Bioclimatic analyses for the distributions ofOnthophagus nuchicornis,Onthophagus taurus, andDigitonthophagus gazella(Coleoptera: Scarabaeidae) in North America

Abstract

Onthophagus nuchicornis(Linnaeus),Onthophagus taurus(Schreber), andDigitonthophagus 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®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 ofO. nuchicornisandO. tauruswhere 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 forD. gazellasuggest 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.

Organic farming promotes biotic resistance to foodborne human pathogens

“…(primarily A. pseudolividus ) (Data ). Floate, Watson, Weiss, and Olfert () report models predicting the distribution of O. taurus and O. nuchicornis along the west coast; our collections nearly mirror these geographic predictions. Despite dung beetles being diverse in samples across the west coast, we found that introduction of the exotic dung beetle O. nuchicornis appeared to be restructuring dung beetle communities (Floate et al., ); where O. nuchicornis was established from northern Washington State to central Oregon, this single species dominated dung beetle assemblages (north of approx.…”

“…Possible causes of this apparent influence of landscapes are unclear, but could result from cattle on grazeable land providing food that particularly benefited the introduced dung beetle O. nuchicornis (Floate & Kadiri, ). This species was unintentionally introduced to Northeastern North America from Eurasia, was first detected in western North America in 1945, and has since rapidly expanded its distribution across Canada and the Northern United States (Floate et al., ). Due to differences in cold‐hardiness and diapause requirements for O. nuchicornis , the current North American distributions of O. nuchicornis and O. taurus do not broadly overlap; however, in areas were the species do overlap, there is no evidence of competitive exclusion, and this is unlikely to change (Floate, Watson, Coghlin, & Olfert, ; Floate et al., ).…”

Global distribution patterns provide evidence of niche shift by the introduced African dung beetleDigitonthophagus gazella

“…(Vidaurre et al, 2008; Noriega et al, 2010). The northern latitudinal limit in North America corresponds to Missouri, USA (38°N; Floate et al, 2017). The southern latitude limit in South America is in Chillan, Chile (36°S).…”

“…Although some of these introductions could result from individuals hitchhiking rides within cattle dung during cattle transportation from one pasture to another. In the case of inland zones of Australia, Floate et al (2017) suggested that irrigation programs in dry regions could allow D. gazella to colonize and expand into these new areas that were previously not suitable for the species. However, some of the new localities outside its predicted range are almost entirely non‐irrigated (SOE, 2017), so that other unknown factors may have facilitated this expansion.…”

“…The author’s results showed a high degree of overlap between the two sets of parameters, suggesting that the climatic niche of the species is stable between native and invaded regions. Floate et al (2017) used bioclimatic models to predict the potential distribution of D. gazella and two other Onthophagini species in North America. Results for D. gazella indicated that it has likely already reached the North American limits of its potential distribution.…”