Individual flower demography, floral phenology and floral display size in Silene latifolia

Flowers, as repeated modules on a plant, may show population dynamics that correspond to ecological models for population growth. We hypothesized that rate of flower production (birth rate), number of open flowers per day (population size) and flower duration (longevity) should be related to plant resource status. With dioecious species, resource demands of male or female function would contribute to sex-specific floral demographics. For example, fruit production in females imposes a resource cost that is absent in males. We recorded individual flower dynamics for 1200 flowers on 85 female plants and 11,179 flowers on 94 male plants in the dioecious species Silene latifolia. For males, resource availability was manipulated by defoliating a subset of plants (1587 flowers on 18 plants). For females, resource availability and usage was manipulated as follows: 0% pollinated (401 flowers on 16 plants), 50% pollinated (118 non-pollinated and 131 pollinated flowers on 17 plants), 100% pollinated (470 flowers on 46 plants) and 100% pollinated and defoliated (80 flowers on 6 plants). Populations of flowers on individual plants showed a good fit to the logistic population growth model. Estimated carrying capacities for flowers decrease with decreasing resource availability (males > defoliated males > 0% pollinated females > 50% pollinated females > 100% pollinated females > 100% pollinated and defoliated females). Pollinated flowers had shorter longevity than non-pollinated flowers. Non-pollinated flowers on plants with 50% pollination had shorter longevity than non-pollinated flowers on plants with 0% pollination. Thus, flower population dynamics within plants do show evidence of resource-based dynamics.