The evolutionary advantages of producing both chasmogamous (CH) and cleistogamous (CL) flowers is poorly understood in many plant species. CH flowers are large, showy, and may be visited by pollinators, while CL flowers are small, closed, and self-pollinated. Because of mating system differences, the maintenance of CH and CL progeny may be influenced by inbreeding depression. This study measured the level of inbreeding depression by comparing the fitness of selfed CH and CL progeny to outcrossed CH progeny in Viola canadensis, a white-flowered violet found in beech-maple forests. Pollinations on CH flowers were conducted in the greenhouse in Spring, 1997, and CH treatments consisted of self and outcross hand-pollinations and an unemasculated control. Seeds from CH and unmanipulated CL flowers were counted and weighed. No significant differences in the number of seeds per capsule were found among treatments. Autonomously selfed CH seeds (control) had similar seed mass to hand-pollinated selfed CH seeds, indicating that the pollination technique itself did not affect seed set. CL seeds had higher mean seed mass (1.71 mg) than CH self-pollinated seeds (1.56 mg), and CH outcross-pollinated seeds (1.43 mg). All differences were significant, indicating that inbreeding depression was not apparent at the seed stage. The apparent absence of inbreeding depression may be indicative of a history of selfing and/or a deficiency of inter-population gene flow in V. canadensis. Research is continuing to determine if inbreeding depression appears in later life cycle stages such as germination and seedling survival.

Key words: chasmogamy, cleistogamy, inbreeding depression, mating system evolution, Viola canadensis