PARENT SESSION
Organized Oral Session 3: Plant Pathogens in Nature: Rethinking Vegetation Dynamics
Organized by: CM Malmstrom and A Power
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 205.

Plant pathogens and vegetation dynamics in natural systems: central questions.

Malmstrom, Carolyn^*,1, ¹ Michigan State University, East Lansing, MI

ABSTRACT- Alterations in pathogen and vector dynamics can cause sudden and dramatic changes in plant community structure. For instance, some of the more notable responses of vegetation to climate change are likely to be driven by change in disease epidemiology. Predicting how disease epidemiology in natural systems will respond to perturbation requires that we have a baseline understanding of the ecological effects of pathogens. Often we do not. This presentation introduces the session on plant pathogens in nature by discussing three questions that are central to our understanding of plant pathogens and natural vegetation dynamics: (1) How important are plant pathogens in natural systems? Are they detail agents driving small adjustments in systems shaped by other forces, or more potent regulators? How much of what has been attributed to plant competition might be better seen as apparent competition, mediated by plant pathogens? How often do pathogens limit vegetation distributions? (2) Which natural plant pathogen systems do we understand the most, and which the least? Fungal, bacterial, and viral pathogens differ substantially, yet our understanding of the distributions and roles of different pathogens remains quite limited. It was only 15 years ago, for example, that researchers found that ocean waters contain high concentrations of viruses, which may help regulate phytoplankton blooms. (3) When do pathogens drive quick change in plant communities and when do they act as slow sculptors? It is commonly assumed that the greatest impacts of pathogens occur when new disease organisms enter susceptible systems, and that over time pathogens and hosts tend to co-evolve in ways that lead to moderation of disease severity. How often is this true?

Key words: disease ecology, pathogens, vegetation dynamics