A Comparative Analysis of Evenness Index Sensitivity

Abstract

Evenness indices are numerous but the lack of knowledge of their properties is a limitation to their biological usefulness. 15 evenness indices, two of them being recently proposed, were studied in this work. We investigated the sensitivity of each index using (1) 189 macroinvertebrate communities sampled in the field, and (2) a set of communities modified in a controlled way.There is no single way to measure evenness. We demonstrated that a measure should be chosen considering (1) the kind of data analysed and, (2) the index properties wanted by users. Depending on the ecological data set the index should be more sensitive to variations in rare, median or abundant species. For most of macroinvertebrate community analyses, a convenient evenness index requirs to be symmetric, unsensitive to variation on rare taxa, with a large range of variation and can be compared with a diversity index. Depending on diversity measure used, five indices correspond to these criteria: E Pielou , E Hurlbert, E -ln(D) , E 1-D, E MI. Our results were summarized in a table which may help users to select a convenient evenness measure according to their specific data. Concerning index properties, three main features that an evenness index should meet are briefly discussed: dependence with richness, symmetry criteria and variation range. A revue of this controversial subject allowed a best understanding of values obtained with evenness measures depending on their own features.

Visual censuses around drifting fish aggregating devices (FADs): a new approach for assessing the diversity of fish in open-ocean waters

“…We considered 2 indices of evenness (Table 1). The Heip's evenness index (E Heip ) (Heip 1974) was computed because it is assumed to be mainly sensitive to variation in rare species (Beisel et al 2003) and is less sensitive to variation in the number of species (Smith & Wilson 1996) than the most widely used even-ness index, the Pielou index (J '), which is also based on the Shannon-Wiener index (H ') (Shannon & Weaver 1949). Complementary to the Heip index, we computed the Berger Parker index (d) (Berger & Parker 1970) because it is only sensitive to variations in the most dominant species.…”

O que ganhamos 'confundindo' riqueza de espécies e equabilidade em um índice de diversidade?

“…No eixo das abscissas poderíamos colocar a riqueza observada (ou um índice de riqueza, ou riqueza rarefeita para um dado tamanho amostral). No eixo das ordenadas poderíamos colocar uma das muitas medidas de equabilidade disponíveis (veja fórmulas em Smith & Wilson 1996, Beisel et al 2003, Mendes et al 2008). Neste tipo de representação, poderíamos distinguir rapidamente, por exemplo, comunidades ricas e ou com alta equabilidade.…”

“…Entretanto, quando se pretende modelar diversidade como resposta a um ou vários preditores (e.g., Modelos Lineares tais como Regressão e Anova), os diagramas apresentados serão de pouca validade. Nestes casos, uma sugestão é modelar separadamente riqueza de espécies e um índice de equabilidade adequado (por exemplo que seja independente da riqueza de espécies; ver várias opções em Smith & Wilson 1996, Beisel et al 2003, Mendes et al 2008). Estas duas métricas medem aspectos distintos da comunidade (Wilsey et al a mesma abundância (ou de forma genérica, importância), a curva resultante será invariável e assumirá o valor do número de espécies (Hill 1973).…”

Study of roadside weed diversity along the constructed and non constructed roads in Palghar, Maharashtra, India.

“…A single diversity index is insufficient to describe community structure of vegetation over a large range (Beisel et al, 2003), hence four different indices were used to interpret the diversity along the surveyed roads. Species richness index (McIntosh, 1967) was used as it provides a quantitative, comparable measure for diversity of an area.…”