Revision of Anaphalis DC. (Asteracaeae: Gnaphalieae) in Nepal Himalaya

Abstract

Anaphalis is one of the 1620 genera of family Asteraceae and is placed in the tribe Gnaphalieae. Southwest China and Nepal are centres of diversity of the genus. It is the largest Asian genus of the tribe and includes c. 117 species in the world, mostly distributed in the Himalayas, North America and Southeast Asia. Although, there are a number of taxonomic treatments of genus in the regional floras, a comprehensive taxonomic account of the Nepalese Anaphalis is still lacking and there are taxonomic confusions among the currently defined species. The phylogenetic relationships of the genus are partially understood by a couple of previous studies, but sampling of major part of Nepalese species is still missing. This study provides a comprehensive knowledge on the diversity of Anaphalis in Nepal Himalaya, and it clarifies the phylogenetic relationships within the genus and its sister genera. To investigate the diversity of Anaphalis in Nepal Himalaya, the taxonomic entities of the genus were studied on the basis of their geographical and morphological discontinuity, and an explicit phylogenetic analysis was carried out based on morphology and nuclear ribosomal internal transcribed spacer (ITS) sequences. The results have suggested that Anaphalis as a genus is closely related to Helichrysum and Pseudognaphalium. The study has concluded that there are 18 species of Anaphalis in Nepal Himalaya, of which two species, A. chlamydophylla and A. rhododactyla, are new records. A. cinnamomea, which has been regarded as a synonym of A. margaritacea, has been reinstated as distinct species. Varieties, A. contorta var. flavescens, and A. triplinervis var. monocephala have been synonymized. Presence of A. alata, A. virgata, A. viridis and A. yunnanensis var. muliensis in Nepal Himalaya is regarded uncertain because of lack of authentic specimens. Morphological characteristics of cypselae of 17 species of the genus Anaphalis recorded from Nepal Himalaya were studied by using light microscope and Scanning Electron Microscope (SEM). Surface of cypselae of these species revealed significant taxonomic characteristics. On the basis of external surface of cypselae, species of Anaphalis can be broadly divided into two groups, one with epidermal surface, provided with twin hairs of varying length and abundance, and the other with epidermal surface with outward projecting papillae. The digital distribution maps generated from occurrence records indicate that A. adnata, A. araneosa, A. busua, A. cinnamomea, A. contorta, A. nepalensis, A. nubigena, A. tenella and A. triplinervis have wider distribution across Nepal Himalaya, whereas A. cavei, A. chlamydophylla, A. griffithii, A. rhododactyla, A. royleana, A. subumbellata, A. virens, A. xylorhiza and A. yunnanensis have relatively narrower distribution. Among all the species, A. rhododactyla needs more conservation efforts to redeem it from further loss. The study also shows that Anaphalis is an assemblage of closely related taxa, which have high degree of homoplasy. The molecular analyses using ITS (Internal Transcribed Spacers) sequences of nuclear DNA combined with morphological analyses reveal that there are some unresolved species within the genus, which require broader sampling to clearly define their status. In the strict consensus phylogenetic tree constructed from ITS sequences, Anaphalis splits into two major clades. Anaphalis adnata, A. cinnamomea and A. triplinervis constitute a well resolved first clade, but the clade itself is nested within Helychrysum, suggesting that they have uncertain status within Anaphalis. The second clade consists of the rest of the species in moderately to strongly supported subclades showing their close relationships.