Weighing the costs and benefits of reduced sampling resolution in biomonitoring studies: Perspectives from the temperate rocky intertidal

Efficiency in biomonitoring studies is essential to maximize return (i.e. useful data) for investment (e.g. time, training, personnel). Here, we test several options for reducing data resolution when streamlining monitoring protocols, and use the results as a framework to discuss the costs and benefits of decreasing information when sampling intertidal assemblages. Specifically, we ask; (1) Is it necessary to collect species abundance data, or is species presence-absence information sufficient to differentiate sites? (2) Is it necessary to sample organismal abundance at the species-level or is coarser (higher taxon or functional group) resolution sufficient to resolve patterns of difference in intertidal community structure? and (3) How general are these patterns across different oceanic regions? We answer these questions using data from Northeast Atlantic, Northwest Atlantic, Northeast Pacific, and Southwest Pacific intertidal monitoring studies. Results show that compared to species-level sampling, genus-level sampling requires knowledge of 25% fewer taxa, but results in only a 5% difference in the ability to discern between-sample similarities. Likewise, family-level sampling involves 50% fewer taxa, and is accompanied by only an 8% difference in between-sample similarities. Species lists and functional groups were variable in performance, working well for some regions, and poorly for others. These findings will assist in the selection of monitoring protocols with the potential for increased geographic scope and temporal frequency of sampling, resulting in longer time series of data collection, and a reduction in the required taxonomic skills for individuals involved in scientifically useful biomonitoring programs.     

A new method based on taxonomic sufficiency to simplify studies on Neotropical ant assemblages

Insects, particularly ants, are good bioindicators of the state of ecosystems. Nevertheless, incorporating them into conservation surveys is expensive due to problems associated with their identification, which is exacerbated by the fact that there are fewer and fewer taxonomists working today. “Taxonomic sufficiency” (TS), which identifies organisms to a level of taxonomic resolution sufficient enough to satisfy the objectives of a study, has never been applied to Neotropical ant communities. We analysed five Neotropical datasets representing ant assemblages collected with different sampling methods in various habitats. We first treated them using two complementary and cumulative TS methods, higher-taxon and “indicator taxa” surrogacies, before testing a new approach called “mixed-level method” that combines the two previous approaches. For the higher-taxon surrogacy, we showed that, above species, genus is the most informative taxonomic level. Then, mixed-level method provided more information on ant assemblages than did the two others, even though the “indicator taxa” surrogacy was based on relevant indicator genera. Although habitat type has no effect on its efficiency, this new method is influenced by the dataset structure and the type of sampling method used to collect data. We have thus developed a new method for analyzing Neotropical ant faunas that enables the taxonomic work linked to the identification of problematic species to be significantly reduced, while conserving most of the information on the ant assemblage. This method should enhance the work of Neotropical entomologists not specialised in taxonomy, particularly those concerned with biological conservation and indication.