表明优势分类单元的不同比例可能会影响自然系统的稳定性。
