Influence of a dominant consumer species reverses at increased diversity
Influence of a dominant consumer species reverses at increased diversity
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DOI：
10.1890/10-1785.1
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发表时间：
2012-04-01
期刊：
影响因子：
4.8
通讯作者：
Chiriboga, Angel I.
中科院分区：
文献类型：
--
作者：
Brandt, Margarita;Witman, Jon D.;Chiriboga, Angel I.
理论和实验表明，消费者多样性的变化会影响底栖群落结构和生态系统功能。尽管消费者多样性的影响已经在实验室和现场进行了测试，但对潮下带消费者多样性的影响知之甚少，潮下带是最大的海洋栖息地之一。我们研究了加拉帕戈斯群岛一个自然潮下生境中海胆的放牧对藻类丰度和底栖群落结构的影响。三种海胆(Eucidaris、Lytechinus和Tripneustes)在包容式笼子里操作，采用了三个物种丰富度水平(一种、两种和三种)的替换设计，所有可能的两种海胆组合。同一性是影响底物放牧和底栖生物群落结构变化的主要因素。三个两种组合中有两个放牧超过预期，这表明了丰富度效应，但分析表明，放牧增加是由于最大的、有商业价值的海胆物种Tripneustes的抽样效应。在实验结束时，真核生物、石龙子和雷公藤单独处理的底栖生物群落结构有显著差异，表明资源利用发生了分化。Tripneustes围栏内的群落以丰富的甲壳珊瑚藻类和放牧底物为特征，而未围栏的群落则以丰富的绿叶藻类(Ulva sp.)为特征。该系统的一个意想不到的紧急性质是，物种最丰富的海胆组合产量不足，比任何其他有Tripneustes的组合吃的都少，有效地扭转了在两个物种处理中观察到的主导影响。虽然还需要进一步的实验来弄清低产的机制，但这可能与物种间的相互作用随着丰富度从两个物种增加到三个物种而发生变化，或者与依赖密度的Tripneustes放牧有关。这项研究强调了在所考虑的整个物种丰富度范围内评估消费者丰富度影响的一般重要性，因为最丰富的物种消费者群体的表现不能通过操纵中等水平的消费者物种丰富度来预测。
Theory and experiments indicate that changes in consumer diversity affect benthic community structure and ecosystem functioning. Although the effects of consumer diversity have been tested in the laboratory and the field, little is known about effects of consumer diversity in the subtidal zone, one of the largest marine habitats. We investigated the grazing effects of sea urchins on algal abundance and benthic community structure in a natural subtidal habitat of the Galapagos Islands. Three species of urchins (Eucidaris, Lytechinus, and Tripneustes) were manipulated in inclusion cages following a replacement design with three levels of species richness (one, two, and three species) with all possible two-species urchin combinations. Identity was the main factor accounting for changes in the percentage of substrate grazed and benthic community structure. Two out of the three two-species assemblages grazed more than expected, suggesting a richness effect, but analyses revealed that this increased grazing was due to a sampling effect of the largest and commercially valued urchin species, Tripneustes. Benthic community structure in treatments with Eucidaris, Lytechinus, and Tripneustes alone was significantly different at the end of the experiment, suggesting that resource use differentiation occurred. Communities in Tripneustes enclosures were characterized by abundant crustose coralline algae and grazed substrate, while those without it contained abundant green foliose algae (Ulva sp.). An unexpected emergent property of the system was that the most species-rich urchin assemblage underyielded, grazing less than any other assemblage with Tripneustes, effectively reversing its dominant influence observed in the two-species treatments. While further experiments are needed to discern the mechanisms of underyielding, it may be related to changing interspecific interactions as richness increases from two to three species or to density-dependent Tripneustes grazing. This study highlights the general importance of evaluating consumer richness effects across the entire range of species richness considered, as the performance of the most species-rich consumer assemblage could not be predicted by manipulations of intermediate levels of consumer species richness.