Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Biology Dept.


Judy L. Stone


The annual herbaceous plant Impatiens glandulifera Royle is native to the Himalayas and is a significant invasive species in Europe. In the past century, it was introduced to the United States, where it has become established in 12 states. This study evaluated genetic differentiation among four Maine populations, to address a theory that posits hybridization of distinct lineages as a trigger for invasiveness. Regions of microsatellite repeats were evaluated at two polymorphic loci for 41 plants sampled from the four populations. A striking finding was that the observed heterozygosity was substantially higher than the heterozygosity expected from random combination of alleles. Our data suggest that the populations have already hybridized, either in North America or elsewhere in the introduced range, resulting in inflated heterozygosity due to hybrid vigor or fixed heterozygosity. We expect that the lag time following introduction is at an end and that I. glandulifera will soon become invasive and undergo significant expansion in the eastern United States.


invasive species, population genetics, hybridization, lag time, microsatellite