The determinants of host-associated microbiota: an experimental test in the Purple Pitcher Plant (Sarracenia purpurea)

Abstract

A long-term goal of ecologists is to understand forces that shape geographic variation in community composition, yet the relative roles of ecological selection and dispersal limitation remain poorly understood. I experimentally dispersed bacterial communities of the purple pitcher plant Sarracenia purpurea between four isolated New England peatland sites. I compared the bacterial communities of foreign inoculum treated pitchers to those of same-site control pitchers and inoculum-source control pitchers. I found that pitcher communities differed significantly between sites. Pitchers inoculated with bacterial communities from other sites remained more similar to same-site controls in nine out of 12 site-treatment combinations but became more similar to inoculum-source controls in the other three. These results suggest that strong site-specific ecological selection typically dominates dispersal limitation on a regional scale. However, dispersal limitation can occasionally override ecological selection, highlighting the spatial variability of microbial community assembly processes.