Collaborative Research: RUI: how landscape fragmentation interferes with plant-pathogen interactions that maintain local plant diversity

Sarah Lawrence College, Bronxville NY

Investigators

Abstract

Many natural areas are being broken up into smaller fragments due to land-use changes such as suburban sprawl. Compared with larger fragments, small fragments are often extreme environments because they can experience stresses like higher temperatures, more light, and lower soil moisture. This research looks at how plants living in different sized fragments are affected by their pathogens. Interactions between plants and their pathogens are important because although pathogens are best known for the damage they cause they can also help preserve biological diversity. This is because each plant species has its own unique group of pathogens that specialize on it, and slows growth or kills just the plants they infect. This can keep any single plant species from dominating in an area. However, not all pathogens can thrive in the extreme environments found in small patches. It may be that in small patches, different types of pathogens that slow growth or kill multiple plant species indiscriminately are more common. If this is the case, they could decrease plant diversity compared with large patches. By uncovering how plants and pathogens interact in different patch sizes this work will be relevant for understanding the biodiversity consequences of breaking up natural areas, and may affect management of natural landscapes. Both lead researchers for this project are early-career faculty at undergraduate colleges, and will incorporate undergraduate students into all aspects of this work, including community outreach. Three parallel studies will be conducted to assess how plant-pathogen interactions are altered by landscape fragmentation, focusing on fungal pathogens in particular. First, researchers will bury seeds of twelve plant species in patches of different sizes at the Kansas Fragmentation Site, allowing the seeds to be colonized by potential pathogens and testing to see if the seeds remain viable after a year of burial. This will determine if seed mortality due to fungal pathogens is most influenced by ecological factors that vary with patch size, such as plant host density, plant species richness, and microclimatic conditions (such as temperature and soil moisture). Second, the fungal community from these buried seeds will be characterized using both culture-based methods and culture-independent molecular tools. This will determine whether fungal community structure varies predictably with patch size, host identity, and host density. Finally, a combination of greenhouse and field experiments will test the hypothesis that negative feedbacks (when plants "culture" host-specific pathogens in the soil surrounding their roots) are strongest in the interiors of large patches, rather than on the edges of large patches or in small patches. It is predicted that thermally stressful environments on edges and small patches will favor generalist fungi, reducing the influence of diversity-maintaining feedbacks on smaller fragments. Collectively, these studies link individual plant-fungal interactions to observed landscape patterns in plant diversity.