The abundance and leaf morphology of three Vaccinium shrub species were measured across a gradient in abiotic conditions in British Columbia, Canada. Light levels and wind speeds decreased as soil moisture increased across transects extending from the shoreline into the forest understory. Leaf morphology varied similarly in all species across transects, presumably in response to changing abiotic conditions. Leaf sclerophylly (ratio of leaf mass to area) was higher at the shoreline in all three species. Similarly, each species had distinct abundance patterns associated with species specific values of leaf sclerophylly. Vaccinium ovatum had highly sclerophyllous leaves and was more abundant at the shoreline; Vaccinium parvifolium showed intermediate sclerophylly and peaked in abundance in transitional habitats; Vaccinium ovalifolium had lowest sclerophylly and was most abundant in forested areas. Abundance results were supported by an investigation of Vaccinium occurrence patterns on a group of near-by islands. Therefore, patterns of morphological plasticity parallel trends niche differentiation with respect to environmental conditions. These trends provide strong indirect support for the importance of adaptive morphology in promoting niche differentiation in Vaccinium shrubs.

Key words: leaf specific mass, morphological plasticity, niche partitioning, Vaccinium