Thursday, June 25, 2020

[Botany • 2020] Rehderodendron microcarpum • Taxonomic Reassessment of Rehderodendron gongshanense (Styracaceae) based on Herbarium Specimens and Field Observations

Rehderodendron microcarpum K.M.Feng ex T.L.Ming 

in Zhao, Fritsch, Fan & Liao, 2020. 

Since its publication in 1988, Rehderodendron gongshanense (Styracaceae) has been considered endemic to Gongshan County, Yunnan Province, China and northern Myanmar. Based on morphological data from detailed field observations and examination of herbarium specimens, we demonstrate that R. gongshanense is actually a synonym of R. microcarpum, a species until now neglected taxonomically. We provide an updated description of Rmicrocarpum that accommodates the variation in the newly expanded concept of the species, along with comments on distribution and ecology, conservation status, specimens cited, and images of the living plants.

Keywords: Rehderodendron microcarpum, synonymy, taxonomy, Eudicots

Rehderodendron microcarpum.
Flowers opening before leaves expand, panicle densely stellate-tomentose.

Rehderodendron microcarpum K.M.Feng ex T.L.Ming (1983: 410). 
Type:—CHINA. Yunnan: Gongshan County, Dulong River, Dudu Village, open forest, ca. 1400 m, 14 September 1956, P.Y. Mao 451 (holotype KUN0026252!, isotypes KUN1293804!, KUN0026253!, KUN0026251!). 
= Rehderodendron gongshanense Y.C.Tang (1988: 350), syn. nov. 
Type:—CHINA. Yunnan: Gongshan County, Dulongjiang, Qinlangdang Village, in evergreen broad-leaved forest, ca. 1500 m, 11 August 1982, Exped. Qinghai-Xizang 9227 (holotype PE00027882!, isotypes KUN0774015!, KUN0774014!, PE00027880!, PE00028881!).

Distribution, ecology, and phenology:— Rehderodendron microcarpum has been documented as distributed in Gongshan, northwestern Yunnan Province in Southwest China, and Kachin State in northern Myanmar. It grows as a deciduous tree in montane monsoon forests at 500–2500 m a.s.l. It is known to flower in March and April, and fruit in June through October

Notes:— Some morphological characters of Rehderodendron microcarpum exhibit a high level of variation. The number of ribs varies from 5 to 12, and pubescence on the abaxial surface of the leaf blade varies from moderately dense to nearly glabrous. Floral characters, however, are relatively stable (panicles densely stellate-tomentose, style densely pubescent). The flowers of R. microcarpum are very similar to those of R. truongsonense P.W.Fritsch, W.B.Liao & W.Y.Zhao in Zhao et al. (2019: 159). These two species share such features as a pubescent style and filaments that are connate to the middle or distally beyond. However, R. microcarpum differs from R. truongsonense in its deciduous habit (versus evergreen), and longer inflorescence and pedicels. All other species of Rehderodendron have a glabrous style and filaments that are connate merely to just beyond the base. Therefore, R. microcarpum is easily distinguished from other species of Rehderodendron by the combination of its deciduous habit, a densely pubescent style, and filaments that are connate to the middle or distally beyond.

 Wan-Yi Zhao, Peter W. Fritsch, Qiang Fan and Wen-Bo Liao. 2020. Taxonomic Reassessment of Rehderodendron gongshanense (Styracaceae) based on Herbarium Specimens and Field Observations. Phytotaxa. 450(1); 1–7. DOI: 10.11646/phytotaxa.450.1.1