Lognormal Distributions and the Concept of Community Equilibrium

Ugland, Karl I.; Gray, John S.

doi:10.2307/3544482

Cited by 139 publications

(126 citation statements)

References 13 publications

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“…Uma das possíveis vantagens de índices de diversidade paramétricos é que algumas distribuições são embasadas por teorias de como as espécies partilham os recursos disponíveis. O ajuste dos dados a uma certa distribuição possibilitaria, portanto, interpretações ecológicas (Ugland & Gray 1982, Tokeshi 1993. Apesar da aparente vantagem de tais índices paramétricos, muitos conjuntos de dados são bem ajustados por mais de um tipo de distribuição de abundância relativa (Cielo Filho et al 2002).…”

Section: Desvantagensunclassified

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

Melo

2008

Biota Neotrop.

141

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MELO, A.S. What do we win 'confounding' species richness and evenness in a diversity index? Biota Neotrop., 8(3): http://www.biotaneotropica.org.br/v8n3/en/abstract?point-of-view+bn00108032008. Abstract:In Community Ecology and in many applications of Conservation Biology, diversity means variety of species, which may or not include information on the relative importance of each species. Diversity is one of the most important attributes in the study of communities and, as a result, many methods are available to its measurement. Among them, non-parametric diversity (or heterogeneity) indices such as Shannon and Simpson formulae are widely employed in a range of studies. These indices are composed of (or confound) two components, species richness and evenness. Different indices can be obtained combining the two components with different weights. The lack of an objective criteria to guide appropriate weighting of each component results in an arbitrary decision to use an index and not another. Additionally, depending on the weight the indices give to each component, an index may indicate that community A is more diversified than community B while a second index may indicate the contrary. Also, diversity indices applied to samples differing in species richness and evenness may produce similar values. Such problems can be avoided using alternative methods. One of them is diversity profile, which includes not one index but many diversity indices differing in the weight given to each component. Additional alternatives include the use of species richness only, Whittaker's diagram (or of dominance) and scatter diagrams with axes defined by species richness and an evenness index. Except by species richness, the cited alternative methods show graphically much more information than that contained in a single value produced by a diversity index. In studies requiring a response variable to be modeled in relation to predictor variables (Linear Models such as Regression and Analysis of Variance), I suggest the separate use of species richness and evenness as each one may reflect different aspect of communities. Resumo: No contexto de Ecologia de Comunidades e em várias aplicações da Biologia da Conservação, diversidade indica variedade de espécies, podendo ou não incluir informações sobre a importância relativa de cada espécie. Diversidade é um dos atributos mais fundamentais no estudo de comunidades e para tal uma ampla gama de métodos para sua mensuração estão disponíveis. Entre eles destacam-se, pelo amplo uso, índices de diversidade não-paramétricos (ou de heterogeneidade) tais como os Índices de Shannon e Simpson. Estes índices consistem de (ou confundem) dois componentes, riqueza de espécies e equabilidade. Diferentes índices de diversidade podem ser obtidos combinando-se com diferentes pesos estes dois componentes. Dada a ausência de um critério objetivo na escolha destes pesos, o uso de um índice em detrimento de outro é muitas vezes arbitrário. Adicionalmente, visto o peso dado por cada índice de diversidade para cada u...

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Section: Desvantagensunclassified

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

Melo

2008

Biota Neotrop.

141

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“…An appropriate model is perhaps that most of these species are rare (Ugland & Gray 1982) and that mortahty, induced by drill-cutting discharges, leads to local extinctions. Thus, there are vacant niches which are initially colonised in a random fashion leading to an increase in species number.…”

Section: Discussionmentioning

confidence: 99%

Detection of initial effects of pollution on marine benthos: an example from the Ekofisk and Eldfisk oilfields, North Sea

Gray¹,

Clarke²,

Warwick³

et al. 1990

Mar. Ecol. Prog. Ser.

377

235

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Reductions in number of species and diversity and increased dominance of opportunistic species occurred late in the sequence of response to oil as a stress factor (within 500 to 1000 m of discharge sources). However, multivariate analyses, (classification analysis using the Bray-Curtis dissimilarity index) and ordination (multi-dimensional scaling) clearly distinguished site groupings related to oil activities at distances of up to 2 to 3 km from the Ekofisk pollution source and up to 1.5 km from the Eldfisk source. The first recorded changes in benthic communities in response to oil were increased abundance patterns of some species and changes in the presence and absence patterns of rare species, with species being mostly present in one site group and mostly absent in another site group. Only under severe pollution did the opportunistic species, which have often been suggested as universal indicators of pollution, dominate. The major site groupings could still be distinguished after aggregation to higher taxa (families and even phyla) when using multivariate analyses. If this finding proves to be a general one then great savings in time and effort, with little or no loss of precision, wdl be possible in environmental monitoring.

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“…that caused by low-level pollution (Gray & Mirza 1979, Ugland & Gray 1982. The degree of evenness, or relative dominance, in species' abundances in particular is considered a useful and sensitive indicator of disturbance in marine benthic communities ).…”

Section: Sieve Size In Relation To Estimating Species Richness Divermentioning

confidence: 99%

Sieve size influence in estimating biomass, abundance and diversity in samples of deep-sea macrobenthos

Gage¹,

Hughes²,

Vecino³

2002

Mar. Ecol. Prog. Ser.

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A divergence in sieve size protocols for washing samples has arisen among shallow-and deep-sea benthic biologists, which now affects comparability across the 2 environments. This has come about as a result of a perception of smaller body size among deep-sea benthic organisms. Two box-core samples from ~1900 m depth were examined to see how different sieve size affects estimation of biomass, abundance and diversity of macrofauna in the deep sea. Expressed as cumulative retentions, the coarsest sieve (1 mm mesh) retained 94% of the biomass retained in the finest sieve (0.25 mm), confirming the expectation that rarer, large-sized individuals contribute most to biomass of macrobenthos. There were small increases when progressively finer sieves were used, but the rate of increase declined markedly from 0.425 to 0.25 mm mesh. Numbers of individual organisms increased through the series, with a marked increase from 0.5 to 0.425 mm mesh; numbers of species did not increase as rapidly, but showed a similarly high rate between 0.5 and 0.425 mm mesh. The proportions of the total biomass in coarser sieves, and the total number of specimens retained by the finest sieve were rather similar to those shown in previous studies of inshore and continental shelf benthos. However, the retention of deep-sea species by the 0.5 mm sieve (86%) was about the same as the percentage of inshore species retained by the 1.0 mm sieve (at this sieve size only 54% of deepsea species were retained). Although the finer sieves in both shallow-and deep-sea samples include many postlarval stages, this differing response for species must reflect smaller size of some adult macrobenthos in the deep sea. The effect on diversity depended on index used, with Shannon's index increasing down to the 0.5 mm mesh, but showing a variable response in the finer sieves. This probably mostly reflects increased retention of small-sized juveniles of species already retained, causing increasing unevenness in species abundances with smaller sieve size, rather than addition of smallsized species not previously retained in coarser sieves. Expected numbers of species calculated by rarefaction seems much less affected, with the degree of overlap of rarefaction curves reflecting relative similarity in distribution of species abundances. Degree of overestimation (of expected number of species against number of individuals along the curve) is greatest for the 1 mm mesh, even if the end-points of the curve show decreasing disparity, from 1 to 0.25 mm mesh, in total retention of species as well as individuals. It is argued that, as would apply in shallow water, the great dependence of evenness on sieve size makes shifts in distribution of species abundances caused by disturbance more difficult to detect against the baseline, unless a sufficiently small sieve has been used. When sieve retention was separately considered for the major taxonomic groups of macrobenthos (Polychaeta, Peracarida, Mollusca), differing patterns in relation to sieve size were found in terms of a...

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Lognormal Distributions and the Concept of Community Equilibrium

Cited by 139 publications

References 13 publications

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

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

Detection of initial effects of pollution on marine benthos: an example from the Ekofisk and Eldfisk oilfields, North Sea

Sieve size influence in estimating biomass, abundance and diversity in samples of deep-sea macrobenthos

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