The goal of my research program is to better understand the functioning of mycorrhizal fungi in natural systems. One way that members of my lab group and I work towards this goal is to examine how abiotic and biotic factors interact to affect the abundance and community composition of mycorrhizal fungi and how changes in these parameters then feedback to affect the performance of host plants. We combine field and laboratory experiments with microscopic and molecular analysis of ectomycorrhizal and arbuscular mycorrhizal fungal communities.

Current projects include:

A.Drought and Pinyon Ectomycorrhizas. Predicted climate changes include increases in drought frequency and severity, a change we are already witnessing in the southwest. We are comparing the ectomycorrhizal fungal community composition of pinyon pines before and during drought while also incorporating variation among trees in herbivory, mistletoe parasitism, interspecific competition and the presence of nurse plants. The importance of variation in ectomycorrhizal community composition to pinyons is assessed using greenhouse experiments.
B.Host Plant Genetics and Mycorrhizal Fungal Diversity. Is the genetics of the host plant or the environment more important in determining the community composition of mycorrhizal fungi? We are investigating the relationship between genetic variation within a host plant species or hybridizing complex and the species richness of mycorrhizal fungi using cottonwoods as a model system because of the extensive tree genetic data base established by T. Whitham and colleagues, and the ability of cottonwoods to form mycorrhizal associations with both arbuscular and ectomycorrhizal fungi.
C.Vertebrates and Mycorrhizal Fungi in Tropical and Temperate Zones. Vertebrates may interact with mycorrhizal fungi in a number of ways, including acting as spore vectors. We have been examining the relationship between ground-dwelling vertebrates and arbuscular mycorrhizal fungi in tropical forest for several years and also are currently examining the relationship between ectomycorrhizal fungi, squirrels and thinning and burning treatments in local ponderosa pine forests.

This faculty member is also a mentor in the NSF IGERT graduate training program: NAU’s IGERT PhD program seeks to identify key links between genes and the environment and is designed to train exceptional graduate students in molecular genetics, environmental sciences, and spatio-temporal modeling.

The research in my lab group includes two major projects that incorporate a “genes to ecosystems theme”.  First, we are part of the FIBR project (NSF Frontiers in Integrative Biological Research) led by Tom Whitham that maps ecologically important traits onto the cottonwood genome, studies their effects on associated communities of arthropods and microbes and quantifies their heritability. Our focus in on the mycorrhizal fungi associated with cottonwood roots and the endophytic fungi associated with cottonwood bark.  Cottonwoods are particularly interesting because their roots are colonized by both ectomycorrhizal and arbuscular mycorrhizal fungi, allowing us to assess the impacts of host plant genetics on two taxonomically different, but functionally similar groups of fungi.  We supplement field work with experiments in common gardens and the greenhouse.  We assess fungal community structure using a combination of morphological and molecular analyses.

With NSF funding, we have also been examining the importance of genetically-based insect herbivore resistance traits in pinyon pines to belowground communities with an emphasis on ectomycorrhizal fungi.  Insect resistant and susceptible trees differ markedly in the abundance and community composition of their mycorrhizal associates and current work is targeted at understanding how these relationships are impacted by ten years of drought.  We are also studying the consequences of these community shifts for pinyon growth and nutrient uptake. We are currently setting up common gardens to better understand genetic vs. environmental influences on pinyon pine and its associated fungal communities.