Are patterns of sampling effort and completeness of inventories congruent? A test using databases for five insect taxa in the Iberian Peninsula

Evaluating data quality and inventory completeness must be a preliminary step inany biodiversity research, particularly in the case of insects and high biodiversityareas. Yet, this step is often neglected or, at best, assessed only for one insectgroup, and the degree of congruence of sampling effort ffor different insect groupsremains unexplored. We assess the congruence in the spatial distribution of sampling effort for fiveinsect groups (butterflies, caddisflies, dung beetles, moths, and aquatic beetles) inthe Iberian Peninsula. We identify well-surveyed areas for each taxonomic groupand examine the degree to which the patterns of sampling effort can be explainedby a set of variables related to environmental conditions and accessibility. Irrespective of the general lack of reliable inventories, we found a general but lowcongruence in the completeness patterns of the different taxa. This suggests thatthere is not a common geographical pattern in survey effort and that idiosyncraticand contingent factors (mainly the proximity to the workplaces of entomologists)are differentially affecting each group. After many decades of taxonomic and faunistic work, distributional databases ofIberian insects are still in a very preliminary stage, thus limiting our capacity toobtain reliable answers to basic and applied questions. We recommend carrying out long-term, standardised and well-designed entomolog-ical surveys able to generate a reliable image of the distribution of different insect groups. This will allow us to estimate accurately insect trends and better under-stand the full extent of global biodiversity loss.This study has been supported by the projects BioWeb (MINECO:CGL2011-15622-E BOS), BANDENCO (JCMM: POII11-0277-5747)and IBERARTRO (SBPLY/17/180501/000492) founded by European Regional Development Fund (ERDF) through the Consejería de Educación, Ciencia y Cultura, Junta de Comunidades de Castilla-La Mancha. David Sánchez-Fernández is funded by a postdoctoral contract fromthe Spanish Ministry of Science and Innovation (Ramón y Cajal program; RYC2019-027446-IPeer reviewe