PARENT SESSION
Oral Session # 33: Pathogens, Toxins, and Disease II: Plants.
Presiding: A Davelos
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 201.

Life history changes in Arisaema triphyllum due to pathogen infection.

Mason, Erin^*,1, Kampf, Katy¹, Jarosz, Andrew¹, ¹ Department of Plant Biology, East Lansing, MI, USA

ABSTRACT- Habitat fragmentation is a known risk to plant populations, particularly those with limited migration capability. The presence of a disease that lessens individual fitness may compound the problem and lead to increased local extinctions. Pathogen infections can influence plant life histories by reducing growth and survivorship, and by altering the amount and pattern of reproduction. Since 1999, we have monitored six populations of Arisaema triphyllum, a perennial forest herb, to investigate the impact of infections by Uromyces ari-triphylli, a systemic rust fungus. Effects on death and dormancy are correlated with host size. Among smaller plants, diseased individuals displayed higher rates of dormancy and mortality than nondiseased individuals. This trend diminishes as plant size increases. Infection decreases growth rates across all plant sizes. Both infected and uninfected individuals are able to reproduce asexually, yet asexual offspring of diseased plants have a lower survivorship. Disease directly limits a plant's sexual reproduction by reducing consecutive years of flowering and lowering seed output. Our data indicate that U. ari-triphylli infection consistently reduces host fitness by reversing growth patterns, limiting reproduction, and elevating rates of dormancy and mortality. Such effects on individual plants can influence entire populations. High disease incidence can alter the size, structure, and persistence of local populations. Our demographic data indicates that the size of all populations is decreasing over time, suggesting that fragmentation or some other environmental variable is negatively influencing these populations. High incidence of disease exacerbates this trend and may increase localized extinctions or endanger the species as a whole.

Key words: life history, metapopulations, Uromyces ari-triphylli, plant-pathogen interaction