BACKGROUND The Mexican hand tree or Canac (Chiranthodendron pentadactylon) is a temperate tree species of cloud and pine-oak forests of southern Mexico and Guatemala. Its characteristic hand-shaped flower is used in folk medicine and has constituted the iconic symbol of the Sociedad Botánica de México since 1940. Here, the evolutionary history of this species was estimated through phylogeographic analyses of nuclear DNA sequences obtained through restriction site associated DNA sequencing and ecological niche modeling. Total genomic DNA was extracted from leaf samples obtained from a representative number (5 to 10 per sampling site) of individuals distributed along the species geographic range. In Mexico, population is comprised by spatially isolated individuals which may follow the trends of cloud forest fragmentation. By contrast, in Guatemala Chiranthodendron may constitute a canopy dominant species near the Acatenango volcano. The distributional range of this species encompasses geographic provinces separated by the Isthmus of Tehuantepec. The objectives of the study were to: (i) estimate its genetic structure to define whether the observed range disjunction exerted by the Isthmus of Tehuantepec translates into separate populations, (ii) link population divergence timing and demographic trends to historical climate change, and (iii) test hypotheses related to Pleistocene refugia. RESULTS Patterns of genetic diversity indicated high levels of genetic differentiation between populations separated by the Isthmus. The western and eastern population diverged approximately 0.873 Million years ago (Ma). Demographic analyses supported a simultaneous split from an ancestral population and rapid expansion from a small stock approximately 0.2 Ma corresponding to a glacial period. The populations have remained stable since the LIG (130 Kilo years ago (Ka)). Species distribution modelling (SDM) predicted a decrease in potential distribution in the Last Interglacial (LIG) and an increase during the Last Glacial Maximum (LGM) (22 Ka), Mid-Holocene (6 Ka) and present times. CONCLUSIONS Divergence time estimations support the hypothesis that populations represent Quaternary relict elements of a species with broader and northernmost distribution. Pleistocene climatic shifts exerted major influence on the distribution of populations allowing dispersion during episodes of suitable climatic conditions and structuring during the first interglacial with a time period length of 100 Kilo years (Kyr) and the vicariant influence of the Isthmus. Limited demographic expansion and population connectivity during the LGM supports the moist forest hypothesis model.

中文翻译：

---

温带树种Chianthodendron pentadactylon（锦葵科）的核系统地理学：中美洲云雾林中的第四纪遗迹。

背景技术墨西哥手树或Canac（Chianthodendron pentadactylon）是墨西哥南部和危地马拉的云和松橡树林的温带树种。其特征性的手形花用于民间医学，自1940年以来就已成为墨西哥社会银行的标志性标志。在这里，该物种的进化史是通过对通过限制位点相关的DNA测序获得的核DNA序列进行系统地理学分析来估算的和生态位建模。从叶样本中提取总基因组DNA，该叶样本是从沿物种地理范围分布的代表性个体（每个采样点5至10个）中获得的。在墨西哥，人口由空间上孤立的个体组成，这些个体可能会跟随云雾森林碎片化的趋势。相比之下，在危地马拉，Chianthodendron可能构成Acatenango火山附近的冠层优势种。该物种的分布范围包括由特万特佩克地峡隔开的地理省份。该研究的目的是：（i）估计其遗传结构，以定义由特万特佩克地峡施加的观测范围分离是否转化为单独的种群，（ii）将种群的发散时间和人口趋势与历史气候变化联系起来，以及（ iii）测试与更新世庇护有关的假设。结果遗传多样性模式表明，被地峡隔开的种群之间遗传分化程度很高。西部和东部人口之间的分歧大约为87.3万年前（马）。人口统计学分析表明，同时有祖先人口分裂和小规模种群快速扩张，对应冰川期约为0.2 Ma。自LIG（130年基洛（Ka）年前）以来，人口一直保持稳定。物种分布模型（SDM）预测末次冰期（LIG）的潜在分布减少，而末次冰期最大值（LGM）（22 Ka），中全新世（6 Ka）和当前时期则增加。结论发散时间估计支持以下假设：种群代表具有更广泛和最北端分布的物种的第四纪遗物元素。更新世的气候变化对种群的分布产生了重大影响，允许在合适的气候条件下散布，并在第一个冰期（长度为100 Kio年）内构造，并受到地峡的残暴影响。LGM期间有限的人口膨胀和人口连通性支持了潮湿的森林假设模型。