The fate of páramo plant assemblages in the sky islands of the northern Andes.

Aims: Assessing climate change impacts on biodiversity is a main scientific challenge, especially in the tropics. We predicted the future of plant species and communities on the unique páramo sky islands by implementing the Spatial Explicit Species Assemblage Modelling framework. Specifically we: (a) calculated species' maximum dispersal distance; (b) modelled species' present and future distributions up to 2100; and (c) assembled models into plant communities. The final vulnerability assessment was based on a multi‐dimensional evaluation that considered the species, local plant community and sky island levels. Location: Ecuadorian super‐páramo (>4,200 m). Methods: Using species trait data, the maximum dispersal distance of 435 species was calculated. Species distribution models (SDM) were fitted to obtain current and future distribution predictions based on dispersal and bioclimatic factors. The final current assemblages and those for 2100 were achieved by stacking all probabilistic SDMs and applying the probability ranking rule. The vulnerability of each sky island was evaluated by quantifying richness and composition changes. Results: Maximum dispersal distances ranged between 0.008 m/year and 6,027 m/year, and across all scenarios, 70% of models showed a net loss in species distribution, while 9% of all species were predicted to undergo extinction in Ecuador by 2100. Local richness was estimated to decrease by 56.63% on average, and compositional changes in each sky island suggested a mean loss of 64.74% of their original species pool against a 12.97% gain. Finally, 5% of the sky island floras reconverted from high‐elevation to low‐elevation species. These numbers were usually more important for high‐elevation species and the mountains Pichincha, Ilinizas and Antisana. Conclusions: This methodological pioneer study provides novel insight into the future of páramo biodiversity. Significant losses in species distribution and changes in community richness and composition suggest drastic impacts and call for further research considering additional factors, such as land use. Finally, we recommend focusing monitoring and conservation strategies on the northern Ecuadorian sky islands as a priority. [ABSTRACT FROM AUTHOR]