Abstract
A new genus of Arundinarieae, Khoonmengia, is established to accommodate a unique new bamboo species, K. honbaensis, from central-southern Vietnam. The morphological features, habitats and distribution of Khoonmengia and related genera, i.e. Ampelocalamus and Hsuehochloa, are compared. The characters of its scrambling habit, internodes with brownish green dots, conspicuous nodes swollen at one side, elliptic buds wholly sunken into culm, extravaginal branching pattern, mid-culm branch complement with one central dominant branch elongating to reiterate the culm accompanied by several lateral slender branches, swollen culm sheath base with a distinctive zone of transverse wrinkles, synflorescence composed of only one spikelet, single or several to many synflorescences arranged into a raceme or panicle terminal on leafy branches, purple anthers and nut-like caryopsis with hardened pericarp and loosely adherent lemma and palea distinguish K. honbaensis from morphologically similar taxa. In order to investigate the phylogenetic position of this unknown bamboo, molecular phylogenetic analyses based on the nuclear gene GBSSI were also conducted, and the results proved that K. honbaensis is definitely a member of Arundinarieae with an isolated position, which also indicated that this species could not be assigned to any of the already described genera and supported the establishment of the new genus.
Highlights
Bamboos, including a single evolutionary radiation of 1,642 species in the grass family Poaceae, subfamily Bambusoideae, are important components in tropical to warm temperate forests (Vorontsova et al 2016)
Morphological analysis (Table 1) revealed that this unknown bamboo owns several unique vegetative and reproductive characters that are different from the two closely related genera, i.e. Ampelocalamus and Hsuehochloa, such as culm with brownish green dots (Figs 2F, 5A), swollen culm sheath base with a distinctive zone of transverse wrinkles (Fig. 5A), synflorescence composed of solitary spikelet, single (Figs 2J–K, 3B, 4H) or several to many synflorescences arranged into a raceme or panicle (Figs 3A, 4G) terminal on leafy flowering branches, and nut-like caryopsis with loosely adherent lemma and palea (Fig. 3J)
Our unknown bamboo species is different from Ampelocalamus in the extravaginal branching pattern, elliptic buds wholly sunken into culm (Fig. 6), and purple anthers
Summary
Bamboos, including a single evolutionary radiation of 1,642 species in the grass family Poaceae, subfamily Bambusoideae, are important components in tropical to warm temperate forests (Vorontsova et al 2016). The Arundinarieae are the temperate woody bamboos, a diverse clade of 31 genera and ca. In the nuclear gene phylogenies, this species formed a clade with the congeneric taxa (Yang et al 2013). These results implied that the nuclear genome and the plastid genome may have different evolutionary trajectories (Zhang et al 2012; Yang et al 2013). The most recent study based on phylogenetic analyses with RAD-seq data identified eight major lineages in Arundinarieae with strong support, which conflicts with earlier studies (Wang et al 2017)
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