Influence of taxonomic resolution, biological attributes and data transformations on multivariate comparisons of rocky macrofaunal assemblages

Abstract

Multivariate comparisons of impacted and non-impacted biotic assemblages require decisions to be made about the taxonomic resolution to be used, biological attributes to be measured and whether the contributions of common, or combinations of common, intermediate and rare taxa should be emphasised. This study shows how these decisions affect comparisons of exploited and non-exploited rocky infratidal macrofaunal assemblages distributed across a biogeographic transition zone on the south-east coast of South Africa. Two-way crossed ANOSIM tests were used to test for differences in the structure of assemblages among regions of the coast and between exploited and non-exploited localities. In tests based on presence/absences, significant differences in assemblages among regions and between treatments were evident only at the species level. In tests based on densities and biomasses, regional differences were evident at the species, order, class and phylum level, and were irrespective of whether dominant or combinations of dominant, intermediate and rare taxa were emphasised. Significant differences in exploited and non-exploited assemblages were evident in all of the comparisons except those in which numerically dominant higher taxa were emphasised. These results do not suggest that the natural environmental gradient influences the fauna more by species replacements than by changes to the proportions of higher taxa, nor do they indicate that natural environmental variations and anthropogenic disturbances modify macrofaunal assemblages at different taxonomic levels. Further studies are needed to establish whether the taxonomic level, at which modification of assemblages occurs, varies with the type of disturbance (e.g. pollution vs exploitation, strong vs weak gradients) or biotic component (e.g. rocky vs soft-bottom assemblages) under consideration.

Biodiversity of benthic assemblages on the Arctic continental shelf: historical data from Canada

“…This was especially true with tests based on densities. ANOSIM is sensitive to the level of taxonomic resolution: values of the R-statistic generally decrease as the level of taxonomic resolution increases (Somerfield & Clarke 1995, Lasiak 2003. For the V and F regions, most of the significant differences with other regions occurred up to the Phyla level.…”

Taxonomic resolution needed to describe invertebrate assemblages and to detect harvesting effects on coral reef ecosystems

“…To date, only one study specifically investigated the performance of the TS approach on other types of disturbance (e.g. invertebrate exploitation), comparing rocky-shore communities in exploited and protected areas at different taxonomic resolutions (Lasiak 2003). Lasiak (2003) found that even though the data matrices at different taxonomic resolutions were strongly correlated, clear, significant differences between exploited and non-exploited assemblages only occurred at species level.…”

“…invertebrate exploitation), comparing rocky-shore communities in exploited and protected areas at different taxonomic resolutions (Lasiak 2003). Lasiak (2003) found that even though the data matrices at different taxonomic resolutions were strongly correlated, clear, significant differences between exploited and non-exploited assemblages only occurred at species level. In the latter case, anthropogenic exploitation changed the assemblages in a different way as it was essentially targeting a single group, the molluscs (Bigalke 1973, Lasiak 1992, therefore, resulting in differences in abundance rather than in species composition (Lasiak 1998).…”

Influence of taxonomic resolution on multivariate analyses of arthropod and macroalgal reef assemblages

“…order or phylum) are sufficient for the detection of impacts on the marine environment (Warwick 1988a,b). Moreover, even broad-scale regional patterns can be detected using phylum-level identifications (Lasiak 2003) or at the very least, data aggregated to the family level (Hewlett 2000). These findings have important implications for the design of future sampling programs because they suggest that, by adopting a coarser taxonomic level identification, similar outcomes may be achieved with reduced sample processing costs.…”

“…The degree to which anthropogenic impacts can be detected using coarser taxonomic resolution has been widely documented among soft bottom (Ferrero & Cole 1995, Somerfield & Clarke 1995, Vanderklift et al 1996, Olsgard et al 1997, Stark et al 2003) and other benthic marine environments (Smith & Simpson 1993, Lasiak 2003, Anderson et al 2005a. Fewer studies have examined the extent to which taxonomic resolution influences the detection of natural patterns and gradients in community structure among unimpacted benthic environments, despite the potential time and cost savings that may be accrued.…”