With the aim to explore how plants acclimate to elevation changes in the understudied (sub)alpine tropics we tested two hypotheses along a 1000-m elevation gradient in Mexico: (H1) due to a severe increase in abiotic constraints at higher elevations, the functional traits of the plant species will converge toward more resource conservation, and (H2) the specific growth forms and biogeographic origins present in the (sub)alpine tropics may influence the interspecific trait variation along the gradient. We measured five aboveground functional traits: specific leaf area (SLA), leaf dry-matter content (LDMC), leaf thickness, leaf area and plant height, of 11 species representing four growth forms: rosette, tussock grass, shrub and tree the soil microclimate. Microclimatic data revealed a steep decrease in soil water content at higher elevations. Across all species and all individuals, SLA, plant height and leaf area decreased with elevation, whereas LDMC and leaf thickness increased, all of which revealing adjustments towards resource conservation in line with H1. Consistently with H2, the functional traits of the growth forms that were characteristic of tropical alpine regions (tussock grasses and erect shrubs) were less sensitive to changes in elevation compared to more generalist growth forms such as forbs. In addition, within the growth form “rosette” the functional traits of species of tropical biogeographic origin changed with elevation, whereas those of Holarctic origin did not. Our data indicate a convergence of plant traits toward improved resource conservation at higher elevations, which may be influenced partially by the growth form and the biogeographical origin of plant species.

为了探索植物如何适应未充分研究的（亚）高山热带地区的海拔变化，我们沿着墨西哥 1000 米的海拔梯度测试了两个假设：（H1）由于高海拔地区非生物限制的严重增加，功能性植物植物物种的性状将趋向于更多的资源保护，并且（H2）（亚）高山热带地区存在的特定生长形式和生物地理起源可能会影响沿梯度的种间性状变异。我们测量了 11 个物种的五种地上功能性状：比叶面积 (SLA)、叶片干物质含量 (LDMC)、叶片厚度、叶面积和株高，这些物种代表四种生长形式：莲座丛、草丛草、灌木和树木以及土壤小气候。小气候数据显示，高海拔地区土壤含水量急剧下降。在所有物种和所有个体中，SLA、株高和叶面积随着海拔的升高而减小，而 LDMC 和叶厚度则增加，所有这些都揭示了与 H1 一致的资源保护调整。与 H2 一致，热带高山地区特有的生长形式（草丛草和直立灌木）的功能性状对海拔变化的敏感度与更普遍的生长形式（例如非草本植物）相比。此外，在“玫瑰花结”生长形式中，热带生物地理起源的物种的功能特征随着海拔的升高而变化，而全北极起源的物种则没有。我们的数据表明，植物性状趋于改善高海拔地区的资源保护，这可能部分受到植物物种的生长形式和生物地理起源的影响。