Taxonomic distinctness and diversity measures: responses in marine fish communities

In a recent paper Warwick & Clarke (1995: Mar Ecol Prog Ser 129:301-305) introduced 2 new measures of community diversity, Delta and Delta*. These measures differ from more conventional diversity indices by incorporating the taxonomic relatedness of species into their calculation. In this paper we compare temporal trends in Delta and Delta* with more conventional diversity measures for the demersal fish community of the northern North Sea. We show that, contrary to the findings for benthic invertebrates, indices that incorporate taxonomic distinctness show identical time trends to conventional measures. This, perhaps, suggests that when perturbations are sufficiently large to affect conventional indices of diversity, taxonomic diversity indices may already have reached levels from which they march in step with conventional indices.