Degree-day models for development of the dung beetles Onthophagus nuchicornis, O. taurus, and Digitonthophagus gazella (Coleoptera: Scarabaeidae), and the likelihood of O. taurus establishment in southern Alberta, Canada

Abstract

Three studies were performed to assess the likelihood of establishing the dung beetle Onthophagus taurus (Schreber) (Coleoptera: Scarabaeidae) in southern Alberta, Canada. This European species was first reported in Florida in the 1970s and now occurs as far north as Michigan, United States of America. Its ability to establish in Canada is unknown, but is desired to accelerate the degradation of cattle dung on pastures. The first study examined egg-to-adult development at temperatures of 10–32 °C (in increments of 2 °C) to develop degree-day models for O. taurus and for two other closely related species of dung beetles. Onthophagus nuchicornis (Linnaeus), used as a positive control, is a European species common across Canada. Digitonthophagus gazella (Fabricius), used as a negative control, is an Afro-Asian species whose distribution is restricted in North America to the southern United States of America. The second study examined the overwintering ability of O. taurus and D. gazella in outdoor field cages. The third study compared climate parameters between southern Alberta and the northernmost recorded distribution of O. taurus. Results combined across the three studies show that O. taurus can complete egg-to-adult development and overwinter in southern Alberta. However, high overwintering mortality is predicted to prevent establishment of O. taurus in the region.

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

“…Distribution programs for D. gazella began in the 1960s (Bornemissza, 1970; Edwards, 2007), providing a 50‐year period of culturing the species. A short generation time combined with multiple generations per year (Tyndale‐Biscoe, 1990; Floate et al, 2015) could facilitate genetic changes between native and introduced populations. Molecular analyses seem warranted to assess the potential genetic differences between local ecotypes, regional, and intercontinental populations (the various climate strains referred to by Edwards, 2007).…”

“…Its establishment in Victoria, Australia at 36°S (Edwards, 2003) and parts of New Zealand (34–47°S; Forgie et al, 2018) demonstrate the ability of D. gazella to survive in more southerly latitudes. Floate et al (2015) report that D. gazella does not have an obligatory diapause and that the minimum temperature for egg development is 18 °C (with an average egg‐to‐adult development time of 52.2 days at 22 °C, a development threshold of 18 °C equates to 209 degree days). Tyndale‐Biscoe (1990) suggests that the species overwinters in Australia in both adult and larval stages.…”

“…Digitonthophagus gazella displays a broad tolerance to ecosystems and regions, particularly non‐forested cattle pastures in tropical, subtropical, and semi‐arid regions (Montes de Oca & Halffter, 1998). It also has a high dispersal rate (Seymour, 1980; Barbero & López‐Guerrero, 1992; Kohlmann, 1994; Álvarez et al, 2009; Noriega et al, 2011) and a relatively short generation time (Lee & Peng, 1981, 1982; Floate et al, 2015). Because of these attributes, D. gazella has become a dominant member of the dung beetle community in many locations (Doube et al, 1991; Lobo & Montes de Oca, 1997; Aidar et al, 2000; Marchiori et al, 2003; Koller et al, 2007; Matavelli & Louzada, 2008) and also dominates dung beetle literature, appearing in at least 1 120 scientific publications dedicated to its biology, ecology, and taxonomy (Génier & Davis, 2017).…”

Organic farming promotes biotic resistance to foodborne human pathogens

“…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., ). The dominance of O. nuchicornis could result from a number of possible mechanisms.…”

Effects of the veterinary anthelmintic moxidectin on dung beetle survival and ecosystem functioning

“…An additional explanation for the absence of emerging beetles in the second generation is the failure of beetles to develop within the timeframe of the experiment. While Palaearctic dung beetles are well-studied, detailed ecological and natural history information on the development of species in field conditions is scarce for most species (but see Landin 1961, Vessby 2001, Vessby and Wiktelius 2003, Floate et al 2014). Understanding the environmental factors that limit the development of dung beetles within semi-field experiments such as ours would be useful for future work.…”