Local and regional drivers of lichen diversity in U.S. forests

The number of species in a local community is influenced by regional processes that alter the pool of species able to colonize a site as well as local processes that filter which species establish and persist upon arrival. A species’ local persistence will depend on whether environmental conditions meet fundamental niche requirements and the availability of sufficient niche space. Thus, both environmental optimality and habitat heterogeneity can potentially increase local richness within a group of species with comparable niche requirements. I am interested in whether lichen epiphyte communities in forests are primarily influenced by regional versus local processes, and whether the  local forest environment increases species diversity by providing more niches or more optimal conditions.

Trait diversity and the assembly of lichen communities on trees in North Carolina forests

Are some lichen communities on trees limited by the environment they experience on the trees surface, while other lichen communities are more influenced by how long the tree has been providing a potential habitat? What about competition between lichens- does it happen more on trees with certain characteristics?  The goal of this project is to measure the traits of lichens living on different trees in order to understand how the relative importance of various processes structuring communities on different trees changes as a function of the physical environment provided by the tree (e.g. bark properties, substrate age, light availability).

Lichen communities and microclimatic gradients in tree canopies

The environment that lichens experience within tree canopies can change markedly depending on whether a branch is exposed to light or sheltered among the leaves. In this project, I get to climb trees in order to determine whether lichens in communities in different parts of the canopy have traits that vary with measured environmental differences. Furthermore, I am testing whether this variation in traits occurs because different species occupy different parts of the canopy or because species are able to alter their traits in order to better survive in their environment.

punctelia_rudecta_personal_websiteAlgal and fungal diversity of lichens in tree canopies

Lichens are a unique system in which to study ecology because they are comprised of a symbiosis between fungal and algal species. As a part of my canopy lichen sampling, I recently received a grant to study how algal and fungal diversity co-vary in lichen communities from different canopy micro-environments. I am developing a model of symbiotic communities that will allow us to interpret whether these data show that the environment limits one partner  more than the other.

Past Projects

Dimensions of Biodiversity Distributed Graduate Seminar

Throughout the 2011-2012 academic year I was the student lead on a research seminar exploring the taxonomic, functional and phylogenetic diversity.  At UNC, our seminar team has investigated geographic variation in all three dimensions of biodiversity in two contrasting data sets of eastern North American tree communities; the Carolina Vegetation Survey, which focuses on intensively sampling native plant communities in the southeastern United States, and the Forest Inventory and Analysis national program, whose goal is to assess the current state of U.S. forests through broad scale stratified random sampling.  The Dimensions of Biodiversity Seminar website can be found here.


  • Our group’s research was published in Ecography! Click here to see the article.
  • Biodiverse Perspectives, a new graduate student blog on foundational and frontier papers in biodiversity science has just launched as a result of the effort of  grad students in DBDGS.

Diversity of core and transient species in North American bird communities

Magurran and Henderson (2003) suggested that species in communities can be partitioned into ‘core’ species that are persistent through time at a local site, and ‘occasional’ species that occur infrequently.   A natural question that arises from this division is what factors influence the number of core versus occasional species that occur at a site.  White and Hurlbert (2010) hypothesize that, in North American bird communities, core species richness should be limited by environmental conditions whereas occasional species richness should be influenced more by enrichment from the regional species pool.  We are testing this hypothesis using long-term point-count data from the North American Breeding Bird Survey.

Magurran, AE and PA Henderson. 2003. Explaining the excess of rare species in natural species abundance distributions. Nature 422(17): 714-716

White, EP and AH Hurlbert. 2010. The combined influence of the local environment and regional enrichment on bird species richness. Amer. Nat. 175(2)


Dr. Allen Hurlbert, Univeristy of North Carolina, Chapel Hill
Dr. Ethan White, Utah State University