PARENT SESSION
Contributed Oral Session 78: Evolutionary Ecology: Genetics
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 516 D, Level 5, Palais des congrès de Montréal

Selfing reduces photosynthetic function in Datura wrightii (Solanaceae).

Tyler, Anna^*,, Bronstein, Judith, Davidowitz, Goggy, Huxman, Travis,

ABSTRACT- Datura wrightii is a large, herbaceous, desert perennial that can open as many as 50 showy, nectar-rich flowers on a single plant. The plants produce many of these flowers during the late-spring to mid-summer dry season. Despite the costs these plants must incur in producing the blooms, D. wrightii is highly self-compatible, and selfed flowers have equal fruit- and seed-set to outcrossed flowers. To elucidate D. wrightii's investment in pollinator attraction, we investigated the potential for inbreeding depression by comparing selfed to outcrossed progeny in terms of germination success and photosynthetic function. Surprisingly, seeds from selfed crosses had a faster rate of germination and a higher proportion of germinated seeds than outcrossed seeds. Evidence for inbreeding depression, however, was apparent in the photosynthetic response. When compared to outcrossed seedlings, selfed seedlings had a 36% decrease in photosynthetic rate, a 62% decrease in stomatal conductance, a 30% lower carboxylation efficiency and a 6% reduction in quantum efficiency. Further, these functional differences between the selfed and outcrossed plants were magnified when the seedlings were subjected to mild water stress. These reductions in efficient carbon gain are particularly important in a desert plant, and help to explain D. wrightii's large investment in traits to attract pollinators.

Key words: inbreeding depression, photosynthesis, Datura wrightii, stomatal conductance