Differences in cold hardiness between introduced populations of an invasive tree

Abstract

The potential for populations of exotic invasive plants to differ in their response to stressful environmental conditions is an underexplored issue in determining invasive species’ range limits. Introduced genotypes may differ in response to climatic, edaphic, or biotic factors within their introduced range leading to differences in potential ranges among populations. We examined differences in cold hardiness (resistance and tolerance to winter conditions and freeze events) among Chinese tallow tree (Triadica sebifera (L.) Small) seeds and seedlings from two genetically distinct populations in the northernmost portion of its introduced U.S. range (North Carolina and South Carolina). Seed germination from these two sources was compared between fall plantings (mimicking natural dispersal timing) and spring plantings (occurring post-frost) as well as among areas within and inland of Chinese tallow’s core coastal distribution in South Carolina. Overwinter seedling survival and damage were also assessed among seedlings planted in the piedmont of South Carolina and following artificial freeze events in the lab. Seeds and seedlings from South Carolina sources showed greater reductions in germination success by inland winters, greater winter damage in field plantings in the piedmont, and lower survival after prolonged freezes than those from North Carolina. These results indicate that differences in cold hardiness exist among introduced populations of Chinese tallow and suggest that genotypes from North Carolina possess greater potential for expansion into areas with more severe winters. Differences among introduced populations should be considered when evaluating the potential range expansion of Chinese tallow and other invasive species.