Abstract: Invasions by non-native plants can negatively affect native biodiversity and are costly to manage. In general, the Subarctic and Arctic are less susceptible to invasions than temperate regions due to their harsh conditions and reduced human activity. However, Churchill, Manitoba (58° N, 94° W) is an important exception as it has an abnormally high number of invasive plants for its location, due to historical human activity and the presence of a grain port.
Natural landscapes in the Churchill area are exclusively dominated by native plant species, while non-native species are essentially restricted to the town. It is unclear how anthropogenic changes in town have created a suitable habitat for invasives. One possibility is that buildings and other human structures may provide shelter, creating microenvironments where invaders may survive. The goal of my project is to understand whether Taraxacum officinale (Common Dandelion), a highly invasive species, is common in the town of Churchill as a result of anthropogenic shelter.
In August 2021, I set up an experiment that tests whether anthropogenic shelter is important to T. officinale, in contrast to a widely-distributed native arctic species from the same genus, Taraxacum lacerum. I set up paired plots near several buildings: each with ten plants of both species randomly distributed within the plot, one plot facing south while the other plot facing north. In 2022, I returned to Churchill to determine if the performance of experimental plants is improved in more sheltered sites. I also extensively surveyed dandelion populations in town to understand their distribution and performance relative to their proximity to buildings. Survey results show that invasive dandelion populations mainly establish on the warmer south-facing sides of buildings.
Understanding which factors limit T. officinale’s establishment adds to the understanding of invasion risks in northern environments. If T. officinale currently is limited to warm, protected microsites, this may help to explain why it (and numerous other non-native plants) are restricted to town, and unable to invade nearby natural environments. Furthermore, this result would suggest that non-natives like dandelion may escape townsites in the future if the climate warms sufficiently, representing a serious threat to currently native-dominated northern ecosystems. Therefore, my research may document the initial stages of a widespread invasion in subpolar regions.
