Disentangling the effect of climate and human influence on distribution patterns of the darkling beetle Scotobius pilularius Germar, 1823 (Coleoptera: Tenebrionidae)

Scotobius pilularius Germar 1823 (Tenebrioninae: Scotobiini) is mainly distributed in natural temperate and mesic grasslands of the Pampean biogeographic province. However, it is also found in climatically extreme environments such as cold and dry grasslands within the Patagonian biogeographic province. In these extreme environments, S. pilularius is found outside of natural habitats, in areas associated with human settlements. In the present paper, the role of climatic conditions and human settlements as determinants of the observed spatial distribution of S. pilularius in its natural distribution and outside that area is assessed. Three following hypotheses are tested: species occurrence is determined by i) climate; or ii) human settlements; or iii) both climate and human settlements. The results suggest that, while the climate and human settlements hypothesis is consistent with the data acquired within the S. pilularius natural distribution area, only the human influence hypothesis significantly explains its distribution outside of its natural area. This outcome suggests that S. pilularius moved from living in a complete disassociation to human settlements or asynanthropy before human settlements in its natural area, to living in close association with human settlements or synanthropy outside of its natural area.