Spatially complex habitats provide refuge for prey and mediate many predator–prey interactions. Increasing anthropogenic pressures are eroding such habitats, reducing their complexity and potentially altering ecosystem stability on a global scale. Yet, we have only a rudimentary understanding of how structurally complex habitats create ecological refuges for most ecosystems. Better informed management decisions require an understanding of the mechanisms underpinning the provision of physical refuge and this may be linked to prey size, predator size and predator identity in priority habitats. We tested each of these factors empirically in a model biogenic reef system. Specifically, we tested whether mortality rates of blue mussels (Mytilus edulis) of different sizes differed among: (i) different forms of reef structural distribution (represented as ‘clumped’, ‘patchy’ and ‘sparse’); (ii) predator species identity (shore crab, Carcinus maenas and starfish, Asterias rubens); and (iii) predator size. The survival rate of small mussels was greatest in the clumped experimental habitat and larger predators generally consumed more prey regardless of the structural organisation of treatment. Small mussels were protected from larger A. rubens but not from larger C. maenas in the clumped habitats. The distribution pattern of structural objects, therefore, may be considered a useful proxy for reef complexity when assessing predator–prey interactions, and optimal organisations should be considered based on both prey and predator sizes. These findings are essential to understand ecological processes underpinning predation rates in structurally complex habitats and to inform future restoration and ecological engineering practices.

中文翻译：

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结构间空间较小的栖息地促进贻贝生存和珊瑚礁生成

空间复杂的栖息地为猎物提供庇护，并调节许多捕食者与猎物的相互作用。日益增加的人为压力正在侵蚀这些栖息地，降低其复杂性，并可能改变全球范围内的生态系统稳定性。然而，我们对结构复杂的栖息地如何为大多数生态系统创建生态避难所只有初步的了解。更明智的管理决策需要了解提供物理庇护所的机制，这可能与优先栖息地的猎物大小、捕食者大小和捕食者身份有关。我们在生物礁系统模型中对这些因素进行了实证测试。具体来说，我们测试了不同大小的蓝贻贝（Mytilus edulis）的死亡率是否存在以下差异：（i）不同形式的珊瑚礁结构分布（表示为“丛生”、“斑驳”和“稀疏”）；(ii) 捕食者物种身份（岸蟹、Carcinus maenas 和海星、Asterias rubens）；(iii) 捕食者的大小。在聚集的实验栖息地中，小型贻贝的存活率最高，而无论处理的结构组织如何，较大的捕食者通常都会消耗更多的猎物。在聚集的栖息地中，小贻贝受到保护，免受较大的 A. rubens 的侵害，但无法免受较大的 C. maenas 的侵害。因此，在评估捕食者与被捕食者之间的相互作用时，结构物体的分布模式可能被认为是珊瑚礁复杂性的有用指标，并且应根据被捕食者和捕食者的大小来考虑最佳组织。这些发现对于了解结构复杂的栖息地中支撑捕食率的生态过程以及为未来的恢复和生态工程实践提供信息至关重要。