Abstract
Only a few mostly older studies analyzed the heterotrophic succession of dung beetles in the Midwestern United States. Such studies are needed to track the impacts of the climate crisis on heterotrophic succession and the associated decomposition processes that are central to soil fertility and carbon sequestration. The current study closes this knowledge gap and provides an easy and efficient method to estimate the relative attractiveness of individual dung pads during heterotrophic succession. The dung beetle community of Carpenter Farm in Adrian, Southeast Michigan was sampled for an entire year, including the winter months, using 15 pitfall traps baited with fresh cow manure. Samples were collected after 48 h and again after 72 h exposure time from the bucket content while leaving the bait unhampered. Eighty-four percent of all beetles were caught in the early sample, but only 6 species were missing in the later sample. A cluster analysis based on Pianka’s niche overlap identified a statistically higher mean overlap than expected by chance in a null model (model RA3) and divided the species community clearly into three clusters separating most relocators from most dwellers. Despite using a different method, my results confirmed the successional position of most previously described species and added data for several species with poor or unknown successional state. The successional segregation between dwellers and relocators discovered by the cluster analysis was paralleled by a significantly larger body size of relocators across taxonomic groups as compared to dwellers.
Highlights
A few mostly older studies analyzed the heterotrophic succession of dung beetles in the Midwestern United States
The dung beetle community of Carpenter Farm in Adrian, Southeast Michigan was sampled for an entire year, including the winter months, using 15 pitfall traps baited with fresh cow manure
I will focus on heterotrophic succession, in which a resource like a freshly deposited dung pad is gradually consumed and decomposed by a series of species occurring at consecutive times during its decomposition (Nakamura 1975)
Summary
Among the astonishing diversity of coprophilous organisms, coprophagous beetles stand out due to their abundance, trophic diversity, and variety of life cycles (Hanski and Cambefort 1991, Floate 2011). Almost all studies of the heterotrophic succession of dung so far collected dung pads (with the adjacent soil layer) after they were exposed for a certain amount of days Such methods collect cumulative samples, which do not necessarily represent the attractiveness of a dung pad for colonization after the passed exposure time but provide information on how long the resource stays attractive (or tolerable) for already inhabiting beetles. The third objective of this study was the collection of data from subtractive or exclusionary samples to deduce the relative attractiveness of dung after a 2-d versus 3-d exposure
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