Antibiotics were discovered from soil microbes >100 years ago. Since then, the ecology of antibiotics remains virtually unexplored. While antibiotic production is often considered to be a mechanism for microbial warfare, the intended target of these compounds is still unresolved. Dan Janzen was one of the first to propose that antibiotics may be produced as a deterrent against animals. My preliminary work in both the field and mesocosms shows that antibiotics decrease the numbers of some,but not all soil invertebrates, and that at least one taxa senses and actively avoids antibacterials in the litter. Here we test two hypotheses for such behavior: 1) that invertebrates are avoiding patches of low food supply, and 2) that invertebrates with an abundant gut flora are protecting their microbiome. These hypotheses explore a novel, and likely pervasive, set of interactions between bacteria, fungi, and animals.
Results/Conclusions
At Barro Colorado Island in Panama and Yasuni Research Site in Ecuador, we found that antibiotic compounds decrease rates of decomposition through the depression of key fungal and bacterial decomposers. In both field and mesocosm studies, we found that antibiotics decrease abundance and diversity of soil invertebrates. Furthermore, we found that the deleterious effect of antibiotics may ecnourage soil invertebrates to develop an ability to sense and avoid antibiotic compounds. Our study suggest that antibiotic compounds can have widespread impacts on communities and play a role in creating the patchy nature of forest floor communities. At a time of growing antibiotic resistance and dwindling supplies of new antibiotics, understanding the target and action of antibiotics is key to understanding their production and diversity. Moreover, the production of poisons by microbes likely ramifies upward to shape an ecosystem’s rates of decomposition and nutrient cycling.