No Signal of Biotic Resistance to Non‐Native Species Establishment in High‐Elevation Communities
Meike Buhaly, Sophia Carmel Turner, Noemi Katalin Kreuz, Vigdis Vandvik, Benedikt Veltmann, Jake M. Alexander, Jonas J. Lembrechts, Ivan Nijs, Maria Alisa Alvarez, José Ramón Arévalo, Valeria Aschero, Joshua P. Averett, Agustina Barros, Pablo Castro Sánchez‐Bermejo, Lohengrin A. Cavieres, Vincent Ralph Clark, Curtis C. Daehler, Pervaiz A. Dar, Franz Essl, Georg V. Flückiger, Eduardo Fuentes‐Lillo, Casey Gibson, Christian Larson, Keith McDougall, Martin A. Nuñez, Aníbal Pauchard, Stephanie Payne, Tobias Proß, Petr Pyšek, Irfan Rashid, Amanda Ratier Backes, Zafar A. Reshi, Lisa J. Rew, Tim Seipel, Sandy‐Lynn Steenhuisen, Michaela Vítková, Genevieve Wright, Shengwei Zong, Sylvia HaiderABSTRACT
Questions
There is growing evidence of plant invasions in high‐elevation mountain ecosystems, but how these invasion patterns relate to native species diversity remains understudied. While the biotic resistance hypothesis states that highly diverse communities are less likely to be invaded than less diverse ones, the opposite pattern might arise from facilitative interactions in harsh environments, if these prevail at high elevations, especially in the alpine zone. Here, we investigate whether the relationship between native and non‐native plant species diversity changes with elevation, and whether it is modified by disturbance resulting from mountain roads.
Location
Global.
Methods
By using standardized vegetation surveys and plant trait measurements, we modeled the relationship between non‐native species richness and native species richness and functional diversity across elevation gradients, and whether they differ between (semi‐)natural habitats and adjacent disturbed roadside habitats.
Results
At high elevations, we recorded more non‐native species in functionally diverse natural habitats and in species‐rich roadside habitats. At lower elevations, non‐native and native species richness were positively associated, but fewer non‐native species established in functionally diverse natural habitats. Lateral spread of non‐native species from disturbed roadsides into natural habitats occurred with the same frequency at high and low elevations.
Conclusions
Our results suggest that once non‐native species reach high elevations along dispersal corridors such as roads, native plant diversity may help promote, rather than inhibit, their spread into natural plant communities, contradicting the biotic resistance hypothesis. While the positive correlation between non‐native and native species richness likely relies on beneficial environmental heterogeneity promoting both species groups, the seemingly inhibiting effect of native functional diversity at low elevations and its assumed supporting role at high elevations might reflect biotic processes such as limiting similarity and facilitation. This suggests that a complex interplay between native diversity and human disturbances shapes the invasibility of mountain ecosystems.