The arms race between predator and prey has been played out endless times in evolutionary history, and so adaptations for predator defense are ubiquitous in animals. Defense against microorganisms is at least as important as defense against predatory macro-organisms, for the threat imposed can be much more insidious. Microbes up to a trillion per gram of soil compete intensively for the energy in the chemical secretions, excretions and bodily structures of macro-organisms, and so it is surprising that little if anything is know about whether microbes feed on those chemical signals that organisms release into the environment to coordinate or influence important activities ranging from predator defense to reproduction. Until now, evaporation and diffusion were thought to be the eventual fates of chemical signals, not microbial consumption. If microbes have this impact, the signaling organisms must compensate production to offset the anticipated loss to microbes, and so the costs of producing a chemical signal will always be higher than predicted based on loss due to evaporation and diffusion. Models that attempt to correlate chemical design with behavior will have to be revised if microbes routinely degrade the chemical signals of higher organisms.
The red-backed salamander, Plethodon cinereus, is the most common terrestrial vertebrate in the northeastern United States, but it also is fast becoming a model species for chemical signal production spanning predator defense, territorial defense, and courtship behavior. P. cinereus can chemically label and avoid the scent trails of garter snake predators that feed on salamanders. P. cinereus also scent marks and defends feeding territories, and the males produce scent to attract mates. All these chemical signals are energy-containing molecules that microbes can potentially utilize, and so microbes could have a considerable energetic impact on salamanders attempting to survive predation, defend resources, or influence reproduction through the production of chemical signals.
The investigators will use ultraviolet sterilization and microfiltration techniques in both the laboratory and field to test whether the presence or relative absence of microbial communities have consequences for the duration of the chemical signal produced by P. cinereus to label and avoid garter snake predators. Microbial impacts on territorial and courtship chemosignals may also be examined if time permits. The demonstration of microbial impacts on chemical signals will be immediately relevant to many issues relating to signal production and duration in chemical ecology, and especially to a better understanding of the diverse ways microorganisms may impact broad categories of behavior among higher organisms.
This research will be undertaken with a strong emphasis on mentoring and interdisciplinary problem solving that have resulted in high levels of productivity and numerous awards among undergraduates and graduates working on the research team. This process has resulted in student-driven linkages with industry and the medical community that have made the research not only more informative but more broadly relevant to societal needs. One outcome of this mentoring and interdisciplinary thinking is the idea developed for study in this proposal.
