I am interested in the intersection of predation, competition, dispersal, and invasion – as well as the role of random chance – in determining biological diversity, primarily in extreme environments. I have published research on the diversity and dynamics of viruses, bacteria, microscopic animals such as rotifers and tardigrades, and pocket mice, bunchgrasses, and trees. See my Google Scholar page for my most up-to-date list of publications.
Seasonal processes in the evolution of Arctic soils
I am currently a co-investigator on a collaborative effort to understand the unique role of extreme polar seasonality on the development of soil. As glaciers retreat due to a warming climate across the Arctic, they expose new soil that is typically very low in carbon, nutrients, and living things. Over time, bacteria, fungi, and microinvertebrates and algae colonize the soil, and eventually plants move in. But the long polar night – which can be three months – followed by months of snowmelt provide a uniquely challenging environment for microbial life, as well as unique opportunities for life. This project will install sensor arrays in the soil along a transect of soil age at the toe of a retreating glacier in Svalbard, Norway, to monitor the timing of temperature and liquid water at various depths. My role, as a biologist, will be to sample the total DNA of potentially active organisms and the RNA of currently active organisms in the soil across four seasons. Due to the global pandemic, fieldwork planned for this project in 2020 has been postponed to 2021. This project is supported by the National Science Foundation’s Signals in the Soil initiative.
Microbial community assembly and function in Antarctic cryoconite holes
Cryoconite holes are small puddles that form in glacial surface ice when dust lands on it and the dark material absorbs sunlight, melting the ice beneath it. Entire ecosystems form and grow in these holes, with photosynthesizing algae and bacteria supporting microscopic animals such as rotifers and tardigrades (“water bears”). I work as part of a team to use these unique ecosystems as an interconnected of “natural test tubes,” both to examine the patterns of biological diversity that form naturally in them, and to create them experimentally to learn the importance of random change relative to biological and physical processes. The fieldwork was carried out over the course of three austral summers from November to February of 2016-17, 2017-18, and 2018-19. I was fortunate enough to deploy to the ice for all three seasons. Laboratory processing has wrapped up, and although we have published several papers on our findings, the analysis and writing continues. Learn more about the project blog (cryoholes.wordpress.com). This project is supported by the National Science Foundation’s Office of Polar Programs.
Effects of an invasive grass on the Sonoran Desert
In my doctoral research, I studied how predation and resource competition interact to determine species diversity, especially in the case of species invasions. I specifically focused on how buffel grass (Pennisetum ciliare), which had been introduced from Africa to North America, suppresses the regeneration of long-lived native plants where it spread. I looked at whether the adult grass prevented native seeds from germinating and seedlings from establishing, and whether it did so through resource competition or through increasing the abundance of rodents that eat native seeds. The rodents eating native seeds in areas that buffel grass invades, however, act not only as consumers, but as seed-dispersers by burying them in shallow caches outside their burrow. To find out whether the rodents were burying seeds more often under buffel grass because its dense canopy provided better hiding places from owls, I used fluorescent powder to locate caches. Finally, I asked how the cover-seeking behavior to avoid predators might affect the diversity of the rodents themselves, especially if grass cover increased their effectiveness at hiding. Since there were no robust theoretical predictions for this, I used simple consumer-resource models to determine when predator avoidance behavior would increase or decrease the ability of the avoiders, who also compete for resources, to coexist. This project was supported by the Western National Parks Association, Garden Club of America’s Award in Desert Studies, and the Graduate and Professional Student Council’s Research Grants.