Blumea 57, 2012: 1–102 www.ingentaconnect.com/content/nhn/blumea RESEARCH ARTICLE http://dx.doi.org/10.3767/000651912X652012 A taxonomic revision of the Malesian species of Lasianthus (Rubiaceae) H. Zhu1, M.C. Roos2, C.E. Ridsdale2 Key words Abstract Based on herbarium collections, the Malesian species of the genus Lasianthus are revised. A total of 131 species including 5 subspecies and 6 varieties are recognized from the Malesian region, of which 41 species, Lasiantheae 3 subspecies and 3 varieties are described as new, and 3 new combinations are made for varieties. 22 species Lasianthus names and 15 variety names are reduced to synonyms. Ten species names and 2 varieties are treated as dubious Malesia mainly because their types cannot be traced. Additionally, 11 species are further excluded from Lasianthus. All revision species are described and a key to Malesian Lasianthus is given. Rubiaceae Published on 29 May 2012 INTRODUCTION 1938. Since 1950, many more specimens from the Malesian region have been collected, but a synopsis on the genus for Lasianthus Jack is a large genus of the Rubiaceae with more Malesia has not been made so far, except for two regional flora than 180 species, predominantly in the Old World. The great- treatments, i.e. Bakhuizen van den Brink (1965) for Java (treat- est species diversity is found in tropical Asia (Robbrecht 1988), ing 29 species including 2 provisional names) and Wong (1989) where some 160 species occur, only one extending into Aus- for the Peninsular Malaysia (dealing with 54 species including 8 tralia. The species of the genus occur almost exclusively in the unnamed ones). Therefore, the present revision of Lasianthus understory of primary forests, and have limited potential for from Malesia is most needed. Here we recognize 131 species physiological acclimation to high light levels (Cai et al. 2005). from the Malesian region, of which 41 species, 3 subspecies There are occasionally records from secondary or seriously and 3 varieties are described as new, and 3 new combinations disturbed forests or forest edges. Lasianthus species are usu- are made for varieties. 22 species names and 15 variety names ally present in large numbers in the tropical forests of Asia and are reduced to synonyms. 10 species names and 2 varieties may therefore represent an ecologically important element. are treated as dubious mainly because their types could not be The species of Lasianthus also show interesting distribution traced. Additionally, 11 species are excluded from Lasianthus. patterns, which are of special interest for the study of the bio- geography of tropical Asia and of prevailing speciation models in tropical rainforests. METHODS The tropical Asian representatives of the genus are regarded This paper is a classic taxonomic revision on the genus La­ to be extremely difficult taxonomically. The flowers and fruits sianthus for Malesian species based mainly on morphological are small and often shed from herbarium specimens. There are characters. The authors examined all collections from the only a few diagnostic characters available for delineating the Malesian region in AAU, BM, K, L, and U, and a selection of the species and the majority of the characters used are quantitative Malesian collections in the herbaria BKF, KEP, MO, and SING. features of the vegetative organs such as leaves, stipules, and Type specimens in C, E, HBG, NY, P, SING, US have also been bracts. It is therefore difficult to correctly determine a species checked. The species presentation is in alphabetical order. by referring to old descriptions only. In most herbaria that we The arrangement of synonyms is organized chronologically in visited, misidentifications of Lasianthus specimens were fre- homotypic paragraphs. All cited specimens are examined by quent. Quite some earlier species and even newly recognized the authors except a few type specimens which are indicated species have been described from a single type collection or as ‘n.v.’. a few collections only. Some types of Korthals’ species, which In total, all c. 3 600 specimens in K and L were examined. should be in Leiden, could not be traced, while others were Additional specimens from AAU received on loan were also destroyed in Berlin during the World War II. Even the holotype examined. More than 95 % of the Lasianthus collections in K of the type species of the genus L. cyanocarpus was destroyed and L have been identified for the present study. A small number by a fire in 1824 (Merrill 1952). of specimens, which do not belong to the species presently About 140 species names and numerous varieties were pub- recognized, could not be treated because of imperfect state lished based on Malesian collections (see below, Taxonomic (lacking complete flowers or fruits). All published names from History). All of these names except two were published before the Malesian region are covered in the present work. Nomen- clature and typification follow the International Code of Botanical 1 Xishuangbanna Tropical Botanical Garden, The Chinese Academy of Sciences, Kunming 650223, P.R. China; Nomenclature (McNeill et al. 2006). Lectotypifications for some corresponding author e-mail: [email protected]. of Blume’s species are made. Neotypifications are also made 2 Netherlands Centre for Biodiversity Naturalis (section NHN), Leiden Uni- for some species of which we could not trace type materials versity, P.O. Box 9514, 2300 RA Leiden, The Netherlands. and which are most probably lost. © 2012 Nationaal Herbarium Nederland You are free to share - to copy, distribute and transmit the work, under the following conditions: Attribution: You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). Non-commercial: You may not use this work for commercial purposes. No derivative works: You may not alter, transform, or build upon this work. For any reuse or distribution, you must make clear to others the license terms of this work, which can be found at http://creativecommons.org/licenses/by-nc-nd/3.0/legalcode. Any of the above conditions can be waived if you get permission from the copyright holder. Nothing in this license impairs or restricts the author’s moral rights. 2 Blumea – Volume 57 / 1, 2012 TAXONOMIC HISTORY Lasianthus as defined here has drupes or pyrenes with a thick wall. Species that show drupes with a thin wall (and do not Generic delimitation belong to Saprosma nor Amaracarpus), are here treated as Lasianthus Jack was established in 1823 based on two Su- dubious taxa. Their systematic position needs further study. matran species, Lasianthus cyanocarpus (later selected as Piesschaert (2001) studied the carpology of Psychotrieae and the type of the genus; see below) and Lasianthus attenuatus. gave a definition of Lasianthus as having a gynoecium with In the same year Blume (1823) listed several plant species 4–12 locules that develops into a drupe with 4–12 pyrenes. In under the genus name Mephitidia attributed to Reinwardt but our present treatment, we restrict Lasianthus to species with described one species M. hexandra himself. The genus was re- drupes with 2–9 mature pyrenes with a thick wall that develop described two years later by Reinwardt (1825), but no species from ovaries with 2–9 locules for the Asian representatives. were mentioned by him. According to the International Code Petit (1964) and Denys (1981) discussed that African species of Botanical Nomenclature (McNeill et al. 2006), the genus have pyrenes with a pre-formed oval to circular germination Mephitidia is attributed to Reinwardt ex Blume with M. hexandra lid that could easily removed. However, for Asian species, few Blume as type. Blume (1826–1827) realized that Mephitidia was studies of the germination lids of pyrenes have been carried out. synonymous with Lasianthus Jack and provided accounts of the Javanese species. Mephitidia continued to be used by some Delimitation of the species authors because they were aware of an earlier publication of The African taxa have to some extent been treated by Verdcourt Lasianthus Adans. (= Gordonia) for a genus in the Theaceae. (1976) for tropical East Africa. Denys (1981) revised the genus De Candolle (1830) was the most significant of these authors for Central Africa. There seems to be less work on the three and Korthals (1851) was the last author to use Mephitidia for the American species, however, Robbrecht (1982) commented upon Malesian species in taxonomic publications. Later, Lasianthus two of these on the occasion of a discussion of the synonymy Jack has been conserved for the genus treated here. of the Panamanian endemic genus Dressleriopsis. Blume (1823) described from Java a monotypic genus Lito­ Important for mainland SE Asia is the work of Hooker (1880) santhes, which is closely related to Lasianthus. Inherently who recognized some 52 species and placed them all in a sub- Ridley (1923a) reduced this genus to a section of Lasianthus, generic classification (see below, Infrageneric Classification). however Bakhuizen van den Brink (1965) retained Litosanthes Subsequently regional flora accounts were produced for former as a separate genus based on three characters: imbricate co- ‘Indo-Chine’ (Pitard 1924) and for Thailand (Craib 1934). Later rolla, forked stipules, and pedunculate inflorescences. Deb & Yamazaki (1964) revised the genus for the Ryukyu Islands Gangopadhyay (1991) transferred some Indian taxa to Litosan­ and Liu & Chao (1964) treated the Taiwanese species. Zhu thes, but subsequently Gangopadhyay & Chakrabarty (1992) (1994, 2002) treated the Chinese Lasianthus and then revised reduced these taxa of Litosanthes to a section of Lasianthus the genus for Thailand (Zhu 2001b). The taxa from the Indian (see section below). subcontinent have received considerable attention in recent The circumscription of Lasianthus Jack was more or less modi- years: Deb & Gangopadhyay (1989, 1991) for India and Rids- fied by later authors, especially referring to the number of ovary dale (1998) for Sri Lanka.