Testing whether productivity mediates the occurrence of alternate stable states and assembly cycles in a model microcosm system
Testing whether productivity mediates the occurrence of alternate stable states and assembly cycles in a model microcosm system
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测试生产力是否介导模型微观系统中交替稳定状态和装配周期的发生
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发表时间：
2008
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通讯作者：
J. Fox
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作者：
J. Fox
反映群落集合历史的初始条件在什么时候会影响最终的群落状态？比较实地研究和最近的理论表明，在高生产率的初始条件的问题，因为不可侵入的交替稳定状态和组装周期更有可能在高生产率。然而，这一预测及其背后的机制尚未得到实验验证。另一种假设是，初始条件相对不重要，群落通常由具有适当特征的物种组成，这些特征可能随生产力而变化。我组装的原生生物和轮虫社区在实验室的微观世界从一个物种丰富，营养多样的物种池使用所有可能的组合的两个初始条件和四个生产力水平。在群落接近其最终状态后，最初未能持续存在的物种的入侵测试了这些最终状态的可入侵性，并测试了组装周期。我还研究了当地（微观世界内）多样性和区域多样性（给定生产力水平的所有微观世界的总物种丰富度）如何随生产力而变化。比较实地工作已经使用这种规模依赖的多样性生产力的关系作为证据的组装历史的影响。生产力有一个温和的影响，最终入侵前的物种组成，而初始条件有一个非常弱的影响。大多数入侵失败，成功入侵和入侵后预防的频率并不随生产力而变化。相反，在入侵前最常出现的物种也是最成功的入侵者，也是最不可能在入侵后灭绝的物种。地方和区域的富裕程度并不因生产力的不同而有很大差异。总的来说，结果表明，最终的社区是可预测的，由具有适当性状的物种组成，而不是初始条件的不可预测的结果。
When do initial conditions, which reflect the assembly history of a community, affect the final community state? Comparative field studies and recent theory suggest that initial conditions matter at high productivity, because uninvasible alternate stable states and assembly cycles are more likely at high productivity. However, this prediction and the mechanisms behind it have not been tested experimentally. An alternative hypothesis is that initial conditions are relatively unimportant, and that communities generally are comprised of species with appropriate traits, which might vary with productivity. I assembled communities of protists and rotifers in laboratory microcosms from a species-rich, trophically-diverse species pool using all possible combinations of two initial conditions and four productivity levels. After communities approached their final states, invasions by the species that initially failed to persist tested the invasibility of those final states and tested for assembly cycles. I also examined how local (within-microcosm) diversity and regional diversity (total species richness of all microcosms of a given productivity level) varied with productivity. Comparative field work has used such scale-dependent diversity-productivity relationships as evidence for effects of assembly history. Productivity had a modest effect on final pre-invasion species composition, while initial conditions had a very weak effect. Most invasions failed, and the frequency of successful invasions and of post-invasion extinctions did not vary with productivity. Instead, species that were present most frequently pre-invasion were also the most successful invaders, and the least-likely species to go extinct post-invasion. Local and regional richness did not vary substantially with productivity. Overall, the results suggest that final communities are predictably comprised of species with appropriate traits, and are not an unpredictable outcome of initial conditions.