For ESA 1998 Annual Meeting :
MORRISON, JANET A. The College of New Jersey, Ewing, NJ 08628 USA. Ecological amplitude for light in the invasive forest plant Alliaria petiolata.
Alliaria petiolata stands can be found on the forest edge where sunlight (PAR) is an order of magnitude greater than at interior stands. I stratified seed from edge and interior stands in the New York Botanical Garden Forest, grew seedlings in pots in a greenhouse until late spring, and then placed them into an outdoor experiment under sun or shade cloth. Leaf area was measured before placement and in October. ANOVAs indicated that plants originating from the forest were larger after the greenhouse period, and that subsequent growth outdoors was much greater under shade regardless of plant origin. There were also significant differences among seed families in summer growth. Alliaria’s ability to utilize different light levels appears to be due to a plastic response to light rather than genetic differences between edge and interior individuals, so that edge stands can be the source of invasion to the interior. Interior plants are divergent from edge plants in their ability for more rapid early growth in the period before the canopy leafs out. The variation among families for growth supports the possibility that there is genetic variation in the population on which natural selection may act, although further work needs to be done to rule out maternal effects.