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Taz Mueller

Research Q & A

What’s your hometown?

Boulder, Colorado

What are you currently working on?

The Bell Museum graduate student award through the Dayton Fund allowed me to conduct an extensive field survey of foliar fungal endophyte communities (diverse, benign fungal microbes living in plant leaves) in Clarkia xantiana ssp xantiana, a narrowly endemic annual wildflower native to the southern Sierra Nevada foothills. This past summer (May–July 2019), I traveled the span of Clarkia xantiana’s range, and was able to collect leaf samples from more than 1,200 individuals, across 50 discrete population sites, with the goal of characterizing the communities and discerning the biogeography and spatial structure of endophyte communities across the plant’s range, as well as the diversity of endophyte communities between individuals, within populations, and between populations. From my survey sites, I also sampled two other co-occurring flowering herbaceous plants (Clarkia unguiculata, a congeneric wildflower, and Marah horridus, an herbaceous annual vine in the Cucurbitaceae) to determine how host-specific these communities are to C. xantiana. During this survey, I was also able to collect seeds from six populations to begin setting up my next experiment, a reciprocal transplant experiment that will quantify the relative effects of host genotype and environment on the microbial community assembly of leaf endophytes.

How are you working toward that goal?

I am currently working on extracting DNA from my leaf samples in order to prepare them for high-throughput sequencing to characterize the communities in the leaves. In November, I planted my reciprocal transplant experiment, with six sites spanning to environmental variables: precipitation rate and soil type. I planted 9216 seeds across the six sites this November, with 288 plants from each population at each site, and have just returned from a visit to my field sites where I collected data of seedling germination rate and size for all of the replicates.

Why are you focusing your work in that area?

I am interested in how ecological and evolutionary forces shape plant-microbial interactions, and how those interactions vary across space and time. There is very little experimental fieldwork that has quantified the effects of factors other than distance in the assembly of fungal endophyte communities in plants. I aim to clarify how host variation—through local adaptation, genetic structure and phenotypic plasticity—interacts with abiotic environmental conditions to structure how microbial communities assemble themselves within their leaf tissue. My work will provide a key empirical foundation for understanding the relative influence of host genetic and environmental effects on microbial community assembly, in a naturalistic field context. A solid foundation in the eco-evolutionary mechanisms of microbial community assembly is a prerequisite to a great deal of experimental and applied work involving relationships of plants and microbes, and these experiments will lay fundamental empirical groundwork informing future research on plant host-associated microbial communities, such as predicting how plants’ responses to climate change may be mediated by their microbial communities.

Where are you working on research/field work?

My field sites span an 80 km area within the Kern Canyon in Kern County and Tulare County, in the southern Sierra Nevada foothills of California. My bench work is being conducted on the UMN Twin Cities campus in St. Paul in the lab of my advisor, Dr. David Moeller, in the Department of Plant and Microbial Biology. I am also working with the UMN Genomics Center to use high-throughput Illumina amplicon sequencing to characterize the microbial communities in my samples.

What will your next steps/research be?

I will continue to extract DNA from my summer samples and begin the library preparation and sequencing process this spring of 2020. Throughout May and into June, I will continue to take plant fitness measurements for my current transplant experiment up through June, at which point I will sample leaves from the study plants and prepare them for DNA extraction and subsequent sequencing. Following the analysis of these communities, I will be beginning work exploring how host trait variation (namely, anthocyanin production) mediates microbial community assembly of endophytes. I will be doing this work on the other C. xantiana subspecies, Clarkia xantiana ssp. parviflora, as it is a self-compatible species. The genome of this subspecies has been sequenced and is currently undergoing transcriptomics and annotation. Our lab has been developing 200 recombinant inbred lines of C. xantiana ssp. parviflora, which I will use in field experiments to determine how variation in gene-based host traits reflects variation in host microbiomes.