Laboratório de Sistemática Vegetal, Departamento de Botânica, Universidade de São Paulo, São Paulo, SP 05508-090, Brazil.
Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
Proc Biol Sci. 2020 Mar 25;287(1923):20192933. doi: 10.1098/rspb.2019.2933. Epub 2020 Mar 18.
Mountains are among the most biodiverse areas on the globe. In young mountain ranges, exceptional plant species richness is often associated with recent and rapid radiations linked to the mountain uplift itself. In ancient mountains, however, orogeny vastly precedes the evolution of vascular plants, so species richness has been explained by species accumulation during long periods of low extinction rates. Here we evaluate these assumptions by analysing plant diversification dynamics in the , an ecosystem associated with pre-Cambrian mountaintops and highlands of eastern South America, areas where plant species richness and endemism are among the highest in the world. Analyses of 15 angiosperm clades show that radiations of endemics exhibit fastest rates of diversification during the last 5 Myr, a climatically unstable period. However, results from ancestral range estimations using different models disagree on the age of the earliest speciation events and point to a complex floristic assembly. There is a general trend for higher diversification rates associated with these areas, but endemism may also increase or reduce extinction rates, depending on the group. Montane habitats, regardless of their geological age, may lead to boosts in speciation rates by accelerating population isolation in archipelago-like systems, circumstances that can also result in higher extinction rates and fast species turnover, misleading the age estimates of endemic lineages.
山脉是全球生物多样性最丰富的地区之一。在年轻的山脉中，异常丰富的植物物种通常与山脉抬升本身有关的近期和快速辐射有关。然而，在古老的山脉中，造山运动远远早于维管植物的进化，因此物种丰富度可以通过在低灭绝率的长时间内的物种积累来解释。在这里，我们通过分析与前寒武纪山顶和南美洲东部高地相关的生态系统——的植物多样化动态来评估这些假设，这些地区的植物物种丰富度和特有性是世界上最高的。对 15 个被子植物类群的分析表明，特有种的辐射在过去 500 万年中表现出最快的多样化速度，这是一个气候不稳定的时期。然而，使用不同模型进行的祖先范围估计的结果在最早的物种形成事件的年龄上存在分歧，并指向一个复杂的植物区系组装。这些地区普遍存在更高的多样化率，但特有性也可能增加或降低灭绝率，具体取决于群体。山地生境，无论其地质年龄如何，都可能通过在群岛式系统中加速种群隔离来加速物种形成率，这种情况也可能导致更高的灭绝率和快速的物种更替，从而导致特有谱系的年龄估计出现偏差。
