Arthropod morphospecies versus taxonomic species: a case study with Araneae, Coleoptera, and Lepidoptera

In times of biodiversity crisis there is an increasing need for faster and cheaper methods by which to achieve conservation goals. This situation is especially troublesome for invertebrates, and the use of morphospecies instead of taxonomic species has been proposed as a way around the taxonomic constraints in particular situations. We conducted a study in a modified native shrubland on New Zealand's South Island in which we sampled Lepidoptera, Coleoptera, and Araneae in autumn by beating and pitfall traps. All specimens were separated into morphospecies by a nonspecialist and identified by specialized taxonomists, and the results were compared. Results were analyzed with respect to correct separations (one taxonomic species to one morphospecies), lumping (more than one species classified as a single morphospecies), and splitting (one species separated into more than one morphospecies). Among the individual orders, Lepidoptera yielded the most accurate results (91% correct separation), whereas Coleoptera and Araneae yielded poor results (63% and 50%, respectively). The overall difference between the morphospecies and taxonomic species estimates for the site was only 3.3%, but this was an artifact caused by the splitting and lumping results balancing each other out. The accuracy of morphospecies separation varies greatly among different invertebrate groups, so the relationship between morphospecies and taxonomic species for a particular target group must be established beforehand. We recommend that some prior orientation should be given by expert taxonomists. When adopted with care, morphospecies present a useful tool for conservation, particularly for environmental impact assessment and when inventorying diversity does not require information on particular species.