Document: KAT-3-55-2

Population dynamics and reproductive strategies in Arisaema triphyllum: Influence of a systemic rust pathogen, Uromyces ari-triphylli.

KAMPF, K.M.* and A.M.JAROSZ

Michigan State University, East Lansing, MI 48824 USA ¹

Abstract:
A forest perennial, Jack-in-the-Pulpit, Arisaema triphyllum, reproduces both asexually and sexually, as either a male or a female. Each individual possesses the ability to change gender multiple times throughout its lifetime. Gender is correlated with size: Small plants do not flower and reproduce clonally only, medium sized plants are males, and large plants are females. Size and gender for a given growing season are predetermined by the amount of photosynthate stored over the previous growing season in an underground corm. Infection by the systemic rust, Uromyces ari-triphylli, has the potential to alter this reproductive strategy by affecting the size, gender and persistence of infected plants. Disease is transmitted horizontally and to clonal offspring, but not vertically to sexually produced offspring. Although sexual reproduction is costly for an already diseased-stressed plant, seed derived offspring are more fit because they escape disease. The other reproduction option,asexual,is not advantageous since offspring will be diseased. As part of an ongoing demographic study investigating the effects of infection on both individuals and populations, we censused six natural populations of Jack-in-the-Pulpit, three healthy and three diseased. Preliminary results revealed infected flowering individuals were smaller than their healthy counterparts and diseased individuals were more likely to flower than healthy individuals of the same size. In addition, diseased populations had a higher proportion of flowering individuals than healthy populations. These data suggest that disease may cause a plant to invest in sexual reproduction and to do so at a smaller size than healthy individuals.

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This abstract is being presented at: 3:30 PM in session:
Poster Session #17: Vegetative Analysis.