Thursday, June 29, 2017

[Botany • 2017] Eutrema giganteum • A New Species (Brassicaceae) from Sichuan, southwest China


  Eutrema giganteum G.Q. Hao, Al-Shehbaz & J. Quan Liu 


Abstract
Eutrema giganteum (Brassicaceae), a new species from Hengduan Mountains in Sichuan Province, southwest China, is described, and its relationships to the closely related E. yunnanense is discussed based on morphological, cytological, and molecular data. It is similar morphologically to E. yunnanense but is readily distinguished by having robust (vs. slender), erect (vs. decumbent), and branched (vs. mostly simple), and rather tall stems (60–110 cm vs. 20–60 cm); curved (vs. straight), smooth (vs. torulose), and shorter fruit (5–8 mm vs. 8–15 mm); and fewer ovules per ovary (1–4 vs. 6–10). All examined individuals from different populations of E. giganteum clustered into a single clade sister to E. yunnanense in phylogenetic analyses using the combined nuclear ITS and plastid DNA datasets. Our cytological studies revealed that the chromosome number of E. giganteum is 2n = 44, with a genome size of 1160 (±8) Mb, while that of E. yunnanense is 2n = 28, with a genome size of 718 (±15) Mb. Multiple lines of evidence support the recognition of E. giganteum as a distinct species well differentiated from E. yunnanense.

Keywords: Brassicaceae, Cruciferae, Eutrema giganteum, new species, Eutrema yunnanense, molecular phylogeny


Figure 1. Eutrema giganteum G.Q. Hao, Al-Shehbaz & J. Quan Liu. sp. nov.
AB Habit C Leaves D Inflorescence E Flowers F Fruit.

Eutrema giganteum G.Q. Hao, Al-Shehbaz & J. Quan Liu, sp. nov.
巨型山嵛菜

Etymology: The specific epithet refers to the remarkably huge plant size. The erect stem can extend to around 60–110 (–140) cm, higher than all the other Eutrema species.

Distribution and habitat: Eutrema giganteum is currently known from Hengduan Mountains in western Sichuan, China, including Xiling Snow Mountain, Jiajin Mountain, Erlang Mountain, and Gongga Mountain (Fig. 2). It grows in shady, humid forests at elevation of 2200–2900 m.


 Guoqian Hao, Changbing Zhang, Ihsan A. Al-Shehbaz, Xinyi Guo, Hao Bi, Junyin Wang and Jianquan Liu. 2017.  Eutrema giganteum (Brassicaceae), A New Species from Sichuan, southwest China. PhytoKeys. 82: 15-26.  DOI:  10.3897/phytokeys.82.12329


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