Calling the odds in the gamble of bioassessment: The importance of quantifying taxonomic sufficiency

Background/Question/Methods

Effective conservation management is dependent upon reliable information from bioassessment. Regulatory authorities typically use biological metrics based on course levels of taxonomic resolution (e.g. family). Although higher level taxa are often correlated with patterns at the genus/species level for both biodiversity assessment and ecological indicators of environmental conditions, the degree of correspondence is inconsistent and can represent an important risk of error for subsequent interpretation. Despite numerous taxa specific and region specific studies, the issue of higher taxa as a surrogate measure for species data is often overlooked in both the development of new methods and in the application of existing methods of biological assessment. This gulf between theory and practice can presents an obstacle to the uptake of novel methods for bioassessment and limits the clarity of information that is applied to strategies of conservation management. We used simulation models and real data from terrestrial and aquatic invertebrate communities to provide a systematic analysis of the effectiveness of higher taxa as a surrogate measurement for species data.

Results/Conclusions

In general, the correlation between respective taxonomic levels declines with increasingly coarse taxonomic resolutions as the basis for extrapolation becomes more distant. The skewed distribution of taxa within taxonomic hierarchies has a major effect on the correspondence between species data and higher level taxonomic classifications. The evenness of species assemblages is an important covariate with uncertainty in surrogate measures increasing as species assemblages become increasingly uneven. Skewed taxonomic hierarchies and variation in species evenness cause taxonomic accumulation curves to diverge at different rates for different levels of taxonomic resolution and emphasize the importance of sample size (effort) in taxonomic surrogacy. We introduce a new method that can be used to quantify taxonomic sufficiency and provide an estimate of the uncertainty represented by extrapolating higher taxon surrogate measures to measurements at the species level.