Volume 24: 203–232 ELOPEA Publication date: 19 May 2021 T dx.doi.org/10.7751/telopea14806 Journal of Plant Systematics plantnet.rbgsyd.nsw.gov.au/Telopea • escholarship.usyd.edu.au/journals/index.php/TEL • ISSN 0312-9764 (Print) • ISSN 2200-4025 (Online) A review of Dendrobium kingianum Bidwill ex Lindl. (Orchidaceae) with morphological and molecular- phylogenetic analyses Peter B. Adams1,2, Sheryl D. Lawson2, and Matthew A.M. Renner 3 1The University of Melbourne, School of BioSciences, Parkville 3010, Victoria 2National Herbarium of Victoria, Royal Botanic Gardens Victoria, Birdwood Ave., Melbourne 3004, Victoria 3National Herbarium of New South Wales, Royal Botanic Gardens and Domain Trust, Sydney 2000, New South Wales Author for correspondence: [email protected] Abstract Populations of Dendrobium kingianum Bidwill ex Lindl. from near Newcastle, New South Wales to southern and central west Queensland and encompassing all regions of the distribution were studied using field observations, morphometric analysis and nrITS sequences. A total of 281 individuals were used to construct regional descriptions of D. kingianum and 139 individuals were measured for 19 morphological characters, and similarities and differences among specimens summarised using multivariate statistical methods. Patterns of morphological variation within D. kingianum are consistent with a single variable species that expresses clinal variation, with short-growing plants in the south and taller plants in the northern part of the distribution. The nrITS gene tree suggests two subgroups within D. kingianum subsp. kingianum, one comprising northern, the other southern individuals, which may overlap in the vicinity of Dorrigo, New South Wales. The disjunct D. kingianum subsp. carnarvonense Peter B. Adams in central west Queensland, which can be distinguished by a predominately subterranean habit and a narrower labellum midlobe, was resolved sister to D. moorei F.Muell., which renders D. kingianum paraphyletic in the nrITS gene tree, but this position was not supported. Regional descriptions documenting clinal variation are provided. All previously described varieties, including D. kingianum var. pulcherrimum Rupp, are colour and growth forms of D. kingianum subsp. kingianum. Introduction Dendrobium kingianum Bidwill ex Lindl. (sect. Dendrocoryne) is a lithophyte found mainly on the eastern seaboard in the northern half of New South Wales (NSW) and southern Queensland. There are also isolated and disjunct populations in inland central west Queensland. Across this broad distribution the species is variable in plant form and floral colour. Dendrobium kingianum was discovered by European explorers in the 1830s when opening up agricultural land north of Newcastle, and was described in 1844 by John Lindley from material sent by John Carne Bidwell, and named for Bidwell’s friend Captain P.P. King of the Royal Navy. The collection location for type plants was not given but the description is consistent with those from the southern part of the range. Subsequently the known distribution was extended to the north as far as central Queensland. It has been widely cultivated in temperate zones. The species is of significant horticultural interest, and since the mid-20th century has been line bred and hybridised with other dendrobiums. There have been a number of taxa described, some separated at species level. This can create confusion for orchid hybrid registration. © 2021 Royal Botanic Gardens and Domain Trust 204 Telopea 24: 203–232, 2021 Adams, Lawson and Renner There are a small number of studies of chromosome counts (Adams 1992), pollination (Adams 1988, Adams and Lawson 1988) and fragrance biochemistry (Adams 1988, Adams and Lawson 1995). Molecular phylogeny reconstruction using nuclear ITS for the 12 species in sect. Dendrocoryne (Burke et al. 2008) resolved D. kingianum as sister to D. speciosum, a relationship also recovered using AFLP data by Simpson et al. (2018). The aims of this paper are to quantify variation within D. kingianum based on morphological and molecular phylogenetic analysis from populations across the distribution. In particular we are interested in morphological evidence relating to the potential existence of more than one species. Clements and Jones (2002) proposed that D. kingianum be split into three separate species under Thelychiton, namely, T. kingianus, T. pulcherrimus and T. carnarvonense. Neither Thelychiton nor these species have been accepted by the World Checklist of Selected Plant Families (WCSPF), Genera Orchidacearum Vol. 6 (Pridgeon et al. 2014) or a review of the systematics of Dendrobiinae (Adams 2011). We then formalise the results of this investigation, in conjunction with a taxonomic review of D. kingianum. Historical review of taxonomy Dendrobium kingianum is a variable species. In the late 19th and early 20th centuries, varietal status was proposed for particular plants with distinctive features, often flower colour and plant habit e.g. D. kingianum var. pallidum F.M.Bailey, D. kingianum var. silcockii F.M.Bailey, D. kingianum var. aldersoniae F.M.Bailey and D. kingianum var. album Williams. In 1943, Rupp described D. kingianum var. pulcherrimum Rupp for very short plants with comparatively large flowers from the upper Hastings River in the southern part of the range, and noted that few variations of the species were sufficiently constant to warrant even varietal rank. A description of the historical varieties and a subspecies are given below with comments. Dendrobium kingianum Bidwill ex Lindl. The protologue of D. kingianum (Lindley 1844) was based on a single cultivated plant shipped from Australia to England by J.C. Bidwill, purchased by the Loddiges brothers possibly in 1842 (Lindley 1845), and cultivated. The plant’s pseudobulbs were 4–5 inches long, bearing two leaves, and two-flowered inflorescences. D. (Desmotrichum) Kingianum; pseudobulbis ovatis in collum longum extensis apice bioliis, foliis ovalibus emarginatis, pedunculo terminali (2-floro foliis aequali ?), sepalis ovatis mento emarginato, petalis obovatis apiculatis duplo brevioribus, labelli trilobi pubescentis laciniis lateralibus acutis intermedia paulo longiore transverse rhombea angulis lateralibus rotundatis apiculi acuto axi elevata trilineata apice tridentata. This curious epiphyte was bought by the Messrs. Loddiges at the sale of Mr Bidwill’s New Holland Plants. It has pseudo-bulbs between four and five inches long, tapered from an ovate base into a very long and narrow neck, on the top of which stand two oblong emarginate dark-green rather wavy leaves. Between these is a flower-stalk having two pink flowers gaily spotted with crimson in the inside. It will probably flower more profusely when in better health, and will then be a plant of considerable interest. The following year Lindley (1845) published a longer treatment of the plant, including a colour illustration, and noted three flowered inflorescences and four-leaved canes. Mueller (1862) provided a description including the same characters as Lindley’s, but based on a specimen collected by Charles Stuart from the Severn River in New England, presumably from high altitude on the edge of the New England escarpment, where D. kingianum is common even today: Caulibus breviusculis pauciarticulatis basi sensim incrassatis, foliis 2-4 terminalibus ovato-lanceolatis, corymbo terminalia pauciflora, floribus roseo-purpureis, sepalis semilanceolato-ovatis petala ovato- lanceolata aequantibus, labello sepalis subaequilongo albo vittis purpureis striato trilobo, lobis lateralibus deltoideis, medio subreniformi apiculato integro, earinis tribus flavis usequ ad basin lobi medii extensis. In Nova Anglia haud procul a fluvio Severn. C. St. In indice orchidearum horti Schilleriani sequentes species Dendrobii Novo-Hollandicas nuperius enumerantur: D. calamiforme Lodd., D. lineolatum H.G.Rchb. (D. teres Lindl. nec R.Br.) Nondum vidi Dendrobium monoliforme (McLeay inedit), quod a viro reverendo R.L. King prope sinum Botany Bay in rupibus muscosis repertum et raritate minutie sicut caulibus subtiliter moniliformibus insigne dicitur. Hoc Forsan Bolbophyllis adscibendum est. Bentham’s description of D. kingianum in Flora Australiensis (1873: p. 280) encompassed more natural variation, with stems 3–6 inches tall, and 1–3 inflorescences per pseudobulb. He suggested Bidwill’s plant may have come from Moreton Bay, and cited specimens collected at ‘Biron’ (possibly Byron Bay) by Leichardt, and at New England collected by C. Stuart, so encompassing the elevational range occupied by the species: A review of Dendrobium kingianum Bidwill ex Lindl. (Orchidaceae) Telopea 24: 203–232, 2021 205 Stems usually 3 to 6 in. high, striate with prominent angles, thickened at the base. Leaves at the summit of the stem 3 to 5, lanceolate or oblong-lanceolate, acute, 3 to 4 in. long. Racemes within or above the leaves 1 to 3, longer than the leaves. Flowers of a reddish purple, on pedicels of 1/4 to 1/2 in. Bracts very small. Sepals broadly lanceolate, the lower ones much falcate, 4 lines long in some specimens, fully 5 in others. Petals about as long, but narrower. Spur conical, slightly incurved, about 3 lines long. Labellum not much shorter than the sepals, not undulate, the lateral lobes very prominent, almost oblong, obtuse, the middle lobe scarcely longer, but very broad, almost reniform, the disk with 3 raised lines or plates extending to the base of the middle lobe, but not beyond.—Bot. Mag. t. 4527; F. Muell Fragm. iii.