Studies on the Gesneriaceae in Laos II: <i>Lysionotus calcicola</i>, a new species from limestone karsts in north and central Laos, supported by morphological and molecular evidence

A new species of Gesneriaceae, Lysionotus calcicola Phonep., Soulad. &amp; Souvann., is described and illustrated based on morphological and molecular evidence. This species is distributed in limestone karsts in the Luangprabang, Vientiane and Khammouane provinces in northern and central Laos. The new species can be distinguished from the hitherto known species in the genus by its deciduous shrubby habit, up to 2 m tall, and oldest stems with 4‐rounded edges and longitudinal grooves, but young branches non‐grooved, which are considered to be an adaptation to the severe environment in limestone karst and cliffs. ML tree based on ITS showed that the new species form a well‐supported clade (94%), sister to the remaining Lysionotus species. Information on its distribution, ecology, phenology, vernacular name, and a provisional conservation assessment are provided.