Ragweed is an abundant weed in southern Ontario, but becomes increasingly rare at more northern locations until it disappears entirely somewhere in northern Ontario. Plants near the edge of its range may escape many of the natural enemies (herbivores and pathogens) that attack it further south, potentially benefitting marginal populations. These same marginal populations are likely to spread north in response to a warming future climate; escape from enemies might assist in this spread. We are investigating whether natural enemies have a weaker effect in marginal (northern) vs. central (KSR) populations of this species and related exotics. Our results may help to predict how rapidly this species is likely to invade new areas in future.
Dasvinder Kambo, Ecology & Evolutionary Biology, University of Toronto