Cardinale Bradley J, Srivastava Diane S, Duffy J Emmett, Wright Justin P, Downing Amy L, Sankaran Mahesh, Jouseau Claire
Department of Ecology, Evolution and Marine Biology, University of California at Santa Barbara, Santa Barbara, California 93106, USA.
Nature. 2006 Oct 26;443(7114):989-92. doi: 10.1038/nature05202.
Over the past decade, accelerating rates of species extinction have prompted an increasing number of studies to reduce species diversity experimentally and examine how this alters the efficiency by which communities capture resources and convert those into biomass. So far, the generality of patterns and processes observed in individual studies have been the subjects of considerable debate. Here we present a formal meta-analysis of studies that have experimentally manipulated species diversity to examine how it affects the functioning of numerous trophic groups in multiple types of ecosystem. We show that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal trophic group, leading to less complete depletion of resources used by that group. At the same time, analyses reveal that the standing stock of, and resource depletion by, the most species-rich polyculture tends to be no different from that of the single most productive species used in an experiment. Of the known mechanisms that might explain these trends, results are most consistent with what is called the 'sampling effect', which occurs when diverse communities are more likely to contain and become dominated by the most productive species. Whether this mechanism is widespread in natural communities is currently controversial. Patterns we report are remarkably consistent for four different trophic groups (producers, herbivores, detritivores and predators) and two major ecosystem types (aquatic and terrestrial). Collectively, our analyses suggest that the average species loss does indeed affect the functioning of a wide variety of organisms and ecosystems, but the magnitude of these effects is ultimately determined by the identity of species that are going extinct.
在过去十年中，物种灭绝速度不断加快，促使越来越多的研究通过实验来减少物种多样性，并研究这如何改变群落获取资源并将其转化为生物量的效率。到目前为止，在个别研究中观察到的模式和过程的普遍性一直是大量争论的主题。在此，我们对一系列研究进行了正式的荟萃分析，这些研究通过实验操纵物种多样性，以研究其如何影响多种类型生态系统中众多营养级的功能。我们发现，物种丰富度降低的平均效应是减少目标营养级的丰度或生物量，导致该营养级使用的资源消耗得不那么彻底。同时，分析表明，物种最丰富的混养群落的现存生物量和资源消耗往往与实验中使用的单个生产力最高的物种没有差异。在可能解释这些趋势的已知机制中，结果与所谓的“抽样效应”最为一致，当多样化的群落更有可能包含并被生产力最高的物种主导时，就会出现这种效应。这种机制在自然群落中是否普遍存在目前存在争议。我们报告的模式在四个不同的营养级（生产者、食草动物、分解者和捕食者）和两种主要生态系统类型（水生和陆地）中非常一致。总体而言，我们的分析表明，平均物种丧失确实会影响各种各样的生物和生态系统的功能，但这些影响的程度最终取决于正在灭绝的物种的身份。
