Measuring b-diversity using a taxonomic similarity index, and its relation to spatial scale

Abstract

We present a new similarity index, taxonomic similarity (∆ S ), which can be used to measure β-diversity. ∆ S utilises species presence/absence data, and incorporates both higher taxon richness and evenness concepts. It is derived from the average taxonomic distance (relatedness) of any 2 species from different sites. Therefore ∆ S is analogous to taxonomic distinctness recently developed for biodiversity assessment at α-and γ-(landscape or seascape) scales. ∆ S is a new index, although its derivation uses a concept similar to the 'optimal taxonomic mapping statistic' developed independently for quantifying structural redundancy in marine macrobenthos. Using echinoderm data, we show that ∆ S exhibits smoother behaviour and is less influenced by species richness, and hence sampling effort, than the widely used Jaccard coefficient of species similarity. We also believe ∆ S to be a more intuitive and comprehensive measure of similarity than Jaccard and other conventional indices based solely on species held in common. Taxonomic similarity between sites is computed for echinoderms examined over 3 different spatial scales: local/small-scale (<10 km), intermediate-scale (10 to 100s km) and province/oceanic-scale (100s to 1000s km). Taxonomic similarity between sites increases progressively with spatial scale, with significantly lower values and higher β-diversity at small spatial scales. The same pattern is evident for species similarity, using the Jaccard coefficient. Possible explanations for this pattern centre on: (1) the large-scale oceanic area examined (Indo-West Pacific), representing a metapopulation of echinoderms for the 2 other, smaller areas examined within (Pula Wé, Sumatra and Lakshadweeps); (2) greater biophysical instability and unpredictability at small spatial scales. Compared with larger spatial scales, these may be characterised by greater likelihood and influence of species migrations and extinctions on a site's total species composition. Hence, species composition may be highly changeable at small scales, leading to high β-diversity. These findings are based on 1 set of comparative data for 1 faunal group. Any wider conclusions drawn would be premature, although corals may also show greater β-diversity at small spatial scales. The extent to which patterns observed are evident for other marine species groups is not well known.KEY WORDS: Biodiversity · β-diversity · Taxonomic similarity · Echinoderms · Indo-West PacificResale or republication not permitted without written consent of the publisher

Fauna asociada a la nacra <i>Pinna nobilis</i> (Mollusca: Bivalvia) en la costa norte y este de Túnez

“…the greater taxonomic similarity of the lagoon and lagoon-sea mollusc and polychaete assemblages was probably more related to the selective environmental features of the brackish habitat (Gravina et al, 1988;Piraino and morri, 1990), which may conversely reduce the breadth of the taxonomic tree at the local scale. for the tunisian epizoic community on P. nobilis the taxonomic similarity generally decreased by increasing the spatial scale, apparently in contradiction to what izsák and Price (2001) stated for the echinodermata assemblage alone, although up to the province/ oceanic scale. the greater the species richness of a taxon for a particular habitat, the greater its sensitivity to changes in biological or environmental gradients.…”

“…in general the contingent of species found in Bizerta Lagoon accounted for fewer taxa in comparison with the regional richness as a consequence of the local habitat constraints ("lagoon" effect). moreover, the influence of the biogeographic lati-longitudinal gradient due to the colder near-Atlantic versus the warmer near-Levantine faunistic contingent can also increase the faunal variability and widen the taxonomic breadth (higher β-diversity; Price et al, 1999;izsák and Price, 2001). these aspects can lead to a higher β-diversity in terms of both numbers of registered taxa and increased taxonomic dissimilarity at the regional scale, as is best observed in the patterns of colonial sclerobiontic sponges and bryozoans.…”

Spatial patterns of soft-sediment benthic diversity in subtropical Hong Kong waters

“…The scales describing alpha and gamma diversity vary among authors, but gamma diversity usually refers to the overall number of species within a defined geographic area resulting from merging a number of alpha samples taken at a smaller spatial scale. Most marine surveys have been carried out on small spatial scales, and there are few specific studies of diversity at different spatial scales for the marine environment (for notable exceptions see Clarke & Lidgard 2000, Ellingsen 2001, Izsak & Price 2001, Ellingsen & Gray 2002.…”

The Benthic Megafaunal Assemblages of the CCZ (Eastern Pacific) and an Approach to their Management in the Face of Threatened Anthropogenic Impacts

“…These include average taxonomic distinctiveness (which is a measure of the mean taxonomic distance between species within a sample or study area), and variation in taxonomic distinctiveness which is a measure of the variance in taxonomic distance between species; both are relatively insensitive to sample size (Warwick and Clarke, 2001). In addition, complementing the idea of taxonomic distinctiveness, the concept of taxonomic similarity, the mean taxonomic distance between species from different samples or sites, has been introduced, allowing comparison across areas at different scales; this measure is likewise relatively insensitive to sampling intensity (Izsak and Price, 2001;Price, 2002;Price and Izsak, 2005). It is increasingly considered that such taxonomic diversity measures of biodiversity at both within-habitat and within-region scales, including across and between large ocean provinces, are invaluable for comparing and monitoring environments where full species lists are impracticable to attain Clarke, 1995, 2001;Gray, 1997;Price, 1999;Izsak and Price, 2001), and we propose their wider use for future assessing and monitoring in the CCZ.…”