Thermal niche traits of high alpine plant species and communities across the tropical Andes and their vulnerability to global warming

Francisco Cuesta,Luis D Llambí,Harald Pauli,Paul Viñas,Karina Yager,Stephan Beck,Priscilla Muriel,Wouter Buytaert,William D Gosling,Julieta Carilla,Carolina Tovar,Carmen Ulloa Ulloa,David Suárez‐Duque,Stephan Halloy,Jorge Jácome,Nikolay Aguirre,Rosa I Meneses

doi:10.1111/jbi.13759

Abstract

AbstractAimThe climate variability hypothesis (CVH) predicts that locations with reduced seasonal temperature variation select for species with narrower thermal ranges. Here we (a) test the CVH by assessing the effect of latitude and elevation on the thermal ranges of Andean vascular plant species and communities, and (b) assess tropical alpine plants vulnerability to warming based on their thermal traits.LocationHigh tropical Andes.TaxonVascular plants.MethodsTemperature data for 505 vascular plant species from alpine communities on 49 summits, were extracted from 29,627 georeferenced occurrences. Species thermal niche traits (TNTs) were estimated using bootstrapping for: minimum temperature, optimum (mean) temperature and breadth (maximum‐minimum). Plant community‐weighted scores were estimated using the TNTs of their constituent species. CVH was tested for species, biogeographical species groups and communities. Vulnerability to global warming was assessed for species, biogeographical species groups and communities.ResultsSpecies restricted to the equator showed narrower thermal niche breadth than species whose ranges stretch far from the equator, however, no difference in niche breadth was found across summits’ elevation. Biogeographical species groups distributed close to the equator and restricted to alpine regions showed narrower niche breadth than those with broader ranges. Community‐weighted scores of thermal niche breadth were positively related to distance from equator but not to elevation. Based on their TNTs, species restricted to equatorial latitudes and plant communities dominated by these species were identified as the most vulnerable to the projected 1.5°C warming, due to a potentially higher risk of losing thermal niche space.Main conclusionsOur study confirms that the CVH applies to high tropical Andean plant species and communities, where latitude has a strong effect on the thermal niche breadth. TNTs are identified as suitable indicators of species’ vulnerability to warming and are suggested to be included in long‐term biodiversity monitoring in the Andes.

Highlights

Some of the first evidence for a close relationship between tempera‐ ture and vegetation was provided by Alexander von Humboldt whilst travelling in tropical America in the early 19th century (Romanowski & Jackson, 2009)
Based on the GLORIA‐Andes datasets that contain vascular plant species data from mountain summits distributed from Venezuela to northwest Argentina, plus plant distribution data extending beyond this area, the aims of this paper were (a) to test the climate variability hypothesis (CVH) on the re‐ lationship between temperature seasonality and the observed ther‐ mal traits of tropical alpine species and communities along (1) latitudinal and (2) elevation gra‐ dients and (b) to assess the vulnerability of plant species to climate warming based on their observed thermal niche traits
The majority of the species belonging to the Páramo endemic, Tropical Andean alpine and Puna endemic biogeographical groups had a lower thermal optimum and narrow thermal niche breadth, suggesting higher susceptibility to climate warming (Figure 5a, Table S3 in Appendix S1)

Summary

| INTRODUCTION

Some of the first evidence for a close relationship between tempera‐ ture and vegetation was provided by Alexander von Humboldt whilst travelling in tropical America in the early 19th century (Romanowski & Jackson, 2009). Among the few exceptions are a study that re‐visited sites surveyed by Humboldt over 200 years ago (Morueta‐Holme et al, 2015), and a comparison of Andean forest plots that had been censused on multiple occasions since the 1990s (Fadrique et al, 2018) Both studies found evidence of directional upward shifts in community composition related to warming. Based on the GLORIA‐Andes datasets that contain vascular plant species data from mountain summits distributed from Venezuela to northwest Argentina, plus plant distribution data extending beyond this area, the aims of this paper were (a) to test the CVH on the re‐ lationship between temperature seasonality and the observed ther‐ mal traits (thermal niche breadth, optima, minima) of tropical alpine species and communities along (1) latitudinal and (2) elevation gra‐ dients and (b) to assess the vulnerability of plant species to climate warming based on their observed thermal niche traits. We assessed the potential vulnerability of species and communities to climate warming using the estimated proportion of species niche breadth contraction under a moderate climate change scenario by the end of the century

| MATERIALS AND METHODS

Findings

| DISCUSSION