After four exciting years with RangeX, I successfully defended my PhD at ETH Zürich at the end of March 2025. As the first PhD student to join the project back in 2021, I had the opportunity to witness and contribute to RangeX from its very beginning. From designing open-top chambers and figuring out how to transport 1800 seedlings up Calanda mountain, to learning how to model plant community temperatures using the ETH cluster, to an unforgettable field trip to South Africa and many great team meetings in beautiful locations, these years have been incredibly diverse, instructive, and rewarding.
In my PhD, I studied how plant species shift their ranges to higher elevations in response to environmental change—both through human mediated introductions and climate-driven expansions. I combined global vegetation survey data from the MIREN network with the output of the RangeX field experiment in Switzerland to explore these dynamics at different ecological scales. Using MIREN data from five continents, I showed that non-native plant species are increasingly spreading uphill. Species richness increased by about 16% over a decade, highlighting the growing impact of biological invasions in mountain ecosystems. In Switzerland, I found that most plant species (both native and non-native) shifted significantly upwards over 15 years, yet overall community temperatures barely changed, suggesting that communities lag behind climate change even more than individual species. To explore the reasons for species-level range shift lags, I used demographic data from our transplant experiment on Calanda mountain to estimate population growth rates of ten lowland species growing beyond their current range limits. Many were able to establish in the new climate but were held back by dispersal limitations and competition—highlighting the key role of non-climatic barriers in slowing range shifts. Together, these findings show that both non-native and native species are reshaping mountain ecosystems, and that understanding what limits species’ responses is crucial for predicting future biodiversity in a warming world.
I’m excited to see what other results will emerge from the project, and would like to thank my supervisor Jake Alexander and all the RangeX collaborators for four amazing years!
