Diet shifts by adult flightless dung beetles Circellium bacchus, revealed using DNA metabarcoding, reflect complex life histories
Life history changes may change resource use. Such shifts are not well understood in the dung beetles, despite recognised differences in larval and adult feeding ability. We use the flightless dung beetle Circellium bacchus to explore such shifts, identifying dung sources of adults using DNA metabarcoding, and comparing these with published accounts of larval dung sources. C. bacchus is traditionally considered to specialise on the dung of large herbivores for both larval and adult feeding. We successfully extracted mammal DNA from 151 adult C. bacchus fecal samples, representing 16 mammal species (ranging from elephants to small rodents), many of which are hitherto undescribed in the diet. Adult C. bacchus showed clear dung source preferences, especially for large herbivores inhabiting dense-cover vegetation. Our approach also confirmed the presence of cryptic taxa in the study area, and we propose that this may be used for biodiversity survey and monitoring purposes. Murid rodent feces were the most commonly fed-upon dung source (77.5%) for adult C. bacchus, differing markedly from the large and megaherbivore dung sources used for larval rearing. These findings support the hypothesis of life history-specific shifts in resource use in dung beetles, and reveal a hitherto unsuspected, but ecologically important, role of these dung beetles in consuming rodent feces. The differences in feeding abilities of the larval and adult life history stages have profound consequences for their resource use and foraging strategies, and hence the ecological role of dung beetles. This principle and its ecological consequences should be explored in other scarabaeids.
KeywordsBiodiversity survey Circellium bacchus Coprophagy Environmental DNA Next generation sequencing Megaherbivores Mitochondrial DNA Scarabaeinae Rodent feces
We thank South African National Parks for permission to work in the Addo Elephant National Park, where the dung beetle fecal sampling was conducted under Permit KERGIH1114. Three reviewers provided useful comments that improved the manuscript.
Author contribution statement
GIHK, ML, PT, and EC conceived and designed the study, collected and analyzed the data, and wrote the manuscript; GFF, FB, AB, and DR extracted and amplified DNA and contributed to the writing of the paper.
This study was funded through the Protea South Africa—France Science and Technology Co-operation (NRF (South Africa) Grant no. 85062 and Ministère des Affaires Étrangères Grant no. 2973PM), with additional support by the Nelson Mandela University, Centre National de la Recherche Scientifique, and University Grenoble Alpes. ML was supported by an NRF (South Africa)—Department of Science and Technology Innovation Postdoctoral Fellowship.
Compliance with ethical standards
Conflict of interest
We declare that we have no competing interests.
Data are available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.rm2n41j.
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