Relative Contribution of Citizen Science, Museum Data and Publications in Delineating the Distribution of the Stag Beetle in Spain

SIMPLE SUMMARY: Conservation of insects requires a reliable knowledge of their distribution. Such knowledge is hard to obtain in many cases, due to lack of human power and funding for extensive surveys. Three ways out of this problem have been suggested: (1) data already available in museum collections, (2) data already available in the entomological literature and (3) use of citizen science projects as a cheap, efficient way to survey extensive territories. We assessed the contribution of each of these sources of information in delineating the Spanish distribution of the European stag beetle. Although citizen science quickly contributed more grid cells than the other sources, some grid cells were uniquely contributed by museum and publication data. Thus, the three sources of information need to be combined when targeting endangered species in a broad, heterogenous, sparsely populated territory such as Spain. ABSTRACT: Reliable distribution maps are in the basis of insect conservation, but detailed chorological information is lacking for many insects of conservation concern (the Wallacean shortfall). Museum collections, entomological publications and citizen science projects can contribute to solve this Wallacean shortfall. Their relative contribution to the knowledge on the distribution of threatened insects has been scarcely explored, but it is important given that each of these three sources of information has its own biases and costs. Here we explore the contribution of museum data, entomological publications and citizen science in delineating the distribution of the European stag beetle in Spain. Citizen science contributed the highest number of records and grid cells occupied, as well as the highest number of grid cells not contributed by any other information source (unique grid cells). Nevertheless, both museum data and publications contributed almost 25% of all unique grid cells. Furthermore, the relative contribution of each source of information differed in importance among Spanish provinces. Given the pros and cons of museum data, publications and citizen science, we advise their combined use in cases, such as the European stag beetle in Spain, in which a broad, heterogeneous, sparsely populated territory has to be prospected.