One of John’s dissertation projects examined the role of plant-microbe interactions in modulating fitness within versus beyond the range margin of Clarkia xantiana ssp. xantiana. He used a field transplant experiment, involving soil transplants as well, a greenhouse experiment, and microbiome characterization of roots and rhizosphere. His results suggest that there is mutualist limitation and pathogen escape beyond the range margin. This is among the first studies to examine these phenomena in the field.
Benning, J.W., & D.A. Moeller. 2021. Microbes, mutualism, and range margins: testing the fitness consequences of soil microbial communities across and beyond a native plant’s range. New Phytologist 229:2886-2900.