Succession of dung-inhabiting insects follows succession of dung-emitted volatiles
The ability to locate food is of utmost importance for animals. Insect decomposers locate their resources using volatile organic compounds, even to the extent that they can be deceived by plants that mimic the scent of their natural food resources (such as dung). Physical properties of natural resources for insect decomposers tend to change drastically during their decomposition (e.g. decreasing dung moisture) which is often accompanied by changes in their chemical composition and profile of volatile compounds emitted. As such, they could provide valuable clues for insect decomposers who display a succession in their resources, with individual species usually associated with a particular resource age. We have therefore investigated a potential link between successional patterns of dung-inhabiting insects (particularly beetles and dipterans) and the succession of dung emitted volatiles.
Fig.: Aphodius rufipes
Dung-inhabiting dipterans were predominately associated with the early successional group of volatiles (consisting primarily of volatiles produced by anaerobic microbes defecated by dung producer), mainly with 1-butanol. Beetles were associated predominantly with the late successional group (consisting primarily of volatiles produced by aerobic soil microbes), mainly with dimethyl trisulfide.
Our results suggest that there is indeed a connection between successions of dung-inhabiting insects and dung emitted volatiles. This connection is, however, based on preferences of larger insect groups (beetles and dipterans), rather than individual species within those groups, for larger batches of dung emitted volatiles (produced by either anaerobic or aerobic microbiota). In both insect groups, preference for certain batches of volatiles is highly probable to carry the information of dung physical properties. For dipterans, early successional volatiles could signal that the dung is fresh, without a firm crust and without a host of predatory beetles ready to prey on them. For beetles, the late successional compounds could signal a lesser amount of dung moisture, which could be lethal to them, as well as a presence of fly larvae to prey on.
Finally, our study presents another piece of evidence supporting the hypothesis that the succession of dung-inhabiting insects is driven by habitat filtering, with dung emitted volatiles used as a signal for other dung conditions (dung moisture, etc.).
Sládeček F., Dötterl S., Schäffler I., Segar S. T., Konvička M. (2021) Succession of dung-inhabiting beetles and flies reflects the succession of dung-emitted volatile compounds. Journal of Chemical Ecology 47: 433-443. DOI: 10.1007/s10886-021-01266-x