Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Both monocarpic and polycarpic phenotypes occur in populations of Artemisia campestris growing on the sand dunes at Pinery Provincial Park, Ontario. Populations in three habitats differing in seral age, vegetation cover, vegetation type and proximity to the lake were selected for study. The distribution of phenotypes within and among populations, genetic control of the character and the relationship between number of reproductive events and age-specific survivorship were examined. Emergence patterns, fecundity, impact of herbivores, rosette diameter and growth patterns were also investigated.;Established plants within populations were mapped and tagged. Permanent plots were established to study seedling recruitment and to augment sample size. To determine if polycarpy was under genetic control, plants were grown under uniform conditions at two locations and a reciprocal transplant-replant experiment was performed.;The degree of polycarpy found was small and limited to one habitat, the heavily vegetated "transition zone". The ratio of juvenile to seedling survivorship was close to 1 in this habitat. Fecundity and emergence were both low, and plants were smaller at flowering than plants from other habitats. On the dune ridge, the survivorship ratio was also close to 1. Emergence was low and fecundity intermediate. The plants on the dune ridge were larger, grew more rapidly and the critical rosette diameter for flowering was larger. Growth was also less affected by herbivores than in the other two habitats. Although repeated flowering was never observed, postflowering vegetative survival did occur. In the third habitat, the slack, mortality increased with age, and was higher than in the other habitats. Emergence was highly variable and fecundity was high.;Results from the uniform garden treatments suggest that plants from all habitats have the potential for polycarpy. Polycarpy was thought to be maintained by the indeterminate growth pattern of the species, by selection of individuals with low fecundity during the first flowering season that could flower again, and by gene flow among populations.



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