Department of Biological Sciences, California State University, Sacramento, Sacramento, California, United States of America.
PLoS One. 2012;7(7):e41809. doi: 10.1371/journal.pone.0041809. Epub 2012 Jul 23.
Trade-offs among species' ecological interactions is a pervasive explanation for species coexistence. The traits associated with trade-offs are typically measured to mechanistically explain species coexistence at a single spatial scale. However, species potentially interact at multiple scales and this may be reflected in the traits among coexisting species. I quantified species' ecological traits associated with the trade-offs expected at both local (competitive ability and predator tolerance) and regional (competitive ability and colonization rate) community scales. The most common species (four protozoa and a rotifer) from the middle trophic level of a pitcher plant (Sarracenia purpurea) inquiline community were used to link species traits to previously observed patterns of species diversity and abundance. Traits associated with trade-offs (competitive ability, predator tolerance, and colonization rate) and other ecological traits (size, growth rate, and carrying capacity) were measured for each of the focal species. Traits were correlated with one another with a negative relationship indicative of a trade-off. Protozoan and rotifer species exhibited a negative relationship between competitive ability and predator tolerance, indicative of coexistence at the local community scale. There was no relationship between competitive ability and colonization rate. Size, growth rate, and carrying capacity were correlated with each other and the trade-off traits: Size was related to both competitive ability and predator tolerance, but growth rate and carrying capacity were correlated with predator tolerance. When partial correlations were conducted controlling for size, growth rate and carrying capacity, the trade-offs largely disappeared. These results imply that body size is the trait that provides the basis for ecological interactions and trade-offs. Altogether, this study showed that the examination of species' traits in the context of coexistence at different scales can contribute to our understanding of the mechanisms underlying community structure.
物种间生态相互作用的权衡是物种共存的普遍解释。与权衡相关的特征通常被测量，以在单一空间尺度上机械地解释物种共存。然而，物种可能在多个尺度上相互作用，这可能反映在共存物种的特征中。我量化了与局部（竞争能力和捕食者容忍度）和区域（竞争能力和殖民率）群落尺度的预期权衡相关的物种生态特征。从中等营养级的猪笼草（Sarracenia purpurea）寄生生物群落中选择最常见的物种（四种原生动物和一种轮虫），将物种特征与之前观察到的物种多样性和丰度模式联系起来。为每个焦点物种测量了与权衡相关的特征（竞争能力、捕食者容忍度和殖民率）和其他生态特征（大小、增长率和承载能力）。特征彼此相关，具有负相关关系，表明存在权衡。原生动物和轮虫物种在竞争能力和捕食者容忍度之间表现出负相关关系，表明在当地群落尺度上共存。竞争能力和殖民率之间没有关系。大小、增长率和承载能力相互关联，与权衡特征相关：大小与竞争能力和捕食者容忍度都有关，但增长率和承载能力与捕食者容忍度有关。当进行控制大小、增长率和承载能力的偏相关时，权衡关系在很大程度上消失了。这些结果表明，体型是提供生态相互作用和权衡基础的特征。总之，这项研究表明，在不同尺度上共存的物种特征的研究可以帮助我们理解群落结构的机制。
