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Abstract Detail

MSA - Ecology/Pathology

Hersh, Michelle [1], Vilgalys, Rytas [2], Clark, James S. [3].

Fungal symbionts of tree seedlings and the Janzen-Connell hypothesis.

Plant community ecologists frequently use the Janzen-Connell hypothesis to explain high levels of tree diversity. This hypothesis posits that host-specific natural enemies control populations of tree seedlings, and that these enemies occur more frequently when seedling densities are high, seedlings are close to conspecific adults, or both. We explore this hypothesis using a dataset of symbiotic fungi collected from dead and living seedlings of six temperate tree species in a North Carolina mixed hardwood forest. Many of the fungi collected are capable of multiple lifestyles; we focus on fungi with the most potential to act as pathogens. We employ a hierarchical Bayesian model of fungal impacts on seedling survival, involving a model selection framework (reversible jump Markov Chain Monte Carlo) that allows us to evaluate how combinations of fungal symbionts affect survival without assuming that these effects are additive. We find that although most common fungal symbionts can be isolated from multiple hosts, their effects on survival are not equal. Three fungi tested have negative impacts on the survival of certain hosts and no impacts on others; others have minimal impacts on all hosts. In two hosts, negative impacts of the tested fungi on seedling survival only become apparent when two of the tested fungi are found in combination in a single host individual. We address these results in the context of the Janzen-Connell hypothesis, but also consider other ways in which these multihost fungi may impact plant diversity. We also discuss how this modeling framework can enhance understanding of the ecological functions of symbiotic fungi capable of multiple lifestyles.

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1 - Duke University, University Program in Ecology, Box 90338, Durham, NC, 27708, USA
2 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
3 - Duke University, Nicholas School of the Environment, Box 90328, Durham, NC, 27708, USA

community ecology
disease ecology
forest ecology
plant-fungus interactions
opportunistic pathogens.

Presentation Type: Oral Paper:Papers for Topics
Session: 44
Location: Cottonwood B/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 10:45 AM
Number: 44003
Abstract ID:827