Data from: Phylogeny and evolution of endemic species on Ulleungdo Island, Korea: the case of Fagus multinervis (Fagaceae)

The genus Fagus (beech, Fagaceae) consists of about 10 species discontinuously distributed in East Asia, eastern North America, and Europe. Fagus multinervis occurs only on Ulleungdo Island, Korea, and is an important component of the island's plant community. The species was described primarily based on one of its stem characteristics: it branches at the base, producing several primary trunks. In part because no extant Fagus species are found in mainland Korea, and because the closest populations of Fagus are found in Japan, F. multinervis has been considered to be derived from the Japanese species, F. japonica. However, a recent study synonymized F. multinervis under F. engleriana and proposed that the beech population of Ulleungdo Island was derived instead from China via long-distance dispersal. Fagus multinervis is morphologically very similar to F. engleriana, but it can be distinguished by having rhombic lenticels that are vertically elongated. We determined the nucleotide sequences of the trnK-matK, trnL-trnF, trnH-psbA, and atpB-rbcL regions of plastid DNA and the second intron of the nuclear LEAFY gene from accessions of eight species, including eight F. multinervis individuals, in order to clarify the phylogenetic placement of this insular species. Phylogenetic analyses show that F. multinervis is monophyletic, and that it is closely related to F. engleriana and F. japonica. However, a sister relationship of F. multinervis with either of those species is not resolved. Therefore, our molecular data support the distinctness of F. multinervis as an endemic on Ulleungdo Island. Furthermore, incongruence between plastid and nuclear data suggests that F. multinervis may have originated via hybridization.山毛榉属（Fagus，壳斗科Fagaceae）约含10个物种，间断分布于东亚、北美东部及欧洲。多脉山毛榉（Fagus multinervis）仅分布于韩国郁陵岛，是该岛植物群落的重要组成成分。该物种最初主要依据其茎部的一项特征被命名发表：其基部具分枝，可形成数个主干。由于朝鲜半岛大陆地区并无现存山毛榉属物种分布，且最近的山毛榉属种群见于日本，多脉山毛榉曾被认为起源于日本山毛榉（Fagus japonica）。但近期有研究将多脉山毛榉归为恩格勒山毛榉（Fagus engleriana）的异名，并提出郁陵岛的山毛榉种群实际是通过长距离扩散从中国起源的。多脉山毛榉在形态上与恩格勒山毛榉极为相似，但可通过其具纵向伸长的菱形皮孔加以区分。为明确这一岛屿特有种的系统发育位置，本研究对8个山毛榉属物种的质体DNA（plastid DNA）的trnK-matK、trnL-trnF、trnH-psbA及atpB-rbcL区段，以及核基因组LEAFY基因的第二内含子进行了核苷酸序列测定，样本共包含8株多脉山毛榉个体。系统发育分析结果显示，多脉山毛榉为单系群，且与恩格勒山毛榉和日本山毛榉亲缘关系密切。但多脉山毛榉与上述任一物种的姐妹群关系尚未得到明确解析。因此，本研究的分子数据支持多脉山毛榉作为郁陵岛特有种的独立分类地位。此外，质体基因组与核基因组的数据存在不一致性，这表明多脉山毛榉可能起源于杂交事件。