PS 11-150 - Modeling the invasion ecology of microbial inoculants

Abstract: The use of potentially beneficial microorganisms in agriculture (microbial inoculants) has rapidly accelerated in recent years. To be effective as an agricultural tool, microbial inoculants must be able to survive and persist in novel environments while also not destabilizing the resident community or spilling over into adjacent natural ecosystems. Recent studies in both microbial and conservation ecology have identified propagule pressure and resident community resource niche structure as key determinants of the establishment success of introduced organisms. In agricultural applications of microbial inoculants, both the number of introductions (as application frequency) and the number of introduced individuals are known (inoculant concentration), making these introductions an ideal scenario for understanding the role propagule pressure plays in microbial invasion dynamics. Here, I adapt a macroecology propagule pressure model to a microbial scale using simulated data and present an experimental approach for testing the role of propagule pressure in microbial introductions. These simulations show that repeated applications of microbial inoculants can increase their establishment probability, but this pattern does not continue indefinitely. The point at which repeated applications stop increasing establishment probability is likely a function of the concentration of inoculant applied. Applying ecological modeling approaches to the microbial inoculants may aid in their sustainable use and reduce the risk of microbial invasion in agroecosystems.