Functional biodiversity of macroinvertebrate assemblages along major ecological gradients of boreal headwater streams

1. Biodiversity–environment relationships are increasingly well‐understood in the context of species richness and species composition, whereas other aspects of biodiversity, including variability in functional diversity (FD), have received rather little rigorous attention. For streams, most studies to date have examined either taxonomic assemblage patterns or have experimentally addressed the importance of species richness for ecosystem functioning. 2. I examined the relationships of the functional biodiversity of stream macroinvertebrates to major environmental and spatial gradients across 111 boreal headwater streams in Finland. Functional biodiversity encompassed functional richness (FR – the number of functional groups derived from a combination of functional feeding groups and habit trait groups), FD – the number of functional groups and division of individuals among these groups, and functional evenness (FE – the division of individuals among functional groups). Furthermore, functional structure (FS) comprised the composition and abundance of functional groups at each site. 3. FR increased with increasing pH, with additional variation related to moss cover, total nitrogen, water colour and substratum particle size. FD similarly increased with increasing pH and decreased with increasing canopy cover. FE decreased with increasing canopy cover and water colour. Significant variation in FS was attributable to pH, stream width, moss cover, substratum particle size, nitrogen, water colour with the dominant pattern in FS being related to the increase of shredder‐sprawlers and the decrease of scraper‐swimmers in acidic conditions. 4. In regression analysis and redundancy analysis, variation in functional biodiversity was not only related to local environmental factors, but a considerable proportion of variability was also attributable to spatial patterning of environmental variables and pure spatial gradients. For FR, 23.4% was related to pure environmental effects, 15.0% to shared environmental and spatial effects and 8.0% to spatial trends. For FD, 13.8% was attributable to environmental effects, 15.2% to shared environmental and spatial effects and 5% to spatial trends. For FE, 9.0% was related to environmental variables, 12.7% to shared effects of environmental and spatial variables and 4.5% to spatial variables. For FS, 13.5% was related to environmental effects, 16.9% to shared environmental and spatial effects and 15.4% to spatial trends. 5. Given that functional biodiversity should portray variability in ecosystem functioning, one might expect to find functionally rather differing ecosystems at the opposite ends of major environmental gradients (e.g. acidity, stream size). However, the degree to which variation in the functional biodiversity of stream macroinvertebrates truly portrays variability in ecosystem functioning is difficult to judge because species traits, such as feeding roles and habit traits, are themselves strongly affected by the habitat template. 6. If functional characteristics show strong responses to natural environmental gradients, they also are likely to do so to anthropogenic environmental changes, including changes in habitat structure, organic inputs and acidifying elements. However, given the considerable degree of spatial structure in functional biodiversity, one should not expect that only the local environment and anthropogenic changes therein are responsible for this variability. Rather, the spatial context, as well as natural variability along environmental gradients, should also be explicitly considered in applied research.     

早竹林内蝇类多样性动态及其影响因子分析

【目的】早竹是一种重要的笋用竹种,人工经营的早竹林出笋率高、经济价值大。然而一些蝇类寄生于早竹笋内,导致竹笋品质降低、竹林退笋率增加。通过研究早竹林内蝇类种群动态和物种多样性,为科学防治笋蝇提供依据,以降低早竹笋的退笋率,增加竹笋产量,提高早竹种植的经济效益。【方法】采用黄板诱捕法调查早竹林内蝇类的多样性,运用多元线性回归分析了环境因子对蝇类Shannon-Wiener多样性指数的影响;并使用变异分解的方法分析了空间变量和环境变量对蝇类β多样性的影响。【结果】研究结果显示:在早竹林内共诱捕到的蝇类有8科10种,其中竹笋绒茎蝇Chyliza bambusae、江苏泉蝇Pegomyia kiangsuensis、横带花蝇Anthomyia illocata、常齿股蝇Hydrotaea dentipes、黑带食蚜蝇Episyrphus balteata是早竹林内的优势物种;黄板周围1.5 m范围内成竹数量和幼笋数量对蝇类的多样性有显著性影响,早竹林内蝇类的物种多样性随着成竹数量的增加而降低;空间变量单独对蝇类β多样性的解释量为8.54%,环境变量单独解释的量为28.84%,两者共同解释的量为10.46%,不能被环境变量和空间变量解释的量为52.16%。【结论】本研究展示了早竹林内蝇类多样性变动的动态,并阐释了蝇类多样性的主要影响因子,对于竹林害虫的综合治理、提高竹笋产量具有现实和理论意义。     

Partitioning diversity for conservation analyses

Aim  Differentiation of sites or communities is often measured by partitioning regional or gamma diversity into additive or multiplicative alpha and beta components. The beta component and the ratio of within-group to total diversity (alpha/gamma) are then used to infer the compositional differentiation or similarity of the sites. There is debate about the appropriate measures and partitioning formulas for this purpose. We test the main partitioning methods, using empirical and simulated data, to see if some of these methods lead to false conclusions, and we show how to resolve the problems that we uncover.
Location  South America, Ecuador, Orellana province, Rio Shiripuno.
Methods  We construct sets of real and simulated tropical butterfly communities that can be unambiguously ranked according to their degree of differentiation. We then test whether beta and similarity measures from the different partitioning approaches rank these datasets correctly.
Results  The ratio of within-group diversity to total diversity does not reflect compositional similarity, when the Gini–Simpson index or Shannon entropy are used to measure diversity. Additive beta diversity based on the Gini–Simpson index does not reflect the degree of differentiation between N sites or communities.
Main conclusions  The ratio of within-group to total diversity (alpha/gamma) should not be used to measure the compositional similarity of groups, if diversity is equated with Shannon entropy or the Gini–Simpson index. Conversion of these measures to effective number of species solves these problems. Additive Gini–Simpson beta diversity does not directly reflect the differentiation of N samples or communities. However, when properly transformed onto the unit interval so as to remove the dependence on alpha and N , additive and multiplicative beta measures yield identical normalized measures of relative similarity and differentiation.     

刈割与施肥干扰下高寒草甸植物功能性状的构建模式

针对目前关于植物群落功能性状构建模式及其驱动因素存在的争议, 研究了33个物种10个功能性状的构建模式。研究结果显示: (1)在刈割-施肥复合梯度上, 这些功能性状主要表现为随机构建模式, 发生随机性和确定性构建的样方比例分别为82.7%和17.3%; (2)在10个功能性状中, 生长型、生活周期、单株地上干质量、叶面积和叶干质量5个功能性状为随机构建模式, 不受试验处理和群落特征(地上净初级生产力、刈割生物量损失、群落高度)变化的影响。植物倾斜度、繁殖方式、固氮性、株高和比叶面积5个功能性状的构建模式与试验处理或群落特征变化有关, 表现出趋同或趋异构建响应。其中, 植物倾斜度和比叶面积的构建模式仅受群落特征影响, 而固氮性、繁殖方式和株高3个性状的构建模式同时还受刈割或施肥处理的影响, 其构建模式因功能性状而异; (3)群落的生物量损失和地上净初级生产力是解释植物功能性状构建模式变化较理想的群落特征; (4)刈割和施肥处理对株高的构建模式具有相反效应, 而刈割和施肥的交互作用对其无显著影响。上述结果说明该研究群落植物功能性状的构建存在不同模式, 以随机构建模式为主, 确定性构建模式居次要地位。确定性构建模式与试验处理和群落特征变化有关, 而且是性状依赖的。相反选择力对趋同和趋异构建模式的平衡效应能引起功能性状发生随机构建。     

Characterising functional trait diversity and trait–environment relationships in fish assemblages of boreal lakes

1. Characterisation of biodiversity is typically based on taxonomic approaches, while much less is known about other related aspects. Functional trait diversity is one such component of biodiversity that has not been addressed rigorously in ecological research until recently. We tested the congruence between taxonomic‐ and trait‐based approaches, and examined how spatial configuration, local abiotic environmental factors and biotic effects interact to influence taxonomic‐ and trait‐based characterisation of freshwater fish assemblages. 2. Fish assemblage data were compiled for 124 lakes in southern Finland. Variance partitioning in both linear regression analyses and redundancy analysis was used to quantify the relative contribution of spatial and environmental variables to taxonomic and functional trait diversity and structure. Additionally, a null model analysis was used to test for the potential effects of interspecific segregation and biotic interactions on the co‐occurrence of species. 3. The species pool was relatively poor. However, trait‐based classification of species indicated that most species belonged to unique functional entities, which suggested low redundancy in species composition. Correlation analysis indicated a very strong relationship between species richness (SR) and the number of unique trait combinations (UTC). Ecoregion‐level heterogeneity in SR and UTC were well represented in a relatively small group of randomly selected lakes (c. 30 lakes). Multiple regressions indicated moderate roles for abiotic environmental variables (i.e. lake surface area, depth, total phosphorous, colour and pH) in determining SR, UTC and the distribution of single trait categories, whereas geographical location was not generally influential. 4. Redundancy analysis revealed similar patterns to those of diversity analyses for taxonomic and associated trait‐based structure, emphasising the effect of abiotic environmental variables and the negligible effect of geographical position. 5. Co‐occurrence analysis indicated significant checkerboard distribution at the whole assemblage level, but interspecific segregation proved to be of relatively minor importance in the constrained analyses, where species pair combinations within trait category groups were evaluated. 6. Our results suggest that taxonomic‐ and trait‐based patterns of boreal lake fish assemblages are strongly interrelated. Environmental filtering through the effects of local abiotic variables seems to have the most prominent role in determining trait‐based assemblage patterns among lakes, which may also be secondarily shaped by biotic interactions. 7. From the applied perspective, it may not necessarily matter whether traditional taxonomic or more novel trait‐based approaches are used in characterising spatial patterns in boreal fish assemblages. However, trait‐based approaches may provide complementary information which cannot be directly revealed by taxonomic data.     

中国典型森林生态系统乔木层群落物种多样性的空间分布格局及其影响因素

物种多样性地理分布格局及其成因是生物地理学和宏观生态学研究的核心问题之一,基于中国13个典型森林生态系统乔木层群落植物的调查数据,分析物种多样性随经纬度的变化规律,探讨物种多样性空间分布格局的影响因素。结果表明:(1) 13个典型森林生态系统的4个物种多样性指数均随经纬度上升而下降,其中物种丰富度变化更为显著,而Shannon-Wiener指数、Simpson指数和Pielou指数随经度上升变化不显著;(2)相关性分析结果显示,物种多样性指数与植物特性、能量和水分因子的单因素相关关系并不一致。其中,物种丰富度、Shannon-Wiener指数和Simpson指数与年均温、最冷月均温、温度年较差和潜在蒸散量的相关性最显著(P0.01),Pielou指数与年均温、最冷月均温、实际蒸散量、潜在蒸散量和郁闭度有显著相关关系(P0.05);(3)方差分解结果表明,能量和水分的共同作用对物种多样性指数空间分布格局的解释率最高,达到15%—42%;植物特性、能量和水分因子三者共同作用对物种多样性指数空间分布格局解释率次之,为14%—27%;植物特性与能量因子或水分因子两者之间的共同作用以及植物特性和水分因子独立作用对物种多样性指数空间分布格局的解释率较小,其中能量因子对物种多样性指数空间分布格局的单独解释率高于植物特性或水分因子。研究表明能量和水分共同作用是影响大尺度森林乔木层物种多样性空间分布格局形成的主要因素,但植物特性的差异对物种多样性空间分布格局影响也不可忽视。