Blumea 66, 2021: 57–81 www.ingentaconnect.com/content/nhn/blumea RESEARCH ARTICLE https://doi.org/10.3767/blumea.2021.66.01.03 Studies in Papuasian Syzygium (Myrtaceae): 2. The furfuraceous species of subg. Syzygium L.A. Craven1,†, K.Q. Damas2, K.J. Cowley1 Key words Abstract The furfuraceous species of Syzygium subg. Syzygium in Papuasia are revised. The scurfy, furfuraceous epidermis that is a feature of the inflorescence branches and sometimes also of the hypanthium, the commonly Furfuraceum chestnut brown colour of the dried leaves, and the reduced calyx that occurs in many species are characteristic identification key features of the group. Within this subgenus, a new section Furfuraceum is described to accommodate these maps morphologically recognisable species. Descriptions are provided for each of the 40 species recognised, 28 of which Myrtaceae are new. An identification key, distribution maps and an index to numbered exsiccatae are provided. Papuasia revision Syzygium Citation: Craven LA, Damas KQ, Cowley KJ. 2021. Studies in Papuasian Syzygium (Myrtaceae): 2. The furfuraceous species of subg. Syzygium. Blumea 66 (1): 57–81. https://doi.org/10.3767/blumea.2021.66.01.03. Effectively published online: 10 March 2021. INTRODUCTION leaves within the reproductive seasonal growth unit are very distinct in their size and form to those of the vegetative growth A concise background to recent research on the taxonomy units. A characteristic feature of the furfuraceous species is that of Syzygium P.Browne ex Gaertn. in Papuasia is given in the the leaves commonly dry a dark, chestnut brown and this is a first paper in this series (Craven 2019). An infrageneric classi- useful spot character in the herbarium. fication, an essential requirement in view of the size of the A furfuraceous, or scurfy, epidermis, shown in Fig. 1, is the genus, was proposed by Craven & Biffin (2010). Syzygium character that most defines the group. It usually occurs on the contains perhaps 1 200 to 1 500 species and subg. Syzygium branchlets of the inflorescence, persisting into the infructes- is the most speciose of the several subgenera, containing cence stage, and it also may occur on the hypanthium. In spe- perhaps 1 100 to 1 400 species, and in Papuasia this subgenus cies with a calyptrate calyx, such as S. megistophyllum Merr. & similarly is very speciose. In view of its size, the development L.M.Perry, the calyx also is furfuraceous. The vegetative of a classification of the subgenus should be a priority for future branchlets are rarely furfuraceous. The structure of the furfu- research in Syzygium. There are insufficient morphological raceous layer is of interest. The outer epidermis cracks, form- characters of diagnostic value to be able to propose even an ing small plates or scales (Fig. 1B1, C1), and these ultimately interim classification for the whole subgenus based upon this may fall, leaving a cellular, spongy-appearing tissue (Fig. 1B2, class of data; major DNA studies involving a large sampling C2). A function for this tissue is unknown. Given the apparent of species will be essential in developing an unambiguous geographic restriction of the furfuraceous species to Papuasia classification. With this caveat in mind, it is possible to suggest (with two of these species also extending to far north-eastern certain assemblages of species that very likely will be proven Australia and one to the Santa Cruz Islands), the correlation by DNA studies to represent natural groups, i.e., monophyletic of the furfuraceous epidermis with the frequent possession of clades. The present group, the furfuraceous species, is one dark brown leaves in the dried state, a reduced calyx, and a such assemblage. coherent and caducous corolla, the first author considers this Several morphological features warrant or require discussion. group of species represents a phylogenetically distinct clade The seasonal flush of growth that comprises or includes the that warrants taxonomic recognition. The new section Furfura­ inflorescence of a Syzygium plant may include leaves or be leaf- ceum is described below to accommodate this species group. less. This growth flush, termed ‘reproductive seasonal growth For convenience in making comparisons between species, unit’ for descriptive purposes, has a form that is characteristic separate descriptions are not given for inflorescences and and often very consistent for the various species. It often is leaf- infructescences; the structures being described under the less but may have leaves, typical of vegetative seasonal growth subheading ‘Inflorescence’. Although in the fruiting stage the units (i.e., growth flushes), in the proximal axils. Sometimes the branchlets are stouter than in the flowering stage, the overall size seems not to vary significantly between the flowering and 1 Australian National Herbarium, Centre for Australian National Biodiversity fruiting conditions. Research, GPO Box 1700, Canberra ACT 2601, Australia. The reduction of the calyx in the here newly described species 2 PNG Forest Research Institute, PO Box 314, Lae, Morobe Province, Papua New Guinea; corresponding author e-mail: S. hartleyi sp. nov., S. frodinii sp. nov., and other furfuraceous [email protected], [email protected]. species, is analogous with the reduction in, or even complete © 2021 Naturalis Biodiversity Center 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. 58 Blumea – Volume 66 / 1, 2021 1 2 1 a b 1 2 c d Fig. 1 Scanning Electron Micrographs: Furfuraceous inflorescence branch- lets in Syzygium. a–c. Syzygium furfuraceum Merr. & L.M.Perry: a. Branchlet showing strongly furfuraceous surface; b. close-up of epidermal layer: 1. outer epidermal flake; 2. spongy epidermal tissue; c. detail of epidermal layer: 1. outer epidermal flake; 2. spongy epidermal tissue. — d–e. Syzygium branderhorstii Lauterb. d. Branchlet showing weakly furfuraceous surface; e. close-up of epidermal layer (a–c: Takeuchi, Siga & Towati 14944; d–e: NGF (Vandenberg & Mann) 42251, all CANB). — Scale bars: a, d = 1 mm; e b, e = 100 μm; c = 10 μm. — Photos by Mark Talbot. loss of, the calyx that occurs occasionally in several other i.e., fused calyx and obsolete corolla, is the defining feature genera of Myrtaceae, e.g., Melaleuca L. (such as M. ciliosa of the generic concept Cleistocalyx Blume for which there is Turcz. and M. systena Craven) and Calytrix Labill. (such as C. no support with the species previously placed there nesting ecalycata Craven and C. paucicostata Craven). The inner pair across the genus in analyses based on DNA sequence data of calyx lobes is larger than the outer pair. The inequality in size (Craven et al. 2006). of the pairs of calyx lobes in Syzygium is common in species Application of the term ‘calyptra’ to Syzygium is problematic as with a 4-merous calyx but this is not an obvious feature of the there are three distinct structures to which the term is being 4-merous furfuraceous species as the calyx in these species applied, i.e., a fused caducous calyx (as in S. megistophyllum), is usually very poorly developed. In 5-merous species, the a fused caducous corolla (as in S. frodinii), and a coherent calyx lobes are of equal size. The coherent, caducous petals caducous corolla (as in S. bowersiae sp. nov.). It would en- are the major defining feature of the generic concept Syzygium able precise, unambiguous reference if each of these three s.str. Elsewhere in Myrtaceae, a similar petaline calyptra is structures had their own name but due to the small number also found in some species of Melaleuca, e.g., M. calyptroides of species across the genus that have one or other of the two Craven. Syzygium frodinii is unique within the genus for having fused structures (one species has a fused corolla and perhaps an obsolete calyx and a fused corolla. The reverse condition, around 50 species have a fused calyx) it is scarcely worthwhile. L.A. Craven et al.: Revision of Syzygium subg. Syzygium 59 Fig. 2 Staminal disc types in Syzygium species. Series 1: Flat; series 2: descending; series 3: ascending; series 4: raised. Consequently, the decision has been made to use the words grammatic form in Fig. 2 and the relevant diagrams indicated calyptra, calyptrate, etc., throughout the descriptive work but in the descriptions. specify the relevant form in each description. The conservation status of many of the species treated in this The staminal disc is the tissue upon which the stamens are in- revision is Data Deficient according to the criteria of the IUCN serted. The form of the staminal disc and associated tissues is Red List (IUCN 2012). Individual assignments of the several a valuable character state in the circumscription of species. The criteria are therefore not made to the species. Reference to the disc may be flat or variously ascending, descending or curved, distribution maps provides a ready approximation of the likely and there may be a ‘lip’ at its inner edge, all of which combine conservation status of the species and it can be seen that the to give a particular form to the disc and the adjacent tissues criterion of Least Concern most likely will apply to species such at the hypanthium apex.