Trade-off between competitive ability and antipredator adaptation in a freshwater amphipod species complex
Trade-off between competitive ability and antipredator adaptation in a freshwater amphipod species complex
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淡水片足类物种复合体竞争能力和反捕食适应之间的权衡
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发表时间：
2002
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通讯作者：
Gary A. Wellborn
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作者：
Gary A. Wellborn
身体大小影响许多生理和生态过程，因此身体大小的适应性变化可能对个体产生不同的影响。片足类在Hyalella阿兹台克物种复杂，身体大小的分歧似乎是由适应不同的制度，在不同的栖息地类型经历的大小偏置死亡率驱动。在这里，我想问的是，体型和与体型相关的性状是如何影响体型大的物种和体型小的物种的竞争能力的。我研究了竞争能力，在这两个物种使用析因实验中，每个物种的性能进行了评估，在所有的组合的存在和不存在的异特异性端足类物种与存在和不存在的蜗牛物种交叉。结果表明，大小种透明藻的竞争能力存在显著差异，大种透明藻是上级竞争者。大型物种对小型物种的竞争效应是巨大的，并导致小型物种的丰度、体型和繁殖力显著降低。相比之下，大型物种的性能不受小型物种存在的显著影响。这种竞争的不对称性也出现在与蜗牛的竞争性相互作用中。小的物种似乎“权衡”的竞争能力，以生存在栖息地与掠食性鱼类，而大的物种，这是能够获得一个大小避难所捕食，具有的特点，赋予强大的竞争能力。然而，由于栖息地在权衡的成本效益结构的差异，竞争介导的自然选择可能是更激烈的大型物种比小型物种，一个条件，可能会提高进化的分歧，在身体大小。
Body size influences many physiological and ecological processes, and thus adaptive change in body size may hold diverse consequences for individuals. For amphipods in the Hyalella azteca species complex, divergence in body size appears to be driven by adaptation to disparate regimes of size-biased mortality experienced in different habitat types. Here I ask how size and size-related traits influence competitive ability of large- bodied and small-bodied species. I examined competitive ability in both species using a factorial experiment in which the performance of each species was assessed in all com- binations of the presence and absence of the heterospecific amphipod species crossed with the presence and absence of a snail species. Results demonstrated that the large and small Hyalella species differ substantially in competitive ability, with the large species being the superior general competitor. The competitive effect of the large species on the small species was substantial and caused significant reductions in abundance, body size, and fecundity of the small species. In contrast, performance of the large species was not affected sig- nificantly by presence of the small species. This competitive asymmetry was also seen in competitive interactions with snails. The small species appears to "trade off" competitive ability in order to survive in habitats with predatory fish, whereas the large species, which is able to obtain a size refuge from predation, has traits that confer strong competitive ability. Because of habitat differences in the cost-benefit structure of the trade-off, however, competition-mediated natural selection may be more intense in the large species than in the small species, a condition that may enhance evolutionary divergence in body size.