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人们早就认识到，生物多样性在生态系统的功能运作中起着重要作用，但生态系统服务对生物多样性的依赖关系一直在争论当中。
在现实生态系统中，自然群落由一些高度丰富的优势物种和许多稀有物种组成。丰富度、丰度和优势度的重要性很可能会受到相对丰度随物种丰富度变化程度的影响，以及受到提供服务的群落的有效性和专业化程度的差异的影响。然而，生物多样性的这三个方面通常是在小规模的实验环境中单独测试的，目前仍然缺乏对比它们在现实生态系统中相对重要性的综合研究。
Matteo Dainese，Emily A. Martin以及Ingolf Steffan-Dewenter构思了这项全球综合研究，使用贝叶斯多级建模方法，解决了生物多样性-生态系统功能框架中的三个基本但尚未解决的问题：(1) 丰富度、丰度和优势度是否可以维持现实世界生态系统中的生态系统服务？（2）景观简化是否会因为当地种群多样性的缺失而间接影响生态系统服务？（3）景观简化对最终作物生产的连锁效应有多大？
中文摘要
人类对土地的利用威胁着全球生物多样性，损害了对粮食生产至关重要的多种生态系统功能。与作物产量相关的生态系统服务功能是由少数优势物种维持的还是依靠物种的高丰富度至今仍不清楚。本文利用 89 项研究（1475 个地点）的全球数据库，划分了物种丰富度、丰度和优势度对授粉、生物病虫害防治以及土地利用变化背景下的最终产量的相对重要性。传粉媒介和敌人的丰富度直接支持了生态系统服务，并且独立于丰度和优势度。景观简化对生态系统服务的消极影响高达 50% 是由于提供服务的生物体的丰富度损失造成的，这对作物产量产生了消极影响。因此，维持生态系统服务提供者的生物多样性对于维持农业生态系统的关键利益流向社会至关重要。
英文摘要
Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield–related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.
原文信息
Fig. 1 Distribution of analyzed studies and effects of richness on ecosystem services provisioning.
(A) Map showing the size (number of crop fields sampled) and location of the 89 studies (further details of studies are given in table S1). (B) Global effect of pollinator richness on pollination (n = 821 fields of 52 studies). (C) Global effect of natural enemy richness on pest control (n = 654 fields of 37 studies). The thick line in each plot represents the median of the posterior distribution of the model. Light gray lines represent 1000 random draws from the posterior. The lines are included to depict uncertainty of the modeled relationship.
Fig. 2 Direct and indirect effects of richness, total abundance, and evenness on ecosystem services.
(A) Path model of pollinator richness as a predictor of pollination, mediated by pollinator abundance. (B) Path model of natural enemy richness as a predictor of pest control, mediated by natural enemy abundance. (C) Path model of pollinator richness as a predictor of pollination, mediated by pollinator evenness. (D) Path model of natural enemy richness as a predictor of pest control, mediated by natural enemy evenness. Pollination model, n = 821 fields of 52 studies; pest control model, n = 654 fields of 37 studies. Path coefficients are effect sizes estimated from the median of the posterior distribution of the model. Black and red arrows represent positive or negative effects, respectively. Arrow widths are proportional to highest density intervals (HDIs).
Fig. 3 Direct and indirect effects of landscape simplification on richness of service-providing organisms and associated ecosystem services.(A) Path model of landscape simplification as a predictor of pollination, mediated by pollinator richness (n = 821 fields of 52 studies). (B) Path model of landscape simplification as a predictor of pest control, mediated by natural enemy richness (n = 654 fields of 37 studies). Path coefficients are effect sizes estimated from the median of the posterior distribution of the model. Black and red arrows represent positive and negative effects, respectively. Arrow widths are proportional to HDIs. Gray arrows represent nonsignificant effects (HDIs overlapped zero).
Fig. 4 Direct and cascading effects of landscape simplification on final crop production via changes in richness, evenness, and ecosystem services.
(A) Path model representing direct and indirect effects of landscape simplification on final crop production through changes in pollinator richness, evenness, and pollination (n = 438 fields of 27 studies). (B) Path model representing direct and indirect effects of landscape simplification on final crop production through changes in natural enemy richness, evenness, and pest control [only insecticide-free areas were considered in the model (n = 185 fields of 14 studies)]. Path coefficients are effect sizes estimated from the median of the posterior distribution of the model. Black and red arrows represent positive and negative effects, respectively. Arrow widths are proportional to HDIs. Gray arrows represent nonsignificant effects (HDIs overlapped zero).
小编：王丹
中国农业大学土地科学与技术学院