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Ephemeral resources are excellent environments in which to study the dynamics of resource partitioning within insect communities. Among the many groups of organisms that exploit decomposing substrates, such as dung and carrion, is the beetle family Scarabaeidae. Scarab beetles are readily collected and identified in southeast Ohio mixed-hardwood forest, where a portion of this research was conducted. Among this diverse group are multiple guilds, which partition temporary resources in time and space. This study investigated how selected scarab species partition resources in time, and to determine the volatile chemical profile of these resources throughout decomposition.Three sites were established in Vinton County, Ohio on dry ridge tops. Resources preferences and exploitation of dung, carrion, and fungi were examined via baited pitfall trapping at two time periods, 0-24 hours and 2-7 days. Analysis of variance revealed dung as the most attractive resource in 0-24 hour stage, and carrion to be the most attractive from 2 to 7 days. Ateuchus histeroides was the most abundant species in the 24-hour samples, specifically in the dung treatment. Results suggested that A. histeroides was a more specialized species, having the ability to detect and exploit resources early in succession. Overall, saprophytic scarabs in southeast appear to be opportunistic in their attraction to these resources.The response of two species, Ateuchus histeroides and Geotrupes splendidus, to decomposing dung, carrion, and fungi was tested in a controlled environment. Beetles were allotted 10 minutes to respond to a single resource in a wind-tunnel. Each resource was tested at 24-hour intervals of decay from 0 to 168 hours in a randomized complete block design. Ordinal logistic regression showed that A. histeroides responded significantly to fresh dung, and G. splendidus responded to all resources with little discrimination among decay stages. These results suggest that A. histeroides assumes a more specialized feeding strategy, whereas the strategy of G. splendidus is more general and opportunistic.The volatile chemical profiles of decaying dung, carrion, and fungi were determined by gas chromatography-mass spectrometry. Results indicated multiple compounds among each resource, with ten of those compounds shared between resources. There also were compounds specific to fresh dung, not present in proceeding decay stages. These results could suggest potential attractive compounds to which A. histeroides and G. splendidus are responding, and generate hypotheses for determining the appropriate chemical blend that would elicit a natural response. |
