The Genus Dicksonia (Dicksoniaceae - Cyatheales) in Western Malesia
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Blumea 63, 2018: 268–278 www.ingentaconnect.com/content/nhn/blumea RESEARCH ARTICLE https://doi.org/10.3767/blumea.2018.63.03.02 The genus Dicksonia (Dicksoniaceae - Cyatheales) in western Malesia M. Lehnert1*, F.P. Coritico2 Key words Abstract We present an update of the taxonomy of the challenging genus Dicksonia in Malesia excluding New Guinea with its directly adjacent islands. The species D. blumei and D. mollis are maintained and additional distin- biogeography guishing characters are given. As here defined their ranges do not overlap, with D. blumei present on Sumatra, Java Indonesia and Bali, and D. mollis on Borneo and the Philippines. On Mindanao, D. mollis is sympatric with a newly recognized Mindanao species, D. amorosoana sp. nov. On Sulawesi, there is only one species confirmed, D. celebica sp. nov. All these New Guinea morphological separations are supported by molecular data. Also present in the area are D. timorensis, occurring Philippines only on Timor and more closely related to D. antarctica from southern Australia than to the rest of the Malesian Sulawesi taxa, and D. ceramica sp. nov., endemic to Seram Island and with strong affinity to the New Guinean D. lanigera taxonomy and D. hieronymi. Lectotypes are chosen for D. blumei and Balantium chrysotrichum. Descriptions and a key for tree ferns all species in the study area are provided. Published on 29 November 2018 INTRODUCTION we addressed the new species preliminarily as ‘D. cf. blumei’, because D. blumei (Kunze) T.Moore was the only other taxon Dicksonia is a well-known genus of tree ferns because it pro- known to occur within western Malesia. Given our incomplete vides the most commonly cultivated tree fern, D. antarctica knowledge at that time, we could not exclude the possibility that Labill. However, the taxonomy of the genus still contains many it represented just a local variety of that species. open questions. Most of the species are very similar to each In the meantime, the affinity of most of the taxa treated here other and their distinction is aided by their disjunct geographic has been tested phylogenetically (Noben et al. 2017). Among distributions. For example, D. antarctica, D. fibrosa Colenso and the Malesian species, the clear outlier is D. timorensis Adjie, D. sellowiana Hook. are superficially almost indistinguishable which is most closely related to D. antarctica from south-eastern and their distinction relies on seemingly feeble differences in Australia and Tasmania, among a clade in which most species segment shape and small hairs; yet their respective geographic are adapted to cooler and more seasonal climates than the rest restriction to Australia, New Zealand and South America has of the genus. All other Malesian samples are part of a differ- been the strongest argument for their separation. Extensive ent clade, in which most species belong to a relatively young field observations can add valuable distinguishing characters, like growth habit and ecological preferences, but these are radiation (Noben et al. 2017). Although with its soft hair being rarely supplied with the unavoidably fragmentary herbarium superficially more similar to the New Guinean D. lanigera Holt- specimens of tree ferns. Digital photographs have facilitated tum, the Philippine sample identified as ‘D. cf. blumei’ forms the documentation of the plants in the field and have greatly a separate subclade with samples from Sulawesi, which also aided the recent discovery of new species (Adjie et al. 2012, could just be identified to ‘D. cf. blumei’. This monophyletic Noben & Lehnert 2013), the first new descriptions for the genus ‘D. cf. blumei’ is characterized by a unique substitution pat- in almost fifty years. tern in the plastid genome (Noben et al. 2017, and references therein) that is found neither in D. mollis nor in D. blumei. The When FPC showed ML the field photographs of the plants he resolution in the crown group of the Malesian clade, which collected under the name Cibotium on Mindanao, it became consists of D. blumei and all New Guinean Dicksonia species, clear that the plant was actually a species of Dicksonia hither- is mostly weakly supported and needs further improvement to unrecognized in the Philippines. This species differs from before an evolutionary scenario between the island popula- the only documented Philippine species, D. mollis Holttum, in tions can be hypothesized (Noben et al. 2017). ‘Dicksonia cf. having only soft, woolly hairs on the fronds. Dicksonia mollis, blumei’ forms part of the well-supported paraphylum leading on the other hand, is characterized by stiff bristly hairs that up to it, sitting between the stiffly hairy D. herberti W.Hill and bear irritating tips on the petioles and major frond axes, mak- D. youngiae C.Moore ex Baker from Australia and D. mollis ing its handling very unpleasant. At that time, in the absence of better comparative material for a sound taxonomic decision, from the Philippines and Borneo (Noben et al. 2017). We find the documented molecular differences a compelling support for separating ‘D. cf. blumei’ from the already described species. 1 Nees-Institut für Biodiversität der Pflanzen, Rheinische-Friedrich-Wilhelms, There are considerable morphological differences between the Universität Bonn, Meckenheimer Allee 170, D-53115 Bonn, Germany; cur- rent address: Systematische Botanik und Mykologie, Ludwig-Maximilians- two known populations, which would make treating them under Universität München, Menzinger Straße 67, 80638 München, Germany; one name taxonomically unsound. Consequently, we describe corresponding author e-mail: [email protected]. them here as two species, D. amorosoana from the Philippines 2 Center for Biodiversity Research and Extension in Mindanao (CEBREM), (Mindanao) and D. celebica from Sulawesi. Central Mindanao University, Musuan, Bukidnon, The Philippines. © 2018 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. M. Lehnert & F.P. Coritico: Dicksonia in western Malesia 269 We further describe another species from Seram as new to sci- larger ence, D. ceramica, on morphological evidence alone. In order a flexuous, appearing to help further field studies, we provide amended descriptions evenly brown of D. blumei and D. mollis as well as a key to all Dicksonia hairs when thick, to species west of Lydekker’s line (Simpson 1977); i.e., to all of perispore Malesia except for New Guinea and its neighbouring islands. longer trends relatively all In this area, species are most easily determined by provenance applicable contorted clear (Map 1) but morphology is also reliable (Table 1). smooth, distributed n.a., not D. timorensis absent not not visible between longer hairs, whitish to pale brown yellowish brown medium brown, often crinkled when dried In the descriptions we adhere to the terminology of Lellinger show (2002), who applies the terms costa, costule and midvein dif- but ferently than Holttum (1963), who called them pinna rachis, costa and costule, respectively. We adopt the term ‘undercoat’ blackish stramineous retate of Holttum (1963) for a differentiated layer of usually shorter, to thick, hairs contorted softer hairs found on the petioles and thicker frond axes, through with impression, not which the more obvious longer hairs protrude. It is of diagnostic longer relatively % importance whether the longer hairs are stiff and spreading, all 25 thus exposing the undercoat, or if they are soft and curved so subjective ‘verrucose’, brown perispore atropurpureous c. D. ceramica absent flexuous, not visible between longer hairs, appearing pale reddish yellowish brown medium brown, often crinkled when dried that they obscure the undercoat. This pattern can change in and one species from the lower petiole to the thinner frond axes. To simplify discussion of the morphology, we also call the in- dusium shape ‘bivalved’ and distinguish an ‘inner’ and ‘outer’ variation longer n.a., valve, which anatomically are a true indusium and a modified retate hairs, to lobe of the laminar margin, respectively. Regarding the spore soft, brown natural with morphology, one type is dominating among the Malesian spe- to longer brown hairs cies, with the exospore weakly to strongly indented (‘areolate’ % contorted all reddish due to ‘foveate’ sensu Lellinger 2002), creating a network of blunt 75 ‘verrucose’, pale perispore medium atropurpureous c. absent ones not distinguishable between relatively thick, appearing yellowish brown medium brown, often D. amorosoana crinkled when dried anastomosing ridges (‘retate’ pattern sensu Lellinger 2002), on reliable which a fragile layer of perispore is deposited. The perispore consists of small granules that are usually fused to sticks of less short to moderate length (‘granulate’ to ‘baculate’ perispore are sensu Lellinger 2002). The other common spore type of Dick- retate flexuous n.a., sonia (in Malesia only found in two taxa) has the same type thick, parts to of perispore but in a continuous, even layer over a smooth with with plant exospore. As it is deposited last on the mature spore (Tryon brown of relatively % & Lugardon 1991), the perispore may vary in quality between 75 samples of viable spores. Sporangia of tree ferns seem to be atropurpureous c. perispore protruding from undercoat tips visible between bristly appearing pale reddish yellowish brown medium brown, often hairs, D.