Negative relationships between species richness and evenness render common diversity indices inadequate for assessing long-term trends in butterfly diversity

Species richness and evenness, the two principle components of species diversity, are frequently used to describe variation in species assemblages in space and time. Compound indices, including variations of both the Shannon–Wiener index and Simpson’s index, are assumed to intelligibly integrate species richness and evenness into all-encompassing measures. However, the efficacy of compound indices is disputed by the possibility of inverse relationships between species richness and evenness. Past studies have assessed relationships between various diversity measures across survey locations for a variety of taxa, often finding species richness and evenness to be inversely related. Butterflies are one of the most intensively monitored taxa worldwide, but have been largely neglected in such studies. Long-term butterfly monitoring programs provide a unique opportunity for analyzing how trends in species diversity relate to habitat and environmental conditions. However, analyzing trends in butterfly diversity first requires an assessment of the applicability of common diversity measures to butterfly assemblages. To accomplish this, we quantified relationships between butterfly diversity measures estimated from 10 years of butterfly population data collected in the North Saskatchewan River Valley in Edmonton, Alberta, Canada. Species richness and evenness were inversely related within the butterfly assemblage. We conclude that species evenness may be used in conjunction with richness to deepen our understandings of assemblage organization, but combining these two components within compound indices does not produce measures that consistently align with our intuitive sense of species diversity.     

Species richness and evenness respond in a different manner to propagule density in developing prairie microcosm communities

Diversity has two basic components: richness, or number of species in a given area, and evenness, or how relative abundance or biomass is distributed among species. Previously, we found that richness and evenness can be negatively related across plant communities and that evenness can account for more variation in Shannon’s diversity index (H′) than richness, which suggests that relationships among diversity components can be complex. Non-positive relationships between evenness and richness could arise due to the effects of migration rate or local species interactions, and relationships could vary depending on how these two processes structure local communities. Here we test whether diversity components are equally or differentially affected over time by changes in seed density (and associated effects on established plant density and competition) in greenhouse communities during the very early stages of community establishment. In our greenhouse experiment, we seeded prairie microcosms filled with bare field soil at three densities with draws from a mix of 22 grass and forb species to test if increased competition intensity or seedling density would affect the relationships among diversity components during early community establishment. Increased seed density treatments caused diversity components to respond in a different manner and to have different relationships with time. Richness increased linearly with seed density early in the experiment when seedling emergence was high, but was unrelated to density later in the experiment. Evenness decreased log-linearly with seed densities on all sampling dates due to a greater dominance by Rudbeckia hirta with higher densities. Early in the experiment, diversity indices weakly reflected differences in richness, but later, after the competitive effects of Rudbeckia hirta became more intense, diversity indices more strongly reflected differences in evenness. This suggests that species evenness and diversity indices do not always positively covary with richness. Based on these results, we suggest that evenness and richness can be influenced by different processes, with richness being more influenced by the number of emerging seedlings and evenness more by species interactions like competition. These results suggest that both diversity components should be measured in plant diversity studies whenever it is possible.     

新薛河底栖动物物种多样性与功能多样性研究

研究功能多样性与物种多样性关系及其随环境梯度的变化规律,有助于理解生物在群落中的共存机制;然而,二者间关系的研究在淡水生态学中尚鲜见报道。通过对新薛河典型河段(A缓流河段、B断流河段、C有机污染河段、D对照河段、E人为干扰河段)底栖动物季节性调查,就物种多样性和功能多样性时空动态及关系进行了研究。结果表明:在空间序列上,物种多样性指数在B河段均最低,表明间歇性断流对物种多样性影响重大。功能丰富度在D河段最高,A河段最低;功能均匀度在A河段高于其他河段;功能分离度在A、B河段最高,D河段最低。在时间序列上,物种丰富度和Shannon指数均值在10月份最低,4月份最高;均匀度指数在12月份最低,10月份最高。3个功能多样性指数于各季节间差异显著、相互独立,主要受水文条件和底栖动物生活史影响。相关分析表明,功能多样性指数间无显著相关性;功能丰富度同物种丰富度和Shannon指数相关显著,功能均匀度同物种均匀度相关显著。逐步回归分析发现,功能丰富度受物种丰富度和Shannon指数影响显著,功能均匀度受物种均匀度影响显著;功能多样性和物种多样性指数间拟合度总体不高。研究结果进一步表明:相对物种多样性,功能多样性对生境梯度变化响应更加全面。     

From plots to islands: species diversity at different scales

Aim To investigate how plant diversity of whole islands (‘gamma’) is related to alpha and beta diversity patterns among sampling plots within each island, thus exploring aspects of diversity patterns across scales. Location Nineteen islands of the Aegean Sea, Greece. Methods Plant species were recorded at both the whole‐island scale and in small 100 m² plots on each island. Mean plot species richness was considered as a measure of alpha diversity, and six indices of the ‘variation’‐type beta diversity were also applied. In addition, we partitioned beta diversity into a ‘nestedness’ and a ‘replacement’ component, using the total species richness recorded in all plots of each island as a measure of ‘gamma’ diversity. We also applied 10 species–area models to predict the total observed richness of each island from accumulated plot species richness. Results Mean alpha diversity was not significantly correlated with the overall island species richness or island area. The range of plot species richness for each island was significantly correlated with both overall species richness and area. Alpha diversity was not correlated with most indices of beta diversity. The majority of beta diversity indices were correlated with whole‐island species richness, and this was also true for the ‘replacement’ component of beta diversity. The rational function model provided the best prediction of observed island species richness, with Monod’s and the exponential models following closely. Inaccuracy of predictions was positively correlated with the number of plots and with most indices of beta diversity. Main conclusions Diversity at the broader scale (whole islands) is shaped mainly by variation among small local samples (beta diversity), while local alpha diversity is not a good predictor of species diversity at broader scales. In this system, all results support the crucial role of habitat diversity in determining the species–area relationship.     

Functional richness, functional evenness and functional divergence: the primary components of functional diversity

Functional diversity is hypothesised as being beneficial for ecosystem functions, such as productivity and resistance to invasion. However, a precise definition of functional diversity, and hence a framework for its quantification, have proved elusive. We present a definition based on the analogy of the components of species diversity – richness, evenness and divergence. These concepts are applied to functional characters to give three components of functional diversity – functional richness, functional evenness and functional divergence. We demonstrate how each of these components may be calculated. It is hoped that our definition of functional diversity and its components will aid in elucidation of the mechanisms behind diversity/ecosystem-function relationships.     

山西七里峪茶条槭群落特征及物种多样性研究

运用TWINSPAN对山西七里峪茶条槭群落类型进行划分,并采用Patrick指数、Simpson指数、Shannon-Wiener指数、Alatalo指数研究群落的物种多样性。结果表明:TWINSPAN将茶条槭群落的73个样方划分为10个群丛;各群丛的物种丰富度指数、多样性指数和均匀度指数之间存在差异,群丛Ⅲ和Ⅶ的丰富度指数和多样性指数较高,群丛Ⅰ的多样性指数较低;各群丛乔木层、灌木层和草本层之间的物种多样性也存在差异,多样性指数大致表现为草本层高于灌木层高于乔木层。土壤中的有机质、速效钾、含水量是影响茶条槭群落物种多样性的主要因素。     

Functional regularity: a neglected aspect of functional diversity

Functional diversity has been identified as a key to understanding ecosystem and community functioning. However, due to the lack of a sound definition its nature and measurement are still poorly understood. In the same way that species diversity can be split into species richness and species evenness, so functional diversity can be split into functional richness (i.e. the amount of functional trait/character/attribute space filled) and functional evenness (i.e. the evenness of abundance distribution in functional trait space). We propose a functional regularity index (FRO) as a measure of functional evenness for situations where species are represented only by a single functional trait value (e.g. mean, median or mode), and species abundances are known. This new index is based on the Bulla O index of species evenness. When dealing with functional types or categorical functional traits, the Bulla O or any other accepted species evenness index may be used directly to measure functional evenness. The advantage of FRO is that it supplies a measure of functional evenness for continuous trait data. The FRO index presented in this paper fulfils all the a priori criteria required. We demonstrate with two example datasets that a range of FRO values may be obtained for both plant and animal communities. Moreover, FRO was strongly related to ecosystem function as seen in photosynthetic biomass in plant communities, and was able to differentiate sampling stations in a lagoon based on the functional traits of fish. Thus, the FRO index is potentially a highly useful tool for measuring functional diversity in a variety of ecological situations.     

鼎湖山植物群落多样性的研究

根据鼎湖山自然保护区１６个植物群落的样地调查资料,从种丰富度和不同类型的物种多样性指数、均匀度与植被类型、人为干扰程度、演替阶段等方面的关系进行了分析。本区植被类型的多样性指数、均匀率指数变化反映了其结构复杂程度、生境的差异。物种丰富和多样性随着人为干扰程度的增强而降低。群落内各层的物种丰富度的大小的顺序为“灌木层＞草本层＞乔木层”,而群落多样性指数的大小顺序为“灌木层＞乔木层＞草本层”。群落多样     

山西五鹿山森林群落木本植物功能多样性

通过选取群落中木本植物种子的扩散方式、传粉方式、植株高度和盖度等13个功能性状,计算出群落的6个功能多样性指数:功能性状距离、功能性状平均距离、功能体积、功能均匀度、功能分散指数和Rao二次熵指数,结合群落物种丰富度指数、Shannon-Wiener指数和物种均匀度指数对山西五鹿山森林群落木本植物功能多样性进行研究。结果表明:(1)功能性状距离、功能性状平均距离、功能体积与物种丰富度、Shannon-Wiener指数显著正相关;功能均匀度与Shannon-Wiener指数、物种均匀度指数显著正相关;功能分散指数、Rao二次熵指数与物种均匀度指数、Shannon-Wiener指数显著正相关;(2)功能多样性的差异很大程度上是由于物种差异所引起的;(3)6个功能多样性指数可分为三类:功能性状距离、功能性状平均距离、功能体积为功能丰富度指数;功能均匀度为功能均匀度指数;功能分散指数和Rao二次熵指数为功能离散度指数。该分类结果符合指数的计算方法和生态学意义,以及相互独立的标准。     

Diversité spécifique et évolution des groupements végétaux supra forestiers des Pyrenèes centrales

Summary Calculations of various diversity indices in seral meadow communities from the Central Pyrenees subalpine zone were based on quantitative vegetational analyses by the point quadrat method. Species richness (S) increased rapidly toward a maximum then decreased markedly with increasing maturation of the meadows. In contrast, equitability measured as the Pielou index first inereases gradualy and then remains on more or less the same level, while decreasing a little in older stages, if not accelered by over-grazing. Not surprisingly, Patten's redundancy measure exibits inverse variations. Since it encompasses both the number of species and the distribution of individuals over the species, the Shannon and Weaver index of diversity behaved in a manner intermediate between richness and evenness. In the two toposequences investigated, diversity and equitability variations were highly correlated with the occurence of monopolistic dominant species.

Nom des plantes suivant P. Fournier (1961) Les quatre flores de France.     

高寒草地植物物种多样性与功能多样性的关系

物种多样性与功能多样性的关系是生态学当前研究的热点问题之一,不同区域典型生态系统物种多样性和功能多样性的关系研究有利于生物多样性保护理论的全面发展。以青藏高原地区的主要草地生态系统—高寒草甸和高寒草原为研究对象,采用4个物种多样性指数(Patrick丰富度指数、Shannon-Weiner多样性指数、Pielou均匀度指数和Simpson优势度指数)和9个功能多样性指数(FAD功能性状距离指数、MFAD功能性状平均距离指数、基于样地的FDp和基于群落的FDc功能树状图指数、FRic功能体积指数、FEve功能均匀度指数、Rao功能离散度常二次熵指数、FDiv功能离散指数、FDis功能分散指数),分析了高寒草地植物物种多样性、功能多样性关系及其与初级生产力的关系,以期阐明3个科学问题:不同草地类型的高寒草地生态系统植物物种多样性和功能多样性有何差异?高寒草地生态系统的植物物种多样性和功能多样性有何关系?高寒草地生态系统物种多样性、功能多样性对生态系统功能的影响有何异同?研究结果表明:(1)与高寒草原相比,高寒草甸具有更高的物种多样性、功能丰富度和功能离散度;(2)高寒草甸中,Patrick丰富度与功能丰富度指数(FAD、MFAD、FDp、FDc)和功能离散度指数(FDiv)的具有较强的相关性,最优拟合方程分别为幂函数和二次多项式函数;(3)高寒草原中,Patrick丰富度与功能丰富度指数(FAD、MFAD、FDp、FDc、FRic)、Shannon指数和Simpson指数与FEve指数的相关性较强,最优拟合方程为二次多项式函数,Pielou指数与FEve指数的相关性较强,最优拟合方程为指数函数;(4)高寒草甸的初级生产力分别与物种丰富度指数Patrick、功能离散指数FDiv具有较强的相关性;而高寒草原的初级生产力与4个物种多样性指数间均具有较强的相关性,与功能离散指数FDiv具有较强的相关性,最佳拟合方程均为二次多项式函数。研究的总体结论为:物种多样性、功能多样性、二者之间的关系以及二者与生态系统服务功能(以初级生产力为例)之间的关系在高寒草甸和高寒草原群落中表现迥异,因此在研究青藏高原高寒草地的生态功能时,不能仅仅测度传统的物种多样性,还应测度与物种多样性、生态功能密切相关的功能多样性。     

北京东灵山地区植物群落多样性的研究Ⅱ丰富度、均匀度和物种多样性指数

本文以１２５块植物群落调查样地资料为基础,从不同类型、层次的丰富度、均匀度和物种多样性指数及其与海拔的关系等方面对东灵山地区植物群落多样性进行了分析。本区亚高山草甸植物群落多样性沿海拔梯度的变化规律是：物种丰富度和物种多样性指数随海拔升高而下降;物种均匀度则随海拔升高而增加。植物生长型与群落多样性指数的关系表现为“乔木层、灌木层物种丰富度指数相近且明显低于草本层;灌木层和草本层的均匀度指数相近,群落间变异幅度较小,乔本层则变异幅度很大;物种多样性指教则表现出草本层＞乔本层＞灌木层的规律。物种盖度和地上生物量作为测度指标计算群落多样性所得结果相近,且优于以株数作为测度指际计算的结果。     

Richness, structure and functioning in metazoan parasite communities

Ecosystem functioning, characterized by components such as productivity and stability, has been extensively linked with diversity in recent years, mainly in plant ecology. The aim of our study was thus to quantify general relationships between diversity, community structure and ecosystem functions in metazoan parasite communities. We used data on parasite communities from 15 species of marine fish hosts from coastal Chile. The volumetric abundance (volume of all parasite species per individual host, in mm³) was used as a surrogate for productivity. Species diversity was measured using both species richness and evenness, while community structure was estimated using the co‐occurrence indices V‐ratio, C‐score and a new C‐score_s index standardized for the number of host replicates. After correcting for fish size, 47% of host species show no relationship, 13% show a hump shaped curve and 40% show positive monotonic relationships between productivity and parasite richness across all host individuals in a sample. We obtained a logarithmically decreasing relationship between evenness and productivity for all fish species, and propose a ‘dominance‐resistance’ hypothesis based on immunity to explain this pattern. The stability of the parasite community, measured as the coefficient of variation in productivity among individual hosts, was strongly and positively related to mean species richness across the 15 host species. The C‐score_s index, based on the number of checkerboard units in the host‐parasite presence/absence matrix, increases linearly with mean productivity across the 15 host species, suggesting that parasite communities tend to be more structured when they are more productive. This is the likely reason why linear relationships between richness and productivity were not observed consistently in all fish species. Parasite communities provide some clear patterns for the diversity–ecosystem functioning debate in ecology, although other factors, such as the history of community assembly, may also influence these patterns.     

Do acoustic indices correlate with bird diversity? Insights from two biodiverse regions in Yunnan Province,south China

Human activities are affecting biodiversity to a greater extent than ever. Consequently, tools that can efficiently monitor changes in communities are becoming increasingly important. In the case of birds and other vocalizing animals, it has been suggested that passive acoustic methods can be used for this purpose. Multiple acoustic indices have been developed recently, to be used as proxies for species diversity. Preliminary results have been promising. Yet, before the indices can be applied widely, it is necessary to understand better how well they reflect the communities to be monitored, and how they perform under diverse environmental conditions. Here, we tested seven of the available indices, on sound recordings made in two biodiverse regions in Yunnan Province, south China. We assessed each index’s performance by measuring its correlation to bird species richness and diversity, estimated using point-count surveys. Each survey was conducted by an expert observer, at the same time each recording was made, and for the same duration. We also tested whether the performance of the indices was affected by levels of environmental dissimilarity between the sites sampled. We found that although no index showed a very strong correlation with species richness or diversity, three indices (the acoustic entropy, acoustic diversity and acoustic evenness indices) performed consistently better that the other four, showing moderate correlations. The levels of environmental dissimilarity among the sites did not seem to affect the performance of any of the indices tested, suggesting consistency − an important property for the indices to have. We conclude that although the acoustic indices have the potential to be used for passive acoustic monitoring, perhaps they need to be refined further before they can be applied widely. Meanwhile, they should be tested in more environments to reveal fully their potential and limitations.     

塔里木荒漠河岸林异质生境物种多样性比较与其测度指标筛选及评价

选择合适的物种多样性测度指标与多样性指数是进行群落多样性研究的基础工作。依据塔里木河上游荒漠河岸林样地调查资料,分别采用重要值、盖度和多度为测度指标比较了反映群落物种丰富度、多样性、均匀度和优势度12种多样性指数与异质生境群落多样性特征,并对多样性指数进行了相关分析与评价。结果表明,荒漠河岸林异质生境群落物种组成种类差异明显,轮南镇胡杨群落物种丰富度与多样性指数最高,水工三连灰胡杨群落多样性最低,土壤水盐的空间异质性是引起荒漠植被空间分布与群落多样性差异的主导因子。表征荒漠群落多样性以重要值和盖度为测度指标优于多度指标,其中以重要值为测度指标来反映群落多样性更为合理。相关与主成分分析表明,均匀度与多样性指数间的相关性高于丰富度与多样性指数,且多样性指数受均匀度、优势度指数受丰富度影响较大,反映出荒漠河岸林群落多样性主要决定于物种分布的均匀程度。12种多样性指数中Margalef丰富度指数（Ma）、Shannon-Weiner多样性指数（H）与Simpson多样性指数（D）能客观真实地反映异质生境荒漠植物群落多样性。同时,针对高度生境异质性的荒漠植物群落,还应综合考虑群落物种组成与生境特征,选择合适的多样性指数组合可更客观地反映荒漠河岸林群落多样性变化。     

山西翅果油树群落的多样性研究

用丰富度指数、多样性指数和均匀度指数对山西翅果油树群落的多样性进行了研究 ,并用相关分析研究了海拔与多样性指数及多样性指数间的关系 ,结果表明 :1 )在干扰强烈的生境中 ,翅果油树群落具有较低的丰富度指数、多样性指数的均匀性 ,而接近顶极群落阶段 ,多样性指数和丰富度指数也较低 ,但具有较高的均匀性 ;干扰强度较小的生境中 ,群落具有较高的丰富度指数、多样性指数和均匀性。2 )灌木层和草本层的丰富度、多样性指数和均匀度指数呈现多元化的趋势。 3)海拔对山西翅果油树群落多样性的影响不显著。     

广西马尾松林植物功能多样性与生产力的关系

探索植物多样性与生产力的关系可为森林经营与管理提供科学基础。本研究以广西4个地区的马尾松(Pinus massoniana)人工林群落为研究对象, 通过计算物种多样性、功能多样性和功能优势值, 运用相关分析、自动线性建模和方差划分等方法, 分析了多样性与生产力的关系。研究发现, 生产力与物种丰富度、Shannon指数、功能丰富度、功能均匀度极显著正相关(P < 0.01), 与物种均匀度、功能多样性、功能离散度、功能团个数、坡向显著正相关(P < 0.05), 与林龄极显著负相关(P < 0.01), 4个功能多样性参数和4个物种多样性参数两两之间皆为显著正相关; 未发现初始生物量制约生产力的提高; 方差划分最优模型中, 功能多样性参数效应、功能优势值效应和林龄效应分别解释生产力方差的56%、43%和33%, 功能多样性参数效应和功能优势值效应重叠部分高达27%; 生态位互补效应主要由功能丰富度和功能均匀度产生, 选择效应主要由生长型优势值产生; 生长型优势值为灌木的样地生产力较高, 次优种或过渡种对生态系统功能也有重要作用。以生产力为响应变量的自动线性建模最佳子集包括重要性由大到小的5个因素: 林龄、生长型优势值、功能丰富度、功能均匀度、功能团个数。建议维护森林功能多样性, 加强林下叶层植物保护, 用好功能重要的物种, 通过林下叶层的补偿性光合作用和生长竞争, 有效地提高生产力和生物多样性。     

Partitioning the diversity of riverine fish: the roles of habitat types and non-native species

1. Quantifying how biological diversity is distributed in the landscape is one of the central themes of conservation ecology. For this purpose, landscape classifications are being intensively used in conservation planning and biodiversity management, although there is still little information about their efficacy. 2. I used data from 158 running water sites in Hungary to examine the contribution of six a priori established habitat types to regional level diversity of fish assemblages. Three community measures [species richness, diversity (Shannon, Simpson indices), assemblage composition] were examined at two assemblage levels (entire assemblage, the native assemblage). The relative role of non‐native species was quantified to examine their contribution to patterns in diversity in this strongly human influenced landscape. 3. Additive diversity partitioning revealed the primary importance of beta diversity (i.e. among‐site factors) to patterns in species richness. Landscape‐scale patterns in species richness were best explained by between‐habitat type (beta₂: 41.2%), followed by within‐habitat type (beta₁: 37.7%) and finally within‐site (alpha: 21.1%) diversity. Diversity indices showed patterns different from species richness, indicating the importance of relative abundance distributions on the results. Exclusion of non‐natives from the analysis gave similar results to the entire‐assemblage level analysis. 4. Canonical analysis of principal coordinates, complemented with indicator species analysis justified the separation of fish assemblages among the habitat types, although classification error was high. Multivariate dispersion, a measure of compositional beta diversity, showed significant differences among the habitat types. Contrary to species diversity (i.e. richness, diversity indices), patterns in compositional diversity were strongly influenced by the exclusion of non‐natives from the analyses. 5. This study is the first to quantify how running water habitat types contribute to fish diversity at the landscape scale and how non‐native species influence this pattern. These results on riverine fish assemblages support the hypothesis that environmental variability (i.e. the diversity of habitat types) is an indication of biodiversity and can be used in large‐scale conservation designs. The study emphasises the joint application of additive diversity partitioning and multivariate statistics when exploring the contribution of landscape components to the overall biodiversity of the landscape mosaic.     

An assessment of the dependence of evenness indices on species richness

Evenness is the component of species diversity that was built to be mathematically independent from species richness. Yet, earlier work questioned the generality of this independence. However, this earlier work involved only a few relative abundance distributions (RADs), very limited gradients of species richness, or evenness indices, such as Pielou's index, that were not defined in relation to a precise, coherent set of axioms. We show that for very different theoretical RADs, a relationship between evenness indices and species richness does exist and is strong-at least for some RADs and/or when species richness is under 20. Furthermore, this relationship is mostly negative, which contradicts some previous studies. We also show that, for the very uneven RADs we tested, evenness indices depend even more on species richness than diversity indices do. Finally, we discuss the philosophy behind the analysis of evenness-richness relationships within and between RADs, as well as the interest of correcting evenness indices for species richness when species richness varies, especially with many values under 20.