When flowers first open, stigmas are presented for several days after which the anthers come forward in close proximity of the stigmas and start shedding pollen. Delayed autonomous selfing could be valuable in ensuring seed set, especially in the small patchy populations typical of Aquilegia canadensis. Moreover, stigmas typically recieve little of no pollen before anther dehiscence, indicating that the rate at which outcross pollen arrives on stigmas is low. However, eliminating the capacity for delayed selfing by removing anthers from flowers does not reduce seed set in natural populations, even at low plant densities. This suggests that sufficient outcross pollen is deposited on stigmas for full seed production and that the reproductive assurance provided by delayed selfing may be of little selective value.
Some taxa are strictly sexual and outcrossing.
Others have evolved predominant self-fertilization. The relative importance of sexual and asexual reproduction has a variety of ecological and evolutionary consequences, especially in terms of genetic diversity. Often closely related groups of sepecies include both sexual and asexual taxa. Some species, such as Antennaria parlinii, contain both sexual and asexual individuals. We have been studying the extent to which populations are differentiated in terms of sexuality, and the association between asexuality and other life history traits.