Bottom-up and top-down controls on coral reef sponges: disentangling within-habitat and between-habitat processes.
Bottom-up and top-down controls on coral reef sponges: disentangling within-habitat and between-habitat processes.
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对珊瑚礁海绵的自下而上和自上而下的控制：解开栖息地内和栖息地之间的过程。
作者：
J. Wulff
关于自上而下与自下而上控制的两极分化争论已经让位于对许多系统中资源和消费者控制的更细致的理解，但珊瑚礁海绵最近被认为与其他群体不同，因为它们完全受到自上而下的控制。这种说法遭到了完全自下而上控制的报告的反驳，这两个结论都是基于对同一物种的研究。珊瑚礁的加速恶化促使我们了解消费者或营养物质或两者控制着海绵等关键生态系统角色的背景。因此，将 12 种常见加勒比珊瑚礁海绵物种的基因型和大小受控的个体在野外移植到捕食者、竞争者和海绵所消耗的超微型浮游生物不同的五种环境中。实验移植物在 1-9 年期间的生长和存活揭示了海绵的环境依赖性控制。生长的主要控制是自下而上的，更多的超微型浮游生物导致所有 12 个生态和系统发育多样化的物种持续且持续较高的生长率。在珊瑚礁的栖息地内没有发现自上而下的控制。然而，栖息地之间的控制是通过捕食和竞争实现的，食海绵海星将珊瑚礁海绵排除在邻近的海草草甸之外，而生长较快的红树林海绵则将珊瑚礁海绵排除在红树林支柱根之外。这些结果凸显了实验设计细节的重要性，这些细节考虑了行为特质、足够长的时间尺度以及对物种进行适当的分类。对同一物种的研究得出的截然相反的结果也说明了检测自下而上的过程本质上更大的困难以及区分栖息地内与栖息地间模式和过程的重要性。
Polarized debates about top-down vs. bottom-up control have given way to more nuanced understanding of control by both resources and consumers in many systems, but coral reef sponges have recently been asserted to differ from other groups in being controlled exclusively top-down. This assertion has been countered by reports of exclusively bottom-up control, with both conclusions based on studies of the same species. Accelerating deterioration of coral reefs motivates knowing the contexts in which either consumers or nutrients or both control key ecosystem role players like sponges. Accordingly, genotype- and size-controlled individuals of 12 common Caribbean reef sponge species were transplanted, in the field, into five circumstances differing in predators, competitors, and the picoplankton consumed by sponges. Growth and survival of the experimental transplants for periods of 1-9 yr revealed context-dependent control of sponges. Primary control of growth was bottom-up, with more picoplankton resulting in consistent and sustained higher growth rates for all 12 of these ecologically and phylogenetically diverse species. Top-down control was not detected within-habitat, on the coral reef. However, between-habitat control was by predation and competition, with reef sponges excluded from adjacent seagrass meadows by spongivorous starfish, and excluded from mangrove prop roots by faster-growing mangrove sponges. These results highlight the strong importance of experimental design details that consider behavior idiosyncrasies, sufficiently long time scales, and appropriate division of species into categories. Diametrically opposite results from studies of the same species also illustrate the inherently greater difficulty of detecting bottom-up processes and the importance of distinguishing within-habitat vs. between-habitat patterns and processes.