A TEST OF THE ENEMY RELEASE HYPOTHESIS: COMPARISON OF INSECT AND FUNGAL DAMAGE TO LEAVES OF YOUNG, EXOTIC NORWAY MAPLE AND NATIVE SUGAR MAPLE

Matthew Elkins, Athena Huang, Yamini Kathari, Adwiteeya Misra, John Speigel, Matthew Tse, Zixiao Wang

Advisor: Dr. Kristi MacDonald-Byers
Assistant: Jess Reid

ABSTRACT

Norway maple ( Acer platanoides ), originally introduced to North America from Eurasia as an ornamental tree, is an invasive tree in North America where it threatens to displace native trees, including the sugar maple ( Acer saccharum ). One of many possible explanations for why invasive plants such as the Norway maple may have an advantage in exotic habitats is the enemy release hypothesis (ERH), the idea that an invasive species thrives in the absence of its native enemies. Our hypothesis was that leaf samples taken from saplings of both species would show that the Norway maple suffered less leaf damage from herbivory and fungal infection than the sugar maple. In July 2009, leaves were sampled from three transects of the Drew University Forest Preserve, a Fagus grandifolia-Acer saccharum-Quercus spp. forest. Samples were analyzed to determine leaf damage in each species. Our study found slightly lower mean leaf damage for the Norway maple, but the difference was determined to be statistically insignificant. In addition, the mean leaf damage of both species was low, <6%. The results showed that the ERH likely does not play a major role in the Norway maple's invasion during the sapling stage. It is possible that specific differences between the Norway maple and the sugar maple in their ability to use resources play a more important role in Norway maple's success, and further research should investigate those differences.