Dendrobium roseiodorum ( Orchidaceae ) : a new species from Vietnam

In the course of revisionary work of Dendrobium section Formosae, we found some misinterpretations of Dendrobium kontumense. Dendrobium schildhaueri is placed as a synonym of D. kontumense and D. roseiodorum, a new species from Vietnam, is described.


INTRODUCTION
Dendrobium Sw. sect.Formosae (Benth.& Hook.f.) Hook.f.(Orchidaceae), widely known by its synonymous name, sect.Nigrohirsutae (Lindl.)Schltr., comprises about 55 species and occurs from the Himalaya east to the Philippines and Sulawesi (Sathapattayanon, Yukawa & Seelanan, unpubl.).It is believed that sect.Formosae can be distinguished from the other Dendrobium sections by the presence of blackish hairs on leaf blades and leaf sheaths.However, several species from the Philippines and Borneo do not present this character.In fact, only the hard-textured flowers with white, greenish or yellow perianth lobes characterize the section (Yukawa 2004).A phylogenetic analysis of Dendrobium based on macromolecular data indicated the polyphyly of sect.Formosae (Wongsawad et al. 2005).These data suggest the necessity of re-examination of this section.
In the course of revisionary work of sect.Formosae, we have found misinterpretations of several species.Dendrobium kon tumense Gagnep. is one of such obscure entities and has been variously interpreted in previous taxonomic treatments.For example, Kerr (1969) and Seidenfaden (1973Seidenfaden ( , 1975) ) overlooked this species in their inventory works of Indochinese orchids.Subsequently, Seidenfaden (1985Seidenfaden ( , 1992) ) placed D. kontumense as a synonym of D. virgineum Rchb.f.On the other hand, Schildhauer (2002) and Ormerod & Pedersen (2003) rejected this view and applied the name D. kontumense to another plant.In this study, we review these treatments and clarify the status of D. kontumense.

SYSTEMATICS
In 1930, Poilane collected Dendrobium material from Kon Tum Province, Vietnam.Gagnepain (1932) recognized its new status and described it as D. kontumense.Kerr (1969) and Seidenfaden (1973Seidenfaden ( , 1975)), however, overlooked this species and identified Laotian materials assignable to this species as D. sculptum Rchb.f., a Bornean species, because both species are similar in having white flowers with an orange blotch on the lip and a narrowly conical mentum.Later, Seidenfaden (1985) recognized his misidentification and reduced it to a synonym of D. virgineum, a species described from Myanmar (Reichenbach 1884).
On the other hand, Schildhauer (2002) demonstrated differences between D. kontumense and D. virgineum from sketches of the type material and from the original descriptions.He thus concluded that D. kontumense was not a synonym of D. virgi neum but he misapplied the name D. kontumense to another entity, which is described here as a new species.Moreover, he did not recognize the differences between D. virgineum and the Indochinese material of D. virgineum sensu Seidenfaden.
Subsequently, Ormerod & Pedersen (2003) recognized the misinterpretation of D. virgineum by Schildhauer (2002) and described the Indochinese material of D. virgineum sensu Seidenfaden as a new species, D. schildhaueri Ormerod & H.A.Pedersen.As indicated by the history of interpretations of D. kontumense and D. virgineum, it is apparent that re-examinations of these species are needed.
First, we rechecked the holotype of D. virgineum (W) and found that it definitely belongs to D. infundibulum Lindl.complex (Sathapattayanon, Yukawa & Seelanan, unpubl.)and is not closely related to D. kontumense.We also found that the protologue and holotype of D. kontumense (Fig. 2e, f) completely agree with those of D. schildhaueri (Ormerod & Pedersen 2003).Vegetative parts of them are identical and they share floral features such as lanceolate-oblong sepals, elliptic petals, a narrowly conical mentum, a red central blotch on the glabrous lip and a transversely elliptic mid-lobe of the lip (Fig. 2c, d).From these evidences, we conclude that D. kontumense and D. schildhaueri represent the same taxon and that D. schildhau eri should be reduced to a synonym of D. kontumense.Furthermore, we examined the plant identified as D. kontu mense by Schildhauer (2002), Vestweber (2004) and Yukawa (2004) and compared it with the holotype of D. kontumense.We found that the flower of the former had densely verrucose calli on the lip, the golden yellow to orange side lobes and central part of a mid-lobe of the lip, a widely obovate mid-lobe narrower than side lobes of the lip, whereas the flower of the holotype of D. kontumense showed a glabrous lip, having only 3-5 slightly raised veins on the disc, a shape of mid-lobe more

Dendrobium roseiodorum (Orchidaceae): a new species from Vietnam
A. Sathapattayanon1,2 , T. Yukawa3 , T. Seelanan 1, 2   Abstract In the course of revisionary work of Dendrobium section Formosae, we found some misinterpretations of Dendrobium kontumense.Dendrobium schildhaueri is placed as a synonym of D. kontumense and D. roseiodorum, a new species from Vietnam, is described.

Key words
Dendrobium roseiodorum new species Orchidaceae Vietnam or less the same size as the side lobes of the lip.Moreover, an apical part of the lip of the former is more recurved and thicker than that of D. kontumense.We therefore recognized this plant as a new species, D. roseiodorum A.Sathapattayanon, T.Yukawa & T.Seelanan.
Dendrobium kontumense and the new species constitute a monophyletic group with D. draconis Rchb.f., D. ochraceum De Wild.and D. trankimianum T.Yukawa as demonstrated by a molecular phylogenetic analysis of Dendrobium sect.Formosae (Sathapattayanon, Yukawa & Seelanan, unpubl.).They share the following floral characters: a slender, narrowly conical mentum, a dilated base of the column and a raised margin of the column foot.The results of phylogenetic analyses further show that D. roseiodorum is most closely related to D. ochraceum.In fact, a synapomorphic morphological character, verrucose calli on the lip, also indicates their sister group relationship.However, several floral features of D. roseiodorum distinctly differ from D. ochraceum.The new species has a substantially golden yellow to orange lip (Fig. 2a), whereas D. ochraceum has a creamy yellow flower with scarlet veins on the lip (Fig. 2g).Further, they are distinguishable by the shape of the petals (elliptic-rhombic in D. roseiodorum; narrowly elliptic in D. ochraceum), the shape of side lobes of the lip (obliquely ovate in D. roseiodorum; obliquely elliptic in D. ochraceum, shown in Fig. 2h) and the verrucose calli of the lip (on the disc and veins in D. roseio dorum, shown in Fig. 2b; only on the veins in D. ochraceum, shown in Fig. 2h).Habitat & Ecology -Recorded on boulders or tree branches; 1000-1200 m altitude.Flowering: September to November (in natural habitat), July to December (in cultivation).

Dendrobium roseiodorum
Etymology -The specific epithet refers to the rose-like floral scent of the new species.