Chelsea Chisholm1, Tim Seipel2, Jörn Pagel3, Frank Schurr3, Jake Alexander1
1University of Lausanne, Lausanne, Switzerland, 2Montana State University, Bozeman, USA, 3University of Hohenheim, Stuttgart, Germany
Species invasions are a key driver of global change, but the dynamics of population spread remain poorly understood. As invasive species distributions are often in an expansion phase, it is difficult to model their potential distributions based on occurrence records alone, because their current distributions may not reflect their future range limits. Ideally, demographic data should be used to directly model spread dynamics and the formation of range limits. In order to tease apart the factors contributing to population spread and the formation of range limits, we used detailed time-series of occurrence and abundance data of the invasive plant Solidago canadensis across the Rhine river valleys in the Swiss Alps. We modelled range dynamics using a spatially-explicit dynamic occupancy model. This approach uses process-based models to estimate underlying population dynamics and demographic responses to environmental factors from species distribution and population-scale demographic data. Using additional herb-chronology data within populations, we were able to account for imperfect detection in data records, a common issue that is not addressed in classical species distribution modelling frameworks. We show that the upper range limits of this species are stable due to declining colonization with elevation, and there is evidence of a strong increase in abundance within its current range. Integrating information on demography and metapopulation dynamics is an important step forward in understanding the drivers of range dynamics of invasive species, and will improve our ability to reliably predict and mitigate future spread.
I am a postdoctoral researcher based at the University of Lausanne in Switzerland. I recently obtained my doctorate at the Center for Macroecology, Evolution and Climate in Copenhagen, where I focused my research on drivers of plant community change in mountainous regions. My current research continues in this vein, where I use data from both experiments and repeated surveys to address questions on how climate change is impacting alpine plant communities, and what implications this has for ecosystem functioning.