Does insect pollination limit seed production in white cockle (Silene latifolia Poir.)?
Silene latifolia Poir. (white cockle or white campion) is an important weed in western Canadian agriculture. White cockle is an indeterminate flowering dioecious species having staminate and pistillate flowers on separate plants. New plants originate almost exclusively from seed. Therefore, both male and female plants are required in order for seed production to occur. Due to the dioecious nature of the species, seed production may be limited. Experiments were conducted in 2009 and 2010 at or around Saskatoon, Saskatchewan. Floral morphology and anatomy of both staminate flowers and pistillate flowers were examined. Specifically, anther and stigma development, floral nectaries, floral nectary stomata, and staminodes and pistillodes were observed and characterized in this species, using both scanning electron microscopy and light microscopy. Furthermore, field experiments were designed to evaluate whether S. latifolia relies solely on insect pollinators for seed production and if so, determine when pollination is occurring, and to establish if seed production in this species is limited due to pollination limitation. It was found that S. latifolia was predominantly insect-pollinated and pollination occurred both day and night; however, in 2010 pollination occurred mainly at night. Furthermore, female plants that were further than 4m from a compatible pollen source experienced reduced pollination levels and thereby seed production was reduced. Results of the pollination experiments suggested that seed production in S. latifolia may be limited by insect-pollination. Our results help to illustrate the role of pollination in the establishment of S. latifolia in Saskatchewan. There were clear pollination limitations for S. latifolia as a weed, however, the unique floral biology of this species, such as indeterminate flowering, quick pollen release, and potentially large seed yields, has allowed it to establish in western Canada and become an important weed on forage and minimum tillage farms.
Silene latifolia, white cockle, white campion, staminate, pistillate, dioecious, floral nectaries, stomata, staminode, pistillode, insect-pollinated, pollination, pollination limitation
Master of Science (M.Sc.)