ABSTRACT: Competition for limited space is an important driver of benthic community structure on coral reefs. Studies of coral-algae and coral-sponge interactions often show competitive dominance of algae and sponges over corals, but little is known about the outcomes when these groups compete in a multispecies context. Multispecies competition is increasingly common on Caribbean coral reefs as environmental degradation drives loss of reef-building corals and proliferation of alternative organisms such as algae and sponges. New methods are needed to understand multispecies competition, whose outcomes can differ widely from pairwise competition and range from coexistence to exclusion. In this study, we used 3D photogrammetry and image analyses to compare pairwise and multispecies competition on reefs in the US Virgin Islands. Sponges (Desmapsamma anchorata, Aplysina cauliformis) and macroalgae (Lobophora variegata) were attached to coral (Porites astreoides) and arranged to simulate multispecies (coral-sponge-algae) and pairwise (coral-sponge, coral-algae) competition. Photogrammetric 3D models were produced to measure surface area change of coral and sponges, and photographs were analyzed to measure sponge-coral, algae-coral, and algae-sponge overgrowth. Coral lost more surface area and was overgrown more rapidly by the sponge D. anchorata in multispecies treatments, when the sponge was also in contact with algae. Algae contact may confer a competitive advantage to the sponge D. anchorata, but not to A. cauliformis, underscoring the species-specificity of these interactions. This first application of photogrammetry to study competition showed meaningful losses of living coral that, combined with significant overgrowths by competitors detected from image analyses, exposed a novel outcome of multispecies competition.

中文翻译：

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三个方面的三个竞争者：摄影测量法揭示了在用海绵和藻类进行的多物种竞争中珊瑚的迅速繁殖

摘要：有限空间的竞争是珊瑚礁底栖生物群落结构的重要驱动力。对珊瑚-藻类和珊瑚-海绵相互作用的研究通常显示藻类和海绵比珊瑚具有竞争优势，但是当这些群体在多物种环境中竞争时，对结果的了解却很少。由于环境退化导致造礁珊瑚的丧失和藻类和海绵等替代生物的扩散，加勒比珊瑚礁上的多物种竞争越来越普遍。需要新的方法来理解多物种竞争，其结果可能与成对竞争差异很大，范围从共存到排斥。在这项研究中，我们使用3D摄影测量法和图像分析来比较美属维尔京群岛的成对成对和多物种竞争。海绵（将Desmapsamma anchorata，Aplysina cauliformis和Macro藻类（Lobophora variegata）附着在珊瑚（Porites astreoides）上，并模拟多物种（coral-sponge-algae）和成对（coral-sponge，coral-algae）的竞争。制作了摄影测量的3D模型以测量珊瑚和海绵的表面积变化，并对照片进行分析以测量海绵珊瑚，藻类珊瑚和藻类海绵的过度生长。当海绵还与藻类接触时，在多物种处理中，珊瑚损失了更多的表面积，并且被海绵D. anchorata更快地长满。藻类的接触可能会给海绵D. anchorata带来竞争优势，但不会给A. cauliformis带来竞争优势。，强调了这些相互作用的物种特异性。摄影测量法在研究竞争中的首次应用表明，活珊瑚的大量损失，再加上从图像分析中检测到的竞争对手的大量繁殖，暴露了多物种竞争的新成果。