基于系统发育的黄土高原地区木本植物多样性及特有性格局

Explaining the diversity and endemic patterns based on phylogenetic approach for woody plants of the Loess Plateau

黄土高原地区植被类型多样,森林、草原和荒漠在此交汇并逐渐过渡。由于水热条件限制和人类活动加剧,该地区生态环境脆弱,生物多样性保护面临的形势日益严峻,因此获取该区域物种多样性的空间分布格局并阐明其影响因素成为该地区生物多样性保护的首要任务。本研究首先结合标本采集记录与环境因子,利用物种分布模型获取了293种木本植物的潜在分布区,分析了物种丰富度和物种加权特有性的空间格局。其次,引入系统发育信息,分析系统发育多样性和系统发育特有性的空间格局,并进一步利用环境因子对上述格局分别进行解释。最后,对黄土高原地区的特有中心性质和显著性进行分析。结果表明,生物多样性热点地区均出现在黄土高原南部水热条件较好的地区,即秦岭和中条山一带。本区域的生物多样性空间格局由年平均降水量和最冷月最低温主导,符合植物区系交汇带的特点。特有中心集中在南部地区和青海省,由南向北分别是古特有中心和混合特有中心,不存在单独的新特有中心。黄土高原地区木本植物起源较为古老,生物多样性格局的形成以来源于热带或亚热带的物种扩散为主,物种的分化不占主导地位。上述结果表明了将植物的进化历史纳入生物多样性保护的重要性。

The Loess Plateau is home to various vegetation types as it contains famous transitional forests, grasslands, and deserts. Due to natural resource limitation and intensive human activities, this natural environment faces serious conservation challenges. In order to effectively conserve this natural environment, spatial mapping of species diversity is key to conservation efforts. In this study, we first modeled the potential distribution of 293 woody species based on specimen records and climate data and then calculated the spatial patterns of species richness and weighted endemism. Secondly, we calculated phylogenetic diversity and phylogenetic endemism and identified environmental drivers of the observed spatial patterns. Finally, we analyzed endemism types and tested their significance. Our results suggest that biodiversity hotspots are distributed on the southern edge of the Loess Plateau and are highly related to the flora of Qinling Mountains. The biodiversity patterns of this transitional region are driven by annual precipitation and minimum temperature of coldest month. Endemism hotspots were found on the southern edge of the Loess Plateau, which contain paleo-endemism and mixed-endemism, but no neo-endemism. We concluded that most woody species of the Loess Plateau originated in tropical or subtropical regions, and the species richness patterns of this region are maintained by dispersal rather than speciation. Our study indicated the importance of incorporating the evolutionary history in biodiversity conservation.