Abstract

Global change is catalyzing range shifts, yielding novel community assemblages as the leading edge of expanding species interact with the lagging edge of resident communities. It remains unclear how the effects of both novel biotic interactions, created by these newly overlapping ranges, and global change drivers interact to regulate the range expansion of incoming species. Here, we tested how novel biotic interactions and global change drivers jointly determine demography of a subalpine globeflower expanding its range into alpine moist-meadow communities, at Niwot ridge, CO.  Leveraging a 17-year experiment with global change manipulations of day-time warming, increased snowpack, and their interaction, we experimentally simulated the range expansion of Trollius albiflorus by transplanting adults into alpine communities that have adjusted to their global change treatment, and tracked their demographic rates from 2021-2024. Generally, the sign of below-ground biotic interactions was regulated by global change drivers (competitive versus facilitative), whereas the magnitude of below-ground biotic interactions on Trollius survival was regulated by above-ground density, and the growth-habit of the alpine neighborhoods (forb versus graminoid). Our results emphasize that the multifacetted aspects of novel biotic interactions on range expansions may be predictable, moderated by how the resident, lagging communities experience global change as stressors or releases from limiting resources. 

Speaker Bio

Megan is a community ecologist interested in how fundamental processes of species interactions, environmental change and dispersal, interact to affect species demography, especially in a global change context.  She is currently a postdoc at Case Western Reserve University, working with Dr. Karen Abbott. She received her doctorate from the University of Wyoming in 2025.