Dung beetles of an Australian tropical savanna: Species composition, food preferences and responses to experimental fire regimes

Abstract

Dung beetles are an ecologically important group of insects globally, but the ecology of the Australian fauna is poorly known. Here, we report on the first ecological study of dung beetles in an Australian tropical savanna, documenting species composition, food preferences and responses to fire. Dung beetles were baited using dung from five types of vertebrates as well as mushrooms. We sampled at nine plots subject to experimental fire regimes (three replicates each of high fire severity, moderate fire severity and unburnt over 15 years) at the Territory Wildlife Park near Darwin. Our samples were comprised entirely of nine native species of Onthophagus. Dog dung was the most attractive bait, recording all nine species and nearly 80% of all individuals, whereas no beetles were recorded at either wallaby or magpie-goose dung. Dung beetle abundance was highest under high fire severity and was negatively correlated with the cover of woody vegetation, a result driven by the two most common species, O. minsiculus and O. nr. quadripunctulatus. Our results indicate that Onthophagus is the dominant genus in dung-beetle assemblages of monsoonal Australia, as it is in open habitats of the Australian wet tropics. All our species of Onthophagus are relatively small (≤10 mm body length) and are 'tunnellers', storing dung and other food resources in tunnels dug immediately below the food source. Such an overwhelming dominance by small tunnellers does not occur in African savannas, reflecting the far lower availability of large mammalian dung in Australia.

Quantifying the post‐fire recovery of taxonomic and functional diversity of dung beetles in the Brazilian Pantanal

“…This study provides evidence that despite the distinct species community, taxonomic and functional diversity of dung beetles did not change post-fire, highlighting the resilience of dung beetles to fire in the open ecosystems (Carvalho et al, 2020;Nunes et al, 2019;Palusci et al, 2021). In this sense, there is a possibility that the two assemblages are not separated because of the high dispersal ability of dung beetles.…”

“…The species richness, number of individuals, biomass and diversity of dung beetles did not differ between unburned and burned sites. Indeed, different from tropical forests where dung beetles have demonstrated to be sensitive to fire effects (de Andrade et al, 2011, 2014), in open ecosystems such as rangelands in North America (Smith et al, 2019), savannas in South America (Amazon – Louzada et al, 2010 and Cerrado – Nunes et al, 2019) and Australia (Carvalho et al, 2020) and grasslands in Italy (Palusci et al, 2021), a strong resilience of dung beetle communities to this disturbance has been observed. Nunes et al (2019) compared the same community before and after fire and suggested that three non‐mutually exclusive mechanisms promoting the resistance and recovery of dung beetles in open ecosystems could be acting in synergy: (i) dung beetles are present in the rainy season, whereas fires occur during the dry season; (ii) dung beetles remain buried during diapause in the dry season, protecting individuals from being burned during fire events; and (iii) replacement of species in burned areas by the movement of individuals from unburned areas.…”

“…The functional traits composition was similar between unburned and burned sites, demonstrating that taxonomic composition is more sensitive than functional structure to fire effects in the Brazilian Pantanal. Indeed, functional responses of dung beetles depend mainly on the intensity of the disturbance (see Beiroz et al, 2018), where dung beetle communities are highly resilient to disturbances caused by fire in open ecosystems (Carvalho et al, 2020; Nunes et al, 2019; Palusci et al, 2021). Since a low intensity disturbance in highly diversified communities does not modify functional structure (Magnago et al, 2014), but may alter species composition, the effects of a short‐term post‐fire (1 year) may represent a low disturbance for dung beetle functional traits in Brazilian Pantanal.…”

“…The species richness, number of individuals, biomass and diversity of dung beetles did not differ between unburned and burned sites. Indeed, different from tropical forests where dung beetles have demonstrated to be sensitive to fire effects ( de Andrade et al, 2011de Andrade et al, , 2014, in open ecosystems such as rangelands in North America (Smith et al, 2019), savannas in South America (Amazon -Louzada et al, 2010 andCerrado -Nunes et al, 2019) and Australia (Carvalho et al, 2020) and grasslands in Italy (Palusci et al, 2021), a strong resilience of dung beetle communities to this disturbance has been observed. Nunes et al (2019) Furthermore, we added one factor that also may help to explain the lack of differences in dung beetle communities between unburned and burned sites in the Brazilian Pantanal:…”

Fire ash residues do not affect ecological functions of Phanaeus palaeno in Cerrado grassland

“…Dung beetles are sensitive and respond strongly to changes in vegetation structure, soil, and habitat microclimate (Escobar et al, 2007; Louzada et al, 2010). Some studies have shown that fire affects the tropical forest dung beetle community (de Andrade et al, 2014; França et al, 2020) and the abundance of dung beetles in Mediterranean mountain environments (Palusci et al, 2021), but not the abundance of dung beetles living in open environments, such as the Cerrado (Nunes et al, 2019; Carvalho et al, 2020; Gonçalves et al, 2022). Up to date, no studies have addressed whether post‐fire factors influence the ecology of dung beetles.…”