What do we study?

How do environment, traits and symbionts determine where species live across spatial scales?

Monitoring lichen response to climate with ELON

We are a member node of the Epiphytic Lichen Observation Network, a collaboration of research groups using standardized methods to determine how lichen health and fitness respond to climate fluctuations. Our goal is to determine how lichen distributions may respond to future climate change by developing climate-driven models of lichen growth and fitness based on our low-cost monitoring of the growth of individual lichens across a spatially-extensive network of sites.

Functional consequences of lichen traits

We and many others are working toward a general theory describing how physical traits of lichens predict species’ distributions by causing differential fitness of lichen symbionts across environments. This involves linking symbiont diversity to performance and linking physical traits to their effect on three primary functional axes: water-use strategy, growth-defense tradeoffs, and dispersal-colonization tradeoffs. The development of a general and robust theory of lichen functional traits requires demonstrating these linkages across a broad suite of species and habitats, through a mixture of lab-based measurements, field sampling and transplantation experiments.

Broad-scale ecology and biogeography of North American lichens

How do species’ broad-scale distributions reflect trait-mediated environmental constraints on fitness? Water availability is a primary constraint on lichen physiology. Large-scale geographic distributions may reflect water-use traits that allow species to utilize rain, dew or humid air. We are leveraging large lichen collection data sets that span North America to evaluate whether species’ distributions reflect their functional traits and continental patterns of water-availability.

We are also analyzing spatial patterns of lichen biodiversity across multiple data sets to determine whether ecological conclusions differ among survey data that were originally collected for different purposes and which utilize different methods.

Host-symbiont interactions in environmentally-structured meta-communities

How do environmental constraints on mutualistic symbionts affect the structure of host communities? The answer should depend on which species interact (i.e. the association network), how strongly the environment limits persistence, and the degree to which interactions facilitate survival. We are developing a general simulation model that investigates the effects of host-symbiont interaction networks on biodiversity patterns along environmental gradients and are currently exploring the effect of association network structure on the model’s theoretical predictions.

As a part of this project, we (in collaboration withe the Lutzoni Lab at Duke University) are examining how algal and fungal diversity co-vary in lichen communities from different canopy micro-environments and subsequently whether diversity patterns can be used to infer environmental constraints. We are actively seeking additional collaborations with scientists who are interested in using the model to determine whether their empirical biodiversity data indicate environmental limitations on hosts versus symbionts.

Ecology of endolichenic fungi in Oakmoss lichen

Endolichenic fungi are fungi that live inside lichens and we currently know very little about their ecology and what factors constrain their distributions. In collaboration with a research course at Stanford University, we are examining the diverse fungi that live inside Oakmoss lichen (Evernia prunastri), a common lichen in California. We are particularly interested in the effect of environment, landscape spatial structure, and lichen host traits on endolichenic fungal diversity and the distributions of particular fungal species.