Tropical Endophyte Assembly and Function.
Foliar endophytic fungi are environmentally-acquired symbionts, whose diverse communities reside cryptically within the healthy photosynthetic tissue of all plant species sampled to date. Endophyte colonization can benefit host plants by enhancing defense against pathogens and herbivores, but with demonstrated costs including latent pathogenicity and lowered host photosynthetic rate. A critical question in both endophyte ecology and broader ecological theory is to what extent do abiotic and biotic factors affect community composition? Moreover, does community assembly of endophytes carry functional consequences for plant hosts?
I am looking at these questions using Theobroma cacao (the cacao tree from which we get chocolate) as a model system. I manipulate the abiotic and biotic conditions, such as canopy height and leaf litter, that cacao seedlings are exposed to, and then examine how those treatments change endophyte community assembly. I then challenge plants with a pathogen, to see how changes in endophyte community structure affect host pathogen resistance.
This work is conducted at Barro Colorado Island, Panama, in collaboration with Dr. Allen Herre and Dr. Luis Mejía at the Smithsonian Tropical Research Institute.
This work was presented at ESA 2015. View the abstract here.
Endophyte Response to Disturbance
Colonization by foliar endophytic fungi has potential benefits for plants, including increased resistance against herbivores and pathogens, competitive ability, and drought tolerance. Because of the many potential functions of fungal endophytes, understanding how these communities respond to disturbance could have important implications for plant host health and function. However, there is little evidence describing the effects of disturbance on the aboveground plant-fungal microbiome.
In this project, I investigate a biotic and an anthropomorphic abiotic source of disturbance to endophyte communities: herbivory by leaf-mining insects and fungicide application, respectively. Leaf-mining insects oviposit in leaf tissue, where their larvae then travel and feed within the leaf until they emerge as adults. Leafminers thus have close and prolonged contact with fungal hyphae, potentiating strong interactions between endophytes and the insects. Most research to date on plant-leafminer-endophtye interactions has shown a negative relationship between endophytic fungi and leafminers, but these studies have been restricted to just a handful of host-species, which are almost exclusively trees. Fungicide is commonly used to treat fungal pathogens, but the effects of fungicide on non-pathogenic fungal endophytes is not well-understood.