Great Lakes Dune Research

A driving interest for much of my research has been the role of microbial mutualists in community and ecosystem processes. Many of the current theoretical underpinnings of plant community ecology are based on negative species interactions, mainly competition and herbivory. However, most plants interact with mutualists at some stage of their life cycles. Fungal endophytes within the genus Epichloë associate with ~20%–30% of grass species and have been shown to have strong effects on plant communities. For my dissertation I focused on the effects of a fungal endophyte, Epichloë amarillans, associated with the dominant grass species, Ammophila breviligulata, on nutrient cycling, below-ground microbial community, and plant-plant interactions.


How does a fungal endophyte affect decomposition in the Great Lakes Dunes?

Fig. 1 Bell-Dereske v2
Fig. 1 from Bell-Dereske et al. 2017

Using litter bag, I found that the endophyte presence in litter increased initial rates of decomposition, though the effect disappears after one growing season. Later decomposition of litter was slowed by endophyte presence in A. breviligulata conditioning the soil microenvironment.

Bell-Dereske, L., Gao, X., Masiello, C. A., Sinsabaugh, R. L., Emery, S. M., and Rudgers, J. A. 2017. Plant-fungal symbiosis affects litter decomposition during primary succession. Oikos. 126: 801-811



Endophyte_belowground effects
Schematic of pathways that Epichloë may affect dune below-ground microbial community

What are the effects of a fungal endophyte on belowground microbial communities? 

Using microscopy and 454 pyrosequencing, I found that the endophyte reduced the abundance of soil fungi and the diversity of an important fungal group, arbuscular mycorrhizal fungi, though the effect on diversity disappeared when we altered precipitation. The presence of the endophyte also shifts the positive relationship between root-associated bacteria and soil moisture to negative where diversity decreased with increasing soil moisture.

Bell-Dereske, L., Takacs-Vesbach, C., Kivlin, S. N., Emery, S. M., and Rudgers, J. A.. 2017. Leafendophytic fungus interacts with precipitation to alter belowground microbial communities in primary successional dunes. FEMS Microbiology Ecology 93:fix036-fix036.


What are the effects of a fungal endophyte and climate change on plant community interactions?

Exploring endophyte effects on plant-plant interactions and the community’s response to extreme rain events, I used a comprehensive field experiment manipulating plant intra- and inter-specific competition, endophyte presence, and precipitation regime factorially. This experiment required planting 4860 individuals of six dune plant species, designing a solar-powered irrigation system to impose precipitation manipulations, and altering lake water chemistry to match that of natural rainfall. I found that the fungal endophyte altered plant community processes by increasing the negative effects of interspecific competition for its host, A. breviligulata, and a dominant competitor grass while decreasing negative interspecific effects for the rest of the plant community. Additionally, increased precipitation reduced negative interspecific effects.

Visual surveys of the plant cover in DECISIVE (Dune Endophyte Competition Interaction Storm Intensity Variability Experiment) plots

Here is a video of me discussing this research!