Linking bacteria, volatiles and insects on carrion: the role of temporal and spatial factors regulating inter-kingdom communication via volatiles

Abstract

Multi-kingdom community complexity and the chemically mediated dynamics between bacteria and insects have recently received increased attention in carrion research. However, the strength of these inter-kingdom interactions and the factors that regulate them are poorly studied. We used 75 piglet cadavers across three forest regions to survey the relationship between three actors (epinecrotic bacteria, volatile organic compounds (VOCs) and flies) during the first 4 days of decomposition and the factors that regulate this interdependence. The results showed a dynamic bacterial change during decomposition (temperature–time index) and across the forest management gradient, but not between regions. Similarly, VOC emission was dynamic across a temperature–time index and the forest management gradient but did not differ between regions. However, fly occurrence was dynamic across both space and time. The strong interdependence between the three actors was mainly regulated by the temperature–time index and the study regions, thereby revealing regulation at temporal and spatial scales. Additionally, the actor interdependence was stable across a gradient of forest management intensity. By combining different actors of decomposition, we have expanded our knowledge of the holistic mechanisms regulating carrion community dynamics and inter-kingdom interactions, an important precondition for better describing food web dynamics and entire ecosystem functions.

Evisceration residues from hunted roe deer as a resource for necrophagous insect fauna in the Black Forest, Germany: a preliminary study

“…At every site, we placed northward facing metal cages (62 × 93 × 69 cm, mesh 4 × 12 cm) with two pitfall‐traps (9 cm diameter openings), at the northwest and southeast corner of the cages to trap Diptera and Coleoptera (Weithmann et al 2020, 2022, von Hoermann et al 2021). At carcass and residue sites, we placed the roe deer samples in the cages, to prevent vertebrate scavengers from dragging them away.…”

“…We used distilled water with odourless detergent as trapping liquid. While pitfall‐traps are mostly used to sample non‐flying insects, for carrion studies pitfall‐traps are also successfully applied to sample flying taxa like Diptera or flying Coleoptera (Weithmann et al 2020, 2022, von Hoermann et al 2021). We collected insect samples from the pitfall‐traps in two‐day (48 h) intervals for a total of 18 sampling intervals (I01–I18).…”

Bridging the gap between decomposition theory and forensic research on postmortem interval

“…For example, the primacy of microbes in decomposition has long been appreciated [ 32 , 33 ], but their central role in shaping waves of decomposer colonisation of remains, and aspects of their behaviour, is becoming ever clearer [ 34 – 36 ]. Identification of such interdependencies allows for new investigations into the role of decomposer interactions [ 11 ].…”

“…These drivers may be environmental, physicochemical, biological, or ecological, and their complex interdependencies mean a multidisciplinary approach is critical. For example, gases and volatile organic compounds (VOCs) emitted as the result of initial and subsequently changing microbial activity are shaped by the deceased individual’s background and environmental context, and this in turn will strongly affect the colonisation patterns of insects or olfaction-dependent vertebrate scavengers [ 11 ]. Exploration of such relationships might require expertise from pathologists, chemists, microbiologists, entomologists, and ecologists.…”

“…However, current models for estimating PMI, or other approaches to measuring time-since-death, lack generality or ignore many of the complexities of decomposition [ 5 , 8 – 10 ]. For example, taphonomic approaches may ignore insect activity, while insect-based approaches may ignore the importance of microbes or the role of larger vertebrate scavengers [ 11 , 12 ]. Other intrinsic attributes of a deceased individual, such as body mass or pharmaceutical history, may further complicate matters.…”