Taxonomic studies of Glochidion (Phyllanthaceae) from the Indo-China Peninsula (II): The identities of G.anamiticum and G.annamense

Abstract The names Glochidionanamiticum (Kuntze) Kuntze ex Merrill and G.annamense Beille were previously reduced to synonyms of G.eriocarpum Champ. ex Benth. However, literature examination and morphological comparison suggest that G.annamense is conspecific with G.anamiticum and the species can be readily distinguished from G.eriocarpum by its styles connate into a long cylindric column and up to 3 mm long, ovaries usually 3-locular, stigma usually 3-lobed, capsules pubescent and usually 6-grooved, persistent styles 3‒4 mm long. Thus, the specific status of G.anamiticum is here reinstated and G. annamense is treated as its synonym.


Introduction
Glochidion J. R. Forster & G. Forster is a large genus within the tribe Phyllantheae Dumortier, family Phyllanthaceae Martinov (Webster 2014, APG 2016. It consists of over 300 species mainly distributed in the Indo-Pacific region, east to southeast Polynesia and south into Australia (Webster 2014, Yao andZhang 2016). The genus can be distinguished from all the other genera in the tribe by its usually unlobed styles, apiculate anthers and usually fleshy seed coat (Webster 2014).
Molecular phylogenetic studies revealed that Glochidion, together with Breynia J. R. Forster & G. Forster, Phyllanthodendron Hemsl. and Sauropus Blume, were all deeply embedded within Phyllanthus L. s. str. . So, some authors suggested the merger of these genera with Phyllanthus and accepted the broad concept of Phyllanthus s. l. (including Breynia, Glochidion, Phyllanthodendron and Sauropus) as a super-genus that includes over 1,200 species ). However, Pruesapan et al. (2012) suggested that the reinstatement of Breynia, Glochidion, Phyllanthodendron and Sauropus, as well as the disintegration of the paraphyletic Phyllanthus s. str. (over 800 species) into smaller genera, seems to be more reasonable, because these groups can be distinguished easily from each other in morphology and Phyllanthus s. str. is actually a large and morphologically heterogeneous genus with wide distribution areas. The latter suggestion is further supported by morphological (van Welzen et al. 2014), palynological (Yao and Zhang 2016) and wood anatomical (Jangid and Gupta 2016) studies. Thus, the acceptance of the generic status of Glochidion is widely adopted in most recent literature (e.g. van Welzen et al. 2014, Webster 2014, Duocet Group 2016onwards, Kato and Kawakita 2017. The species Glochidion anamiticum (Kuntze) Kuntze ex Merrill was originally described by Kuntze (1891) in the genus Diasperus L. ex Kuntze based on one collection (O. Kuntze 3798) from Vietnam and Glochidion annamense Beill was described by Beille (1927) based on five collections (F. Evrard 233, C. Gaudichaud 161, M. Krempf 1567, E. Poilane 7838 and E. Poilane 10022) from Vietnam, too. The latter was soon reduced to the synonymy of G. anamiticum (Merrill 1936). In the taxonomic study of the Thai Euphorbiaceae, Airy Shaw (1972) provisionally placed both names under G. eriocarpum Champ. ex Benth., expressing uncertainty by question marks and this questionable treatment was directly followed by van Welzen (2007) in Flora of Thailand. Subsequent taxonomists accepted Airy Shaw's proposal to treat G. anamiticum and G. annamense as synonyms of G. eriocarpum (Govaerts et al. 2000, Li and Gilbert 2008, The Plant List 2013onwards, Govaerts et al. 2018). However, G. annamense was recognised as a separate species by Nguyen (2007) when treating the Vietnamese Euphorbiaceae, but G. anamiticum was not considered. In our comprehensive taxonomic studies of Glochidion, we found that G. anamiticum and G. annamense represent the same species, but this species is clearly different from G. eriocarpum in morphology. We therefore propose to reinstate the specific status of G. anamiticum and treat G. annamense as a synonym of G. anamiticum.

Material and methods
Specimens of Glochidion deposited in the herbaria HN, IBSC, K, KUN, NY, P and PE were studied carefully in the present study and field investigations of G. anamiticum and G. eriocarpum were carried out in recent years. Morphological characters of relevant species were also photographed and some of them were measured. Herbarium abbreviations cited here follow the Index Herbariorum (Thiers 2018 onwards).
Distribution and habitat. Glochidion anamiticum is endemic to Vietnam, mostly from Da Nang to Ninh Thuan (Nguyen 2007).
Notes. In the monograph Revisio Generum Plantarum, Kuntze (1891) transferred hundreds of Glochidion and Phyllanthus species into the genus Diasperus L. ex Kuntze and he also described many new species, including Diasperus anamiticus Kuntze which was based on one of Kuntze's collections (O. Kuntze 3798) from Vietnam. At the same time, however, a specific name (Glochidion anamiticum), under the generic name Glochidion, was also suggested for D. anamiticus, but it was listed as a synonym of the new species. According to Art. 34.1 of the ICN (McNeill et al. 2012), the name G. anamiticum Kuntze is invalid because it was not accepted by the author and just cited as a synonym of Diasperus anamiticus. On the other hand, many of the new species described by Kuntze (1891) were overlooked for a long time, until they were re-evaluated by Merrill (1936) and then the species Glochidion anamiticum was accepted formally as a member of Glochidion for the first time. So, the author's attribution of the species should be Glochidion anamiticum (Kuntze) Kuntze ex Merrill. In his commentary on Loureiro's (1790) new species described from southern Vietnam, Merrill (1935) transferred the species Nymphanthus pilosus Lour. into Glochidion and reduced Glochidion annamense to a synonym of his new combination Glochidion pilosum (Lour.) Merr., although the type of G. pilosum was not examined in his study. Merrill's (1935) taxonomic treatment of Glochidion annamense was followed by Ho (2003) in An Illustrated Flora of Vietnam. However, as noted by Loureiro (1790) in the protologue of Nymphanthus pilosus, the species was characterised by pinnate leaves and bacciformis fruits, which are much different from those of the genus Glochidion (characterised by alternate and distichous leaves, fruits capsule), but consistent with those of Emblica Gaertn. or Phyllanthus sect. Emblica, thus the species also had been transferred into these two genera and named as Emblica pilosa (Lour.) Spreng. or Phyllanthus pilosus (Lour.) Müll. Arg., respectively. In the following year, however, Merrill (1936) treated the name Glochidion annamense as a synonym of G. anamiticum, based on the study of type specimens, but the name G. pilosum was not considered.  Cylindrical column, slightly exceeding the sepals, 1-1.5 mm long; Stigma Deeply 3(4)-lobed; Deeply 4-5-lobed; Ovary Pubescent; 3(4)-locular; Villous; 4-5-locular; Capsule Pubescent; 7-9 mm in diameter; deeply 6(8)-grooved; Villous; 8-10 mm in diameter; deeply 8-10-grooved; Persistent style Cylindrical column; up to 4 mm long; Shortly column-shaped to subconical; less than 1 mm long.