SHORT COMMUNICATION Population genetics of Himalayan balsam (Impatiens glandulifera): comparison of native and introduced populations Ana-Maria Nagy and Helena Korpelainen* Department of Agricultural Sciences, University of Helsinki, Helsinki FI-00014, Finland (Received 13 May 2013; accepted 3 November 2013) Background: Invasive species can interfere in the structure and functioning of ecosystems. Better understanding of the evolution of such species will be useful when planning their management and eradication. Aims: We aimed to compare patterns of genetic variability in Impatiens glandulifera in native and introduced regions. Methods: We used native samples from India and Pakistan, and non-native samples from Canada, Finland and the UK. Genetic analyses included genotyping using 10 microsatellite markers and sequencing of the nuclear ITS region. Results: Mean allele numbers from native and introduced samples were even, 8.8 and 8.5, respectively, while expected heterozygosities were higher in native samples (mean 0.738) than in non-native samples (mean 0.477). Hardy–Weinberg equilibrium testing indicated significant heterozygote deficiencies at 70% of the loci. Inbreeding coefficients were high in both native and introduced regions (range 0.201–0.726). STRUCTURE analyses showed that native samples from India and Pakistan possessed similar clustering patterns while non-native samples from the UK and Canada resembled each other. One of the four Finnish populations had a similar pattern with the UK and Canadian populations, while the rest showed similarly unique genetic compositions. ITS sequencing indicated in Pakistani samples two polymorphic sites not found in Indian samples but present in some samples from Canada, Finland and the UK. Conclusions: Distinct population genetic patterns indicate that human-mediated dispersal is important in I. glandulifera. Keywords: Himalayan balsam; invasive plants; microsatellites; population genetic structure; SNP markers Introduction Although biological invasions have attracted a fair amount of research interest, many questions remain about the dri- vers of dynamic invasion processes. In many cases, the alien species become freed from the constraints of gene flow from the parent population and from the biotic pres- sures of the former habitat, thus acquiring exceptional evo- lutionary opportunities (Sakai et al. 2001). Environmental conditions in the region of introduction are recognised to play important roles in the establishment and spread of introduced species (Willis and Hulme 2002; Lockwood et al. 2008), but the roles of post-invasion adaptation, genetic diversity and phenotypic plasticity in contributing to invasion success are not yet well understood. The Himalayan balsam, Impatiens glandulifera is a tall (1–2 m), insect- and self-pollinated annual plant, which is native to the Himalayas. It was introduced to Europe in 1839 as a garden ornamental, when seeds were sent from Kashmir to Kew Garden in England, and it was first recorded as a naturalised alien in 1855 (Beerling and Perrins 1993). Thereafter, I. glandulifera has become widespread throughout Europe (Beerling and Perrins 1993), and it occurs also in North America and New Zealand as an invasive plant (Weber 2003). I. glandulifera was transferred to Finland in the late 1800s and the first naturalised populations were observed in the southern part of the country in 1947 (Kurtto 1996). The success of I. glandulifera may be due to its popularity as an ornamental garden plant, its rapid growth rate and large size (the tallest annual plant species occurring in Europe), a good ability to survive heavy frost, and high seed production (Perrins et al. 1993). Ecological studies have shown that it is a strong competitor with highly plastic responses in regions of introduction (Skalova et al. 2012). The present study provides a first comparison of the population genetics of I. glandulifera within some native and non-native regions of its distribution range. Inclusion of wider sampling in the future will provide more detailed knowledge of the patterns of introduction. Previous published genetic studies have utilised I. glandulifera samples from only non-native regions (Provan et al. 2007; Walker et al. 2009; Zybartaite et al. 2011). In this study we examined patterns of genetic varia- bility in I. glandulifera both in the native distribution range and in the area of introduction. We hypothesised that (1) plants in the area of introduction possess low levels of genetic variation due to a small number of invaders and consequent effects of genetic drift, and (2) founder dynamics combined with commercial seeds from various sources has generated a discontinuous genetic structure among populations within the area of introduc- tion. Since I. glandulifera has been used as a garden ornamental, the combination of natural and anthropogenic dispersal may best explain its genetic structure in the area of introduction. *Corresponding author. Email: helena.korpelainen@helsinki.fi Plant Ecology & Diversity , 2015 Vol. 8, Issue 3, 317–321, http://dx.doi.org/10.1080/17550874.2013.863407 © 2014 Botanical Society of Scotland and Taylor & Francis