Biotic interactions with natural enemies do not affect potential range expansion of three invasive plants in response to climate change

Abstract

The ranges of species, including invasives, are expected to shift poleward in response to climate change. As their distributions expand, invasive species will encounter different communities and the resulting biotic interactions could affect invasive species range expansion dynamics. Here, we assess whether biotic interactions with natural enemies have the potential to affect range expansion dynamics of three invasive woody plants (Berberis thunbergii, Celastrus orbiculatus and Elaeagnus umbellata). To do so, we planted them in two sites in a region where they are currently abundant and in three sites in a northern region near their range edge where they are expected to become more common due to climate change. Two of the species have not yet been observed within any of the northern sites and one species is present within one of the northern sites. All species experienced more foliar herbivory in the higher latitude (northern) region and the two species that are currently absent from the northern sites experienced less foliar disease there. However, the regional differences in biotic interactions had very minor effects on survival; the only statistically significant reduction in survival was from foliar disease for B. thunbergii, and even that had only a marginal effect on survival. This suggests that, at least for these invasive species in this area, interactions with existing natural assemblages of natural enemies will have only an exceedingly minor effect on populations establishing near range edges.