Seed and Seedling Ecology of Acer saccharum and Acer platanoides: A Contrast Between Native and Exotic Congeners

The exotic tree, Acer platanoides, is increasing in forests of northeastern North America, largely within the range of its native congener, Acer saccharum. A combination of field and controlled experiments was used on seeds and seedlings of these congeners to determine species characteristics that may be contributing to these floristic changes. Acer platanoides experienced lower rates of seed predation than A. saccharum in field experiments. Differences in the dispersal and allocation characteristics of the two species were small and not likely to explain the relative success of A. platanoides. Greenhouse- grown seedlings of A. platanoides were much larger than those of A. saccharum because of differences in seed size, not differences in growth rate. These data suggest that preferential seed predation and initial seed size differences may explain greater relative success in Acer platanoides seedlings