Morphological variation within and among six populations of Trillium erectum in southern Ontario

Abstract

Phenotypic variation within populations and among populations was examined in six populations of Trillium erectum from southern Ontario. The general symmetry of the flower was confirmed, although there was a tendency for the lower petals and sepals to be longer than the upper ones. Within populations, variation related to the overall expansion of the aerial shoot after emergence from the soil accounted for most of the variation. However, the expansion of the shoot was not uniform and independent growth components were found for the floral and vegetative variables. Only about one-third of the variation in floral variables was dependent on plant size. Also, within the flower, anthers, and filaments varied independently. Among-population differentiation was high and appeared to be determined by complex relationships among variables that are unique to each population. Several variables showed a correlation with underlying bedrock: populations located on Paleozoic limestone consist of plants that are smaller than those in populations located on Precambrian rocks. Whether the correlation between plant size and parental bedrock is causal is unknown.