Coexistence of annual plants: generalist seed predation weakens the storage effect.
Coexistence of annual plants: generalist seed predation weakens the storage effect.
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一年生植物共存：泛型种子捕食削弱了储存效果。
DOI：
10.1890/08-0207.1
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发表时间：
2009
期刊：
影响因子：
4.8
通讯作者：
P. Chesson
中科院分区：
文献类型：
--
作者：
J. J. Kuang;P. Chesson
我们调查的影响种子捕食竞争的一年生植物共存。我们证明了捕食的作用，这是相反的传统智慧，捕食通过降低竞争的强度，促进共存。在竞争性共存涉及种内竞争超过种间竞争的常见情况下，捕食可以通过减少竞争的总体规模来破坏共存，以不会导致种内和种间差异效应的“明显竞争”取代竞争。我们证明了这一结果的情况下，共存发生的“存储效应”在一个可变的环境。当环境与竞争相互作用，为物种从低密度增加创造机会时，就会产生储存效应。当一个物种处于高密度时，储存效应的关键是种群增长对环境的响应与其对竞争的响应之间的正协方差。这一结果阻止了高密度物种利用有利的环境条件。低密度的物种具有较低的协方差，可以利用有利的环境条件，使其比高密度物种更具优势，促进其从低密度恢复。因此，促进了物种的共存。在这里，我们发现，密度依赖性捕食降低人口密度，从而削弱竞争，取代竞争与明显的竞争，这不与环境的协变。因此，环境和竞争之间的协方差被削弱，降低了低密度物种的优势。这些物种仍然通过竞争和明显竞争的结合进行强烈的相互作用，但低密度优势的减少降低了它们共存的能力。虽然这一结果是专门证明的存储效果，重点是一年生植物群落，所涉及的原则是一般的。
We investigate the effect of seed predation on the coexistence of competing annual plants. We demonstrate a role for predation that is opposite to the conventional wisdom that predation promotes coexistence by reducing the intensity of competition. In the common situation where competitive coexistence involves intraspecific competition exceeding interspecific competition, predation can undermine coexistence by reducing the overall magnitude of competition, replacing competition with "apparent competition" in a way that does not lead to differential intraspecific and interspecific effects. We demonstrate this outcome in the case where coexistence occurs by "the storage effect" in a variable environment. The storage effect arises when the environment interacts with competition to create opportunities for species to increase from low density. Critical to the storage effect is positive covariance between the response of population growth to the environment and its response to competition, when a species is at high density. This outcome prevents species at high density from taking advantage of favorable environmental conditions. A species at low density has lower covariance and can take advantage of favorable environmental conditions, giving it an advantage over a high-density species, fostering its recovery from low density. Hence, species coexistence is promoted. Here we find that density-dependent predation lowers population densities, and so weakens competition, replacing competition with apparent competition, which does not covary with the environment. As a consequence, covariance between environment and competition is weakened, reducing the advantage to a species at low density. The species still strongly interact through the combination of competition and apparent competition, but the reduced low-density advantage reduces their ability to coexist. Although this result is demonstrated specifically for the storage effect with a focus on annual plant communities, the principles involved are general ones.