Microbial volatiles and succession of beetles on small carrion

Abstract

Ecological succession is understood in general terms (facilitation, tolerance, inhibition) even though the system‐specific mechanisms often remain elusive. The succession of insects on carrion is an important model because of its applications to ecosystem function and forensic science. It recently has been hypothesized that changing volatile cues produced by microbes drive succession on carrion. The authors investigated how two blends of sulphur volatiles attracted beetles that typically colonise during the fresh or active decay stages of carrion decomposition. Most beetles attracted to a fresh carcass or to a fresh carcass + dimethyl sulphide/methyl thiocyanate (DMS/MeSCN) blend were burying beetles that breed on small carcasses (95% Nicrophorus spp. other than Ni. pustulatus), with more beetles attracted to the chemically‐supplemented traps. Beetles attracted to carcasses in active decay (Ni. pustulatus, silphines, staphylinids) were also attracted to a fresh carcass + dimethyl disulphide/dimethyl trisulphide (DMDS/DMTS) blend, evidence that DMDS and DMTS are important cues for beetles during the middle stages of decomposition. The Fresh + DMDS/DMTS traps, however, were not a perfect mimic of a carcass in active decay. There were seasonal differences in attractiveness that the authors speculate are due to beetles responding to cues from carcasses used for feeding versus breeding. A second experiment demonstrated a synergy between DMDS and DMTS in attracting Ni. pustulatus and Euspilotus assimilis. The results support the hypotheses that changes in microbial communities and their volatiles during decomposition drive the succession of carrion‐frequenting insects and that blends of volatiles are necessary for some species to identify the targeted stage of decomposition.

Preference for and resistance to a toxic sulfur volatile opens up a unique niche inDrosophila busckii

“…This discovery is intriguing, as multiple studies have demonstrated the use and prevalence of DMTS over DMDS for navigation and oviposition in other species, such as carrion-eating flies like Lucilia sericata and Calliphora vicina . Furthermore, electroantennogram studies indicated strong responses to DMTS but limited to no response to DMDS 51,52 . Given that there are no reports of Dbus being captured from carrion or carrion-mimicking flowers, it is reasonable to hypothesize that this shift in ligand preference between these two structurally related oligosulfides could be a contributing factor in the discrimination of food and oviposition sites.…”

“…The use of short-chain oligosulfides as semiochemicals by insects has been documented in other contexts, involving mosquitoes, bed bugs, blow flies, parasitic wasps, cabbage root flies, and carrion-mimicking flower breeding flies [46][47][48][49][50] . Decaying carrion and carrion-mimicking flowers have been found to emit significant amounts of both DMDS and DMTS in their bouquets 47,50,51 .…”

The effect of pioneer carrion beetles on the emission of volatile organic compounds and carrion insect community assembly

“…Recently, methyl thiocyanate has been identified as an important attractant (Trumbo & Steiger, 2020 ). Moreover, the synergy, emission rates (volatility), and relative concentrations of multiple compounds are important as well (Podskalská et al., 2009 ; Trumbo & Dicapua, 2021 ; Trumbo & Newton, 2022 ). Therefore, to elucidate the comprehensive mechanisms that attract carrion insects to carcasses, dose–response tests and experiments considering relative concentrations of various volatile organic compounds are also needed.…”

“…However, recent studies have elucidated the mechanisms of carrion insect succession from a microscopic perspective. These studies have demonstrated temporal changes in carrion insects corresponding to changes in volatile organic compounds emitted from carcasses (Recinos‐Aguilar et al., 2020 ; Trumbo & Newton, 2022 ). This idea is called the gas‐emanation hypothesis (Nadeau et al., 2015 ), and carrion insect succession is thought to be driven by the temporal change in volatile organic compounds perceived by different insects (Dekeirsschieter et al., 2009 , 2012 ; Forbes et al., 2014 ; Kasper et al., 2012 ; Stadler et al., 2013 ) resulting from microbial succession on carcasses (Pechal, Crippen, et al., 2014 ).…”