Bioclimatic analyses for the distributions of Onthophagus nuchicornis, Onthophagus taurus, and Digitonthophagus gazella (Coleoptera: Scarabaeidae) in North America

Onthophagus nuchicornis (Linnaeus), Onthophagus taurus (Schreber), and Digitonthophagus gazella (Fabricius) (Coleoptera: Scarabaeidae: Scarabaeinae: Onthophagini) are species of dung beetles that have been used in relocation programmes to accelerate the degradation of cattle dung on pastures. Exotic in North America, all three species have expanded their distributions since their introduction onto the continent. Here we report development of CLIMEX (R) bioclimatic models using data collected before 2011 that predict the eventual North American distributions of these species. Data collected after 2010 is used to validate these models. Model outputs identify large regions of the central United States of America suitable for establishment of O. nuchicornis and O. taurus where these species have not been reported. These results indicate that the latter two species may already be present in these regions and undetected, that they have yet to expand into these regions, and (or) that factors restricting migration or dispersal prevent these species from occupying these areas. Model outputs for D. gazella suggest that the species has largely reached its predicted maximum distribution. These models can be used to aid the success of future relocation programmes elsewhere in the world and (or) to predict regions where these species are likely to spread without human intervention.