The Effect Of Climate Change On The Distributions Of Invasive Plants And Their Associated Biological Control Agents In North America
Authors:   , Curtis Caroline 
Published: February 2023

Climate change has the potential to alter the size, shape, and location of species’ distributions. As a result, the interactions between species are also likely to be impacted as novel species encounter each other and historical community assemblages are broken apart. To quantify the impact of distributional changes as a result of climate change on interacting species, distribution maps were produced for three species of invasive plant and their associated biological control agent at three time periods: current, 2050, and 2080. For each of the future time periods, two distribution maps were created for each species, representing the minimum and maximum emission scenarios considered. The area of the projected future distributions for each species was compared to the current distributions. Percent change in area of distribution was calculated to determine the effect of climate change on the distributions of individual species. The total area of overlap in the distribution of plants and their biological controls for each of the time periods and emission scenarios also was calculated and percent change from the current distribution was used to quantify the effect of climate change on the species interactions. The distributions of the invasive plant species do not follow a consistent trend across models. The distribution of St. Johnswort (Hypericum perforatum Linnaeus, 1753) is expected to increase by 2050, then decrease to an area smaller than the current distribution by 2080. Leafy spurge (Euphorbia esula Linnaeus, 1753) is predicted to have larger distributions by 2080 under both emission scenarios, although only the minimum emission scenario predicts an initial decrease from the current distribution to that expected for 2050. The distribution of yellow toadflax [Linaria vulgaris (Miller, 1768)] is expected to decrease under both emission scenarios by 2080. The distributions of two of the biological control agents (BCAs), Klamath weed beetle [Chrysolina quadrigemina (Suffrian, 1851)] and toadflax moth [Calophasia lunula (Hufnagel, 1766)], are expected to increase by 2080. For both future time periods and emission scenarios, the distribution of leafy spurge hawk moth [Hyles euphorbiae (Linnaeus, 1758)] is expected to decrease from its current area. The area of overlap between two pairs of species (St. Johnswort and the Klamath weed beetle; yellow toadflax and the toadflax moth) is predicted to increase over time. This indicates that the distributions of the invasive species and their associated BCAs will overlap to a greater extent than currently and the BCAs have the potential to remain viable control mechanisms. The area of overlap between leafy spurge and the leafy spurge hawk moth is expected to decrease over time, indicating that the distributions of the species are not likely to respond similarly to climate change. As a result, the leafy spurge hawk moth might not be a suitable control mechanism for leafy spurge in the future. Because of data limitations, the results of this work are applicable to basic understanding of the systems and species involved. However, similar work has the potential to lead to a better understanding of the impact of biotic interactions on invasive and non-native species. In smaller geographic extents, similar research could help prioritize management of invasion by identifying those species that are expected to have increased distributions and escape from their BCA as a result of future climate change.