Shiotani Yuki, Fukuda Tomoko, Marchuk Elena A, Petrunenko Ekaterina A, Krestov Pavel V, Bondarchuk Svetlana N, Nishikawa Yoko, Shimamura Takashi, Fujimura Yoshiyasu, Nakamura Koh
Division of Biosphere Science, Graduate School of Environment Science, Hokkaido University, Sapporo 060-0810, Japan.
College of Liberal Arts and Sciences, Mie University, Tsu 514-8507, Japan.
PhytoKeys. 2020 Dec 23;170:83-91. doi: 10.3897/phytokeys.170.58585. eCollection 2020.
It has been controversial whether , a dwarf birch distributed in Hokkaido of northern Japan, is an endemic species or a synonym of broadly distributed in northeast Asia. The endemic hypothesis is based on the idea that is diploid while is tetraploid and that they are separated based on the ploidy level; however, no chromosome data have actually been published before. Resolving the taxonomic problem is crucial also in judging the conservation priority of in a global perspective. Our chromosome observation revealed that is tetraploid as well as . We also conducted morphological observations and clarified that is morphologically identical to in white hairs and dense resinous glands respectively on adaxial and abaxial leaf surfaces, in which they differ from closely related species in the same section Fruticosae. We conclude that the hypothesis that is a Hokkaido endemic based on the ploidy level is not supported and that should be merged with .
分布于日本北部北海道的矮桦（Betula nana）究竟是一个特有物种，还是广泛分布于东北亚的矮桦（Betula exilis）的异名，一直存在争议。特有物种假说基于这样的观点，即矮桦（Betula nana）是二倍体，而矮桦（Betula exilis）是四倍体，它们基于倍性水平而分离；然而，此前实际上并没有发表过染色体数据。从全球角度判断矮桦（Betula nana）的保护优先级时，解决分类学问题也至关重要。我们的染色体观察表明，矮桦（Betula nana）和矮桦（Betula exilis）一样也是四倍体。我们还进行了形态学观察，并明确了矮桦（Betula nana）在叶片正面的白色绒毛和背面密集的树脂腺方面，在形态上与矮桦（Betula exilis）相同，而在这些特征上它们与同一组（Fruticosae）中的近缘物种不同。我们得出结论，基于倍性水平认为矮桦（Betula nana）是北海道特有的假说不成立，矮桦（Betula nana）应与矮桦（Betula exilis）合并。
