Life History Studies on the Genus Trillium (Liliaceae) III. Reproductive Biology of Six Sessile-flowered Species Occurring in the Southeastern United States with Special Reference to Vegetative Reproduction

Abstract Life history characteristics, e.g., stage class structures of natural populations and associated reproductive characteristics, were studied for six sessile-flowered, diploid Trillium (Liliaceae) species that are restricted to the Coastal Plain region of the southeastern United States.
These sessile-flowered species reproduce primarily by vegetative propagation. Leaf area measurements were used to categorize stage class distributions of natural populations. Populations propagating mainly by vegetative reproduction had non-sigmoidal, convex-shaped population structures with most plants being in the intermediate stage classes. Low numbers of individuals in smaller stage classes and an abundance of intermediate sized individuals are due to the fact that vegetative propagules are the primary method for maintenance of local populations.
Characteristics associated with sexual reproduction were also examined. Seed output averaged about 20 seeds per plant, except for T. lancifolium which produced 9.7 seeds on the average. Seed setting rates varied between 15.61–44.15% and mean seed weight varied from 4.89 to 10.75 mg. The dominance of vegetative versus sexual reproduction may be due to the fact that all six species occur in ecologically unstable flood plain habitats.