PARENT SESSION
Oral Session #65: Evolutionary Ecology/ Population Genetics. Presiding: G. Gerrish.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Hall of Ideas J.

Inbreeding and nitrogen-use-efficiency in plants: linking evolutionary genetics to ecological processes.

Lonsdorf, Eric¹, ¹

ABSTRACT- Habitat destruction and fragmentation increase extinction probability for many plant species. Fragmentation increases the likelihood of inbreeding within populations, and inbreeding depression in the form of reduced seed set and biomass is well-documented. In this report, I employ nitrogen-use-efficiency (NUE) as a measure of inbreeding depression. This allows one to link evolutionary genetics with resource-based ecological models to explore the evolutionary ecology of fragmentation in plant communities. In a greenhouse study, I compared the carbon-to-nitrogen ratio (a measure of NUE) of outcrossed individuals of Nemophila menziesii (Hydrophyllaceae), an herbaceous annual native to California, to selfed individuals in low and high-nutrient environments. Results of an analysis of variance indicated that selfed individuals suffered a reduction in NUE when compared to outcrossed individuals (C/N_in = 19.7; C/N_out = 23.2; p = .02, N = 80). There was an interaction between inbreeding and nutrient level (p = 0.05, N = 80) such that outcrossed plants showed a significantly higher NUE under low nutrient levels than outcrossed individuals in high nutrient conditions; whereas, inbred plants showed little or no response to nutrient condition. Increased inbreeding resulting from habitat fragmentation may therefore alter the response of plants to competitors and other stressers. I suggest that fragmentation alters ecological processes via evolutionary change.

KEY WORDS: nitrogen-use-efficiency, inbreeding depression, habitat fragmentation, evolutionary ecology