Philpott Stacy M, Soong Oliver, Lowenstein Jacob H, Pulido Astrid Luz, Lopez Diego Tobar, Flynn Dan F B, DeClerck Fabrice
Department of Environmental Sciences, University of Toledo, Toledo, Ohio 43606, USA.
Ecol Appl. 2009 Oct;19(7):1858-67. doi: 10.1890/08-1928.1.
In agroecosystems, biodiversity correlates with ecosystem function, yet mechanisms driving these relationships are often unknown. Examining traits and functional classifications of organisms providing ecosystem functions may provide insight into the mechanisms. Birds are important predators of insects, including pests. However, biological simplification of agroforests may decrease provisioning of this pest removal service by reducing bird taxonomic and functional diversity. A recent meta-analysis of bird exclosure studies from a range of agroecosystems in Central America concluded that higher bird richness is associated with significantly greater arthropod removal, yet the mechanism remains unclear. We conducted a meta-analysis of the same data to examine whether birds demonstrate functional complementarity in tropical agroforests. We classified birds according to relevant traits (body mass, foraging strategy, foraging Strata, and diet) and then examined how design of functional classification, including trait selection, classification methods, and the functional diversity metric used affect the suitability of different classifications as predictors of ecosystem services. We determined that vegetation characteristics are not likely drivers of arthropod removal by birds. For some functional classifications, functional richness positively correlated with arthropod removal, indicating that species complementarity may be an important mechanism behind this ecosystem function. The predictive ability of functional classifications increased with the number of traits included in the classification. For the two best classifications examined, functional group richness was a better predictor of arthropod reduction than other metrics of functional diversity (FD and Rao's Q). However, no functional classification predicted arthropod removal better than simple species richness; thus other factors may be important. Our analysis indicates that the sampling effect may also play a role, as one species and two functional groups were responsible for disproportionate effects of arthropod removal.
在农业生态系统中，生物多样性与生态系统功能相关，但驱动这些关系的机制往往不明。研究提供生态系统功能的生物的性状和功能分类，可能有助于深入了解其机制。鸟类是包括害虫在内的昆虫的重要捕食者。然而，农林生态系统的生物简化可能会通过降低鸟类的分类和功能多样性，减少这种害虫控制服务的提供。最近对中美洲一系列农业生态系统中鸟类排除实验的荟萃分析得出结论，较高的鸟类丰富度与显著更多的节肢动物被捕食相关，但机制仍不清楚。我们对相同数据进行了荟萃分析，以研究鸟类在热带农林生态系统中是否表现出功能互补性。我们根据相关性状（体重、觅食策略、觅食层次和食性）对鸟类进行分类，然后研究功能分类的设计，包括性状选择、分类方法以及所使用的功能多样性指标，如何影响不同分类作为生态系统服务预测指标的适用性。我们确定植被特征不太可能是鸟类捕食节肢动物的驱动因素。对于某些功能分类，功能丰富度与节肢动物被捕食呈正相关，这表明物种互补性可能是这种生态系统功能背后的重要机制。功能分类的预测能力随着分类中包含的性状数量增加而提高。对于所研究的两个最佳分类，功能组丰富度比其他功能多样性指标（功能多样性指数和Rao氏Q指数）更能预测节肢动物数量的减少。然而，没有一种功能分类比简单的物种丰富度更能预测节肢动物被捕食的情况；因此其他因素可能也很重要。我们的分析表明，抽样效应可能也起了作用，因为一个物种和两个功能组对节肢动物被捕食产生了不成比例的影响。
