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Wednesday, April 11 • 2:00pm - 2:15pm
SYMPOSIA-16: From Microbes to Landscapes: Can Plant Species Loss in Small Habitat Fragments Be Explained by Plant-Pathogen Interactions?

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AUTHORS: Cathy D. Collins*, Bard College; Michelle H. Hersh, Sarah Lawrence College

ABSTRACT: Disease plays a key role in maintaining local plant diversity, but how and why pathogen pressure varies across landscapes is not well understood. Host and pathogen distributions in fragmented landscapes reflect not only the influence of area, isolation, and abiotic factors, but also the biotic interactions between the pathogen and its host. We examined plant richness and composition, fungal-mediated seed mortality, and seed-borne fungal diversity in an experimentally fragmented landscape in Kansas, U.S.A. We buried seeds of six plant species for a year in three landscape treatments: small patches, edges of large patches, and centers of large patches. Half of the seeds in each location were treated with fungicide. We measured germination success of exhumed seeds, and cultured fungi from seeds for identification using ribosomal DNA sequencing. If plant-pathogen interactions influence landscape-scale patterns of plant community structure in fragments, we expected to see: 1) patch size differences in the composition of seedbanks, above-ground plant communities, and seed fungal communities; and 2) pathogen-induced seed mortality that depended on where in landscape seeds were buried. For seeds buried without fungicide, landscape location was the strongest predictor of germination success. Across species, seed germination was lower in small patches, where soil temperatures were more extreme. In contrast, for seeds protected by fungicide, plant richness was a better predictor of seed mortality than patch size: fungicide provided the greatest benefits where host richness was high. Both plant and fungal community structure differed with fragment size. We also found that fungi show host preferences—a necessary condition for diversity-maintaining negative feedbacks. Our results suggest that by altering plant species richness and community composition, fragmentation alters pathogen pressure on seeds indirectly via changes in host community structure. Consequently, local plant-pathogen interactions may contribute to patterns of diversity in fragmented landscapes.

Wednesday April 11, 2018 2:00pm - 2:15pm CDT
Grant Park Parlor

Attendees (4)