Additions to the Flora of Bhutan: New National Records and Range Extensions of Primulaceae and Orchidaceae from Central and Eastern Bhutan

The Sino-Himalayan region is a speciation and diversity hotspot for montane flora, yet many remote alpine and temperate ecosystems remain under-explored. The current study adds significantly to the families Primulaceae and Orchidaceae to improve our knowledge of the floristic richness of Bhutan and its wider biogeographic relationships with neighboring floristic provinces. Floristic surveys were done along temperate and high-altitude gradients in Lhuentse, Trashiyangtse and central Bhutan from 2020 to 2026. The collected materials were morphologically analyzed in detail. Physical specimens were preserved and deposited at the National Herbarium of Bhutan (THIM). For remote or protected populations, virtual validation was conducted using non-invasive macro-photography against digitized global types and national biodiversity datasets. Spatial analysis and preliminary conservation assessments were performed using ArcGIS Pro and GeoCAT following IUCN guidelines. Primula dumicola W.W.Sm. (Primulaceae) and Habenaria lucida Wall. ex Lindl. (Orchidaceae) are reported as new national records for Bhutan. Habenaria lucida adds to the national orchid tally, taking it to 507 species. The morphological study of P. dumicola population in Lhuentse reveals homostyly, a specialized reproductive system for self-pollination. In addition, we report a significant global westward range extension of Liparis sootenzanensis Fukuy. from Southeast Asia and its subsequent eastward distribution record within the country. The alpine stoloniferous Primula flagellaris W.W. Sm. is also confirmed to have a major eastward range extension. These findings effectively bridge critical distribution gaps between the Eastern Himalayas and the Hengduan Mountains, reinforcing a convincing botanical affinity between the flora of Bhutan and southwest China.

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