Foliar Microbes as Drivers of Plant Performance and Trophic Dynamics

Sometimes referred to as the “great unseen,” microbes (e.g., bacteria, fungi, protists) are by far the most abundant organisms on Earth. Although soil microbial communities and their impacts on plant communities have received extensive attention, comparatively little is known about leaf microbes and their interactions with plants and higher trophic levels, particularly in forests. We began a long-term research effort at the Barro Colorado Nature Monument in 2010 to assess the diversity, distribution, and impacts of foliar microbiomes – specifically bacteria that occur upon and within leaves –on seedlings and saplings of co-occurring tree species. We demonstrated that experimentally altering foliar microbiomes with commercial antibiotics had pervasive effects on plant traits, plant-plant interactions, and interactions with higher trophic levels. Taken together, our results suggest that these cryptic organisms may drive important trophic cascades and ecosystem-level patterns, including plant diversity, nutrient cycling, and net primary productivity in forest biomes.