Thermal acclimation of tree species in a tropical Andean city: Exploring the role of species origin and thermal niche.

Premise: The warmer and drier atmospheric conditions of urban environments challenge plant performance to different extents based on a species' ability to acclimate to the conditions. We evaluated the influence of species origin and thermal niche on the acclimation of leaf traits and shifts in the occupation of the functional trait space of 10 tree species growing in two environmentally contrasting sites in Bogotá, Colombia.

Methods: We measured six leaf traits per species in both sites and used generalized linear models to evaluate the influence of origin and thermal niche on acclimation of leaf traits and t-tests to analyze shifts in the occupation of the functional trait space.

Results: Species origin predicted thermal tolerance and morphological trait acclimation to warmer conditions. Although exotic species decreased thermal tolerance at the warmer site, species from both origins acclimated traits consistently. Shifts in the occupation of the functional trait space varied between origins; warmer conditions reduced the size of the functional trait space of exotics and increased the phenotypic similarity of natives. Thermal tolerance acclimation and changes in functional trait space varied across species. Finally, thermal niche metrics were uncoupled from species origin and failed to explain the acclimation capacity of the studied species.

Conclusions: Although species origin influenced acclimation to warmer conditions, the effect of origin was not related to species' thermal niches. Our results provide crucial information for decision-makers involved in designing urban and peri-urban green spaces that can withstand climate change.