Research

Fungal endophyte communities; diversity, structure and specificity across environmental gradients and plant communities

Fungal endophytes comprise one of the most ubiquitous groups of plant symbionts, inhabiting healthy leaves and stems of all major lineages of plants. Together they comprise immense species richness, but little is known about the fundamental processes that generate that diversity and maintain their evolutionary success as plant symbionts. Community structures of foliar fungal endophytes depend mostly on host taxa and climate, but other environmental variables, such as soil type, plant physiology, neighboring plant community, are largely unexplored. Our goals are to understand how and why community structures change across environmental gradients as well as understand what ecological factors may lead to hyperdiverse communities of endophytic fungi.

Following the life cycle of an endophyte using monarch caterpillar model

Endophytes live inside leaves. Leaves get eaten by herbivores. And what happens to the endophytes? Do they survive the herbivore gut? Is there an evolutionary advantage to be eaten? Or would they rather hedge their bets on the ground on a senescing leaf? With the help of Vanessa Chou, an undergraduate research assistant (2015-19), we've been comparing the fungal community inside leaves and caterpillar frass. Our goal is to determine which species survive and may be adapted to herbivory. We will then test to see if they correlate with generalist vs. specialist endophytic lifestyles. We have been testing these in monarch caterpillars and local milkweed species of southern California. Pictured, you see dozens of retired caterpillars who produced many milligrams of frass to this research. No animals were harmed. 

Fungal endophytes of pines and related conifers

Fungal endophyte species that are horizontally transmitted appear to lack strict host-specificity, unlike many vertically-transmitted symbionts. The communities are highly variable across environments, host species, and distances, but patterns for taxon-specific affinity can be observed depending on taxon level.  We are exploring the host specificity of foliar fungal endophytes associated with the Pinus genus of North America. In particular, we are interested in how the evolutionary history of host species affects community similarity of the endophytes. We are focused on understanding coevolutionary mechanisms responsible for fungal endophyte diversity and using Lophodermium as a model system. Picture here is a potentially new species Rodolfo and Ryoko found in China.

Microbiome of Big Cone Douglas Fir

Big cone Douglas fir (BCDF) or Pseudotsuga macrocarpa is an endemic conifer in southern California with a small species range that is threatened by high-intensity wildfires. An intervention to help restore Bigcone Douglas-fir may be necessary given recent mortality rates.

Legume-rhizobia mutualism stability

Nitrogen-fixing bacteria, called rhizobia, associate with legume roots in a mutualistic symbiosis. We explore how rhizobia that poorly fix nitrogen (relative to the rest of the population) evolve, but appear to not have destabilized this classic mutualism. 

Other projects

We are also involved in various miscellaneous projects with other labs and departments outside of EEMB. For example, the D'Antonio lab and ours have been co-funding a mechanical engineering project to build a drone that will bring back fresh leaf samples! 

We also occasionally have monograph projects to describe new fungal species by collaborating with "real" mycologists with mad razor blade and microscopy skills.