Latitudinal and altitudinal patterns of plant community diversity on mountain summits across the tropical Andes

The high tropical Andes host one of the richest alpine floras of the world, with exceptionally high levels of endemism and turnover rates. Yet, little is known about the patterns and processes that structure altitudinal and latitudinal variation in plant community diversity. Herein we present the first continental-scale comparative study of plant community diversity on summits of the tropical Andes. Data were obtained from 792 permanent vegetation plots (1 m2) within 50 summits, distributed along a 4200 km transect; summit elevations ranged between 3220 and 5498 m a.s.l. We analyzed the plant community data to assess: 1) differences in species abundance patterns in summits across the region, 2) the role of geographic distance in explaining floristic similarity and 3) the importance of altitudinal and latitudinal environmental gradients in explaining plant community composition and richness. On the basis of species abundance patterns, our summit communities were separated into two major groups: Puna and Páramo. Floristic similarity declined with increasing geographic distance between study-sites, the correlation being stronger in the more insular Páramo than in the Puna (corresponding to higher species turnover rates within the Páramo). Ordination analysis (CCA) showed that precipitation, maximum temperature and rock cover were the strongest predictors of community similarity across all summits. Generalized linear model (GLM) quasi-Poisson regression indicated that across all summits species richness increased with maximum air temperature and above-ground necromass and decreased on summits where scree was the dominant substrate. Our results point to different environmental variables as key factors for explaining vertical and latitudinal species turnover and species richness patterns on high Andean summits, offering a powerful tool to detect contrasting latitudinal and altitudinal effects of climate change across the tropical Andes.Fil: Cuesta, Francisco. University of Amsterdam; Países BajosFil: Muriel, Priscilla. Pontificia Universidad Catolica del Ecuador; EcuadorFil: Llambí, Luis Daniel. Universidad de Los Andes; VenezuelaFil: Halloy, Stephan. Universidad Nacional de Chilecito; ArgentinaFil: Aguirre, Nikolay. Universidad Nacional de Loja; EcuadorFil: Beck, Stephan. Universidad Mayor de San Andrés; BoliviaFil: Carilla, Julieta. Universidad Nacional de Tucumán; Argentina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Meneses, Rosa Isela. Universidad Mayor de San Andrés; BoliviaFil: Cuello, Ana Soledad. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Grau, Alfredo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Gámez, Luis E.. Universidad de Los Andes; VenezuelaFil: Irazábal, Javier. Pontificia Universidad Catolica del Ecuador; EcuadorFil: Jácome, Jorge. Pontificia Universidad Javeriana; ColombiaFil: Jaramillo, Ricardo. Pontificia Universidad Catolica del Ecuador; EcuadorFil: Ramírez, Lirey. Universidad de Los Andes; VenezuelaFil: Samaniego, Natalia. Universidad Nacional de Loja; EcuadorFil: Suárez Duque, David. Giz; EcuadorFil: Thompson, Natali. Universidad Mayor de San Andrés; BoliviaFil: Tupayachi, Alfredo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Viñas, Paul. Naturaleza y Cultura Internacional; PerúFil: Yager, Karina. National Aeronautics and Space Administration. Goddart Institute for Space Studies; Estados UnidosFil: Becerra, María T.. Earth Innovation Institute; ColombiaFil: Pauli, Harald. Universitat Fur Bodenkultur Wien; AustriaFil: Gosling, William D.. University of Amsterdam; Países Bajo