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

Abstract

There are currently few recommendations regarding the taxonomic resolution required to sufficiently describe patterns of community structure among temperate rocky-reef invertebrate and macroalgal assemblages. Studies conducted in a range of other aquatic systems have indicated that there is a high degree of redundant information conveyed at the species level, in comparison to higher taxonomic levels. This has important implications for the design of many ecological studies in terms of the allocation of resources. This study examined the impact of taxonomic aggregation on the detection of multivariate patterns in faunal and macroalgal assemblage structure amongst temperate subtidal reef communities in southern Australia. I considered the level at which taxonomic aggregation led to the loss of resolution in multivariate patterns, impairing conclusions regarding assemblage patterns at the species level. This study found that the impact of taxonomic aggregation varied for faunal and macroalgal assemblages. While family-level identifications were sufficient to discriminate faunal assemblages to a degree comparable to species-level identifications, aggregation of macroalgal data to higher taxonomic levels was substantially less informative. Thus, whereas significant cost-savings can be achieved by identifying invertebrate taxa to family with little or no loss of information, the same is not true for macroalgal assemblages. Differences between faunal and algal assemblages were attributable in part to the distribution of species within higher taxa. In particular, the aggregation of macroalgal species belonging to the order Fucales (e.g. Sargassum, Cystophora etc.) resulted in impaired representation of assemblages in multivariate patterns, as a consequence of the diversity, dominance and wide distribution of this order within benthic macroalgal groups of southern Australia.