Using range size to augment regional priority listing of charismatic insects

Abstract

Extinction risk assessments are challenged by population data deficiencies, especially at large scales and for diverse taxa like insects. We generally have a better handle on insect distributions than on their population sizes and trends. As a composite expression of other traits and population factors, geographic range size may compensate for lagging population data and extend regional status coverage to more insect species over more jurisdictional area, at least within the relatively accessible and charismatic taxa. We tested this using a range-based index of regional extinction risk and two “incomplete” regional status assessments for North American dragonflies and damselflies (Odonata). The range index revealed signatures for generalizing High-concern and Low-concern status throughout the regional jurisdictions and Odonata species pools. Using the High-concern signature, we identified 38 regional priority candidates that currently lack regional concern status in the Midwest United States, and 15 candidates in central Canada where regional status was never assessed. Our robust range index covered almost 10 % of the world's described Odonata species and could be adapted to other regional jurisdictions and insect groups supported by strong community science. Range size alone may offer a workable approach for estimating regional extinction risk and facilitating prioritization of charismatic insects in regions lacking population trend data and IUCN Red Lists.