Data from: Late Pleistocene origin of the entire circumarctic range of the arctic-alpine plant Kalmia procumbens

The circumarctic ranges of arctic-alpine plants are thought to have been established in the late Pliocene/early Pleistocene, when the modern arctic tundra was formed in response to climate cooling. Previous findings of range-wide genetic structure in arctic-alpine plants have been thought to support this hypothesis, but few studies have explicitly addressed the temporal framework of the genetic structure. Here, we estimated the demographic history of the genetic structure in the circumarctic Kalmia procumbens using sequences of multiple nuclear loci and examined whether its genetic structure reflects prolonged isolation throughout the Pleistocene. Both Bayesian clustering and phylogenetic analyses revealed genetic distinction between alpine and arctic regions, whereas detailed groupings were somewhat discordant between the analyses. By assuming a population grouping based on the phylogenetic analyses, which likely reflects a deeper intraspecific divergence, we conducted model-based analyses and demonstrated that the intraspecific genetic divergence in K. procumbens likely originated during the last glacial period. Thus, there is no need to postulate range separation throughout the Pleistocene to explain the current genetic structure in this species. This study demonstrates that range-wide genetic structure in arctic-alpine plants does not necessarily result from the late Pliocene/early Pleistocene origin of their circumarctic ranges, and emphasizes the importance of a temporal framework of the current genetic structure for understanding the biogeographic history of the arctic flora.

学界普遍认为，北极-高山植物（arctic-alpine plants）的环北极分布区形成于上新世晚期/更新世早期，彼时气候变冷造就了现代北极苔原（arctic tundra）。此前针对北极-高山植物全分布区遗传结构（range-wide genetic structure）的研究结果被认为支持这一假说，但鲜有研究明确阐释该遗传结构的时间框架（temporal framework）。本研究以环北极分布的平卧杜鹃（Kalmia procumbens）为研究对象，借助多个核基因座（nuclear loci）的序列数据，估算其遗传结构的种群历史（demographic history），并检验其遗传结构是否反映了更新世期间长期的种群隔离。贝叶斯聚类（Bayesian clustering）与系统发育分析（phylogenetic analyses）均揭示了高山与北极区域间的遗传分化，但两类分析得到的精细分组结果存在一定程度的冲突。本研究以更能反映深层种内分化（intraspecific divergence）的系统发育分析所得的种群分组为前提，开展基于模型的分析，结果显示平卧杜鹃的种内遗传分化大概率起源于末次冰期（last glacial period）。因此，无需假设该物种在整个更新世期间均存在分布区隔离（range separation），即可解释其当前的遗传结构。本研究表明，北极-高山植物的全分布区遗传结构未必源于其环北极分布区在上新世晚期/更新世早期的形成，并强调了解析当前遗传结构的时间框架，对于理解北极植物区系（arctic flora）的生物地理历史（biogeographic history）具有重要意义。