Data from: 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 (1m2) 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.

热带安第斯高海拔区域拥有全球最为丰富的高山植物区系之一，特有种比例与物种更替率均处于极高水平。然而，学界对于调控植物群落多样性沿海拔与纬度梯度变化的格局与驱动机制仍知之甚少。本研究首次针对热带安第斯山地山顶的植物群落多样性开展了大陆尺度的比较研究。研究数据取自沿4200公里样带布设的50座山顶上的792个1平方米永久植被样方，各山顶海拔介于3220至5498米（m.a.s.l.）之间。本研究通过分析植物群落数据，开展三方面评估：（1）区域内各山顶的物种多度格局差异；（2）地理距离对植物区系相似性的解释贡献；（3）海拔与纬度环境梯度在塑造植物群落组成与物种丰富度中的重要性。基于物种多度格局，本研究中的山顶植物群落可划分为两大主要类群：普纳（Puna）与帕拉莫（Páramo）。植物区系相似性随研究样地间地理距离的增加而降低，且这一相关性在更为孤岛状的帕拉莫生境中强于普纳生境（对应帕拉莫内部更高的物种更替率）。排序分析（典范对应分析，Canonical Correspondence Analysis，CCA）结果显示，降水量、最高气温与岩石覆盖度是解释所有山顶群落相似性的最强预测因子。广义线性模型（Generalized Linear Model，GLM）准泊松回归分析结果表明，在所有山顶中，物种丰富度随最高气温与地上枯落物量的升高而增加，而在以岩屑坡为主要基质的山顶上，物种丰富度则有所降低。本研究结果表明，不同环境变量是解释安第斯高海拔山顶物种沿海拔与纬度更替格局及物种丰富度分布的核心因子，同时为探究热带安第斯区域气候变化在纬度与海拔梯度上的差异化影响提供了强有力的分析工具。