A review of the Chinese monotypic genus Melliodendron (Styracaceae), with a new synonym of M. xylocarpum
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ISSN: 0075-5974 (print) ISSN: 1874-933X (electronic)
A review of the Chinese monotypic genus Melliodendron (Styracaceae), with a new synonym of M. xylocarpum Xue-Hui Wu1, Rui Zhang1, Timothy M. A. Utteridge2, Yu-Lin Liu1, Guang-Yao Yang1 & Ming Tang1
Summary. Critical specimen examination and in vivo observations show that Melliodendron xylocarpum var. roseolum is morphologically no different from M. xylocarpum var. xylocarpum, with respect to purported diagnostic characters of twig shape and petal colour, as well as other fundamental characters, and should not be recognised as distinct and is here treated as a synonym of the nominate variety. A discussion of the morphological variation and geographical distribution of M. xylocarpum is given, as well as lectotypification of the synonyms. Key Words. China, Ericales, infraspecific taxa, lectotypification, morphology, taxonomy.
Introduction Melliodendron Hand.-Mazz., a monotypic genus first described by Handel-Mazzetti (1922) based on M. xylocarpum Hand.-Mazz., is a rare and beautiful endemic Chinese tree. The genus is a distinct member of Styracaceae, differing from other genera due to the combination of 1- or 2-flowered inflorescences, filaments of equal length and indehiscent and ribbed, but unwinged fruit elongating during development according to Hwang & Grimes (1996) and Fritsch et al. (2001). The relationships of the genus are still unresolved — in the most recent phylogeny of the family undertaken by Fritsch et al. (2001), a combined analysis using three molecular markers places Melliodendron in a clade either with Sinojackia Hu or Halesia carolina L., but these are poorly supported, as was the morphological analysis which placed Melliodendron in a clade with Parastyrax W.W.Sm., and Pterostyrax Siebold & Zucc. Melliodendron xylocarpum was described on the basis of two sheets of a single collection from Yaoshan (as Yiuschan), Shaoguan (as Siudsao = Schautschou), Guangdong (as Kwangtung) Province, namely R. E. Mell 37 (Fig. 1). Since its description the species has been widely accepted by many authors, including Hu (1934), Hu & Chien (1935), Handel-Mazzetti (1936), Chun (1940), Hwang (1980, 1987a, b), Hwang & Grimes (1996) and Fritsch et al. (2001). Melliodendron jifungense Hu (1963: 201) was described based on two sheets of a single collection from Huanggang Mountain (the highest peak in the Guan Mountains), Yifeng, Jiangxi Province, namely J. Xiong 4368 (Fig. 2A). In the protologue, Hu purported that it resembles M. xylocarpum in the leaf shape but differs by the smaller fruit. However, Hwang
(1980) treated M. jifungense as a synonym of M. xylocarpum, because she considered the fruit size of M. xylocarpum is variable and stated that the types of M. jifungense were collected with immature fruits. This was followed in the Flora of China treatment (Hwang & Grimes 1996). In the course of preparing a taxonomic revision of Styracaceae in China, Melliodendron xylocarpum var. roseolum Z.X.Yu, a taxon with the type collected from the Guan Mountains — the same location as
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