Centre for Biodiversity and Biosecurity, School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
School of Environmental and Rural Science, University of New England (UNE), Armidale, New South Wales, Australia.
Ecology. 2019 Sep;100(9):e02749. doi: 10.1002/ecy.2749. Epub 2019 Jul 24.
Worldwide, anthropogenic change is causing biodiversity loss, disrupting many critical ecosystem functions. Most studies investigating the relationship between biodiversity and ecosystem functioning focus on species richness, predominantly within the context of productivity-related functions. Consequently, there is limited understanding of how other biodiversity measures, such as species evenness (the distribution of abundance among species), affect complex multitrophic functions such as pollination. We explore the effect of species evenness on the ecosystem function of pollination using a controlled experiment with selected plants and insects in flight cages. We manipulated the relative abundances of plant and pollinator species, while holding species richness, composition, dominance order, and total abundance constant. Then, we tested how numerical species evenness affected network structure and consequently, seed production, in our artificial communities. Contrary to our expectation, numerical dominance in plant communities increased complementarity in pollinator use (reduced pollinator sharing) among plant species. As predicted by theory, this increased complementarity resulted in higher seed production for the most dominant and rare plant species in our cages. Our results show that in a controlled experimental setting, numerical species evenness can alter important aspects of plant-pollinator networks and plant reproduction, irrespective of species richness, composition, and total abundance. Extending this understanding of how species evenness affects ecosystem functioning to natural systems is crucial as anthropogenic disturbances continue to alter species' abundances, likely disrupting ecosystem functions long before extinctions occur.
在全球范围内，人为因素导致的变化正在造成生物多样性的丧失，扰乱了许多关键的生态系统功能。大多数研究生物多样性与生态系统功能之间关系的研究都集中在物种丰富度上，主要是在与生产力相关的功能方面。因此，对于其他生物多样性指标（如物种均匀度（物种丰度在物种间的分布））如何影响授粉等复杂的多营养功能，人们的了解有限。我们使用飞行笼中的选定植物和昆虫进行了一项对照实验，探讨了物种均匀度对授粉这一生态系统功能的影响。我们操纵了植物和传粉者物种的相对丰度，同时保持物种丰富度、组成、优势度顺序和总丰度不变。然后，我们测试了数量物种均匀度如何影响网络结构，进而影响我们人工群落中的种子产量。与我们的预期相反，植物群落中的数量优势增加了植物物种之间传粉者利用的互补性（减少了传粉者的共享）。正如理论所预测的那样，这种互补性的增加导致我们笼中最占优势和最稀有的植物物种的种子产量更高。我们的结果表明，在受控实验环境中，数量物种均匀度可以改变植物-传粉者网络和植物繁殖的重要方面，而与物种丰富度、组成和总丰度无关。将物种均匀度如何影响生态系统功能的这种理解扩展到自然系统至关重要，因为人为干扰继续改变物种的丰度，可能在灭绝发生之前很久就扰乱了生态系统功能。
