New combinations in Decalobanthus (Convolvulaceae)
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ISSN: 0075-5974 (print) ISSN: 1874-933X (electronic)
New combinations in Decalobanthus (Convolvulaceae) Ana Rita G. Simões1,2,3 , Ponprom Pisuttimarn4, Pimwadee Pornpongrungrueng4 & Lars W. Chatrou3
Summary. The recent revisionary work of “Merremieae” has resulted in the segregation of the c. 100 species of the
pantropical genus Merremia into six genera. Thus, the formerly monotypic genus Decalobanthus was expanded, aggregating 13 species of Merremia s.l. The genus delimitation is coherent, with strong molecular phylogenetic and morphological support. Decalobanthus, hence, consists of woody climbers with broadly cordate leaves, large yellow or white flowers, four-valved chartaceous capsules, and is mostly distributed in Asia and the Pacific. Four species have remained classified in Merremia s.l., although molecular and morphological evidence unequivocally suggests their placement in Decalobanthus. In the present work, these are formally transferred to the genus, which now extends to 17 species.
Key Words. liana, Merremia, Merremieae, morning-glories, woody climbers.
Introduction Recent taxonomic rearrangements in tribe Merremieae (Convolvulaceae) have resulted in the dissolution of the pantropical genus Merremia sensu lato into six genera: Merremia Hallier f. (sensu stricto), Decalobanthus Ooststr., Camonea Raf., Distimake Raf., Xenostegia D.F.Austin & Staples and Operculina Silva Manso (Simões et al. 2015; Simões & Staples 2017). A considerable number of species are still placed in Merremia s.l. (Simões & Staples 2017), awaiting further phylogenetic, morphological and palynological studies to ascertain their generic placement. Decalobanthus, in particular, results from the expansion of a previously monotypic genus endemic to Sumatra (Indonesia), with the type species D. sumatranus Ooststr. This genus was initially described by Van Ooststroom (1936) for the presence of a small tubular corolla, the lobes of which are reflexed, with each lobe further parted into two. As the flowers of Convolvulaceae are pentamerous, this creates a particular “10-lobed” arrangement of the corolla fauce, that inspired the generic name Decalobanthus. As morphological and molecular studies recently brought to light that this species is nested within a clade of other woody climbers from SE Asia (Simões et al. 2015; Simões & Staples 2017), the generic delimitation was expanded, accommodating 12 additional species previously placed in Merremia s.l. The genus now comprises 13 species,
the monophyly of which is strongly supported in molecular phylogenetic analyses based on ITS and three plastid markers (Simões et al. 2015; Fig. 1). Decalobanthus is not characterised by unequivocal synapomorphies, viz. characters that uniquely evolved in this genus. However, species of Decalobanthus are robust woody climbers or lianas, for which they are very easily separated from the herbaceous or slender twining herbs of Merremia s.s. (Fig. 2). A combination of other morphological characters helps to differentiate them from closely related genera: leaves si
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