Taxonomic Diversity of <i>Ranunculus</i> Section <i>Ranunculastrum</i> (Ranunculaceae) in Tajikistan, With an Identification Key and a New Species Based in Part on Molecular Phylogenetic Evidence

<i>Ranunculus</i> L. (Ranunculaceae) is a substantial genus of flowering plants with worldwide representatives and marked centers of diversity in mountainous systems. One area of heightened species diversity in the genus lies in the Central Asian Mountains. Here, the taxonomic diversity of <i>Ranunculus</i> (sect. <i>Ranunculastrum</i> DC.) from the mountainous Central Asian nation of Tajikistan is investigated and discussed, with new identification keys for all species of this group provided. A heretofore unknown population of a distinct lineage of <i>Ranunculus</i> was recorded on the Darwaz Ridge of Tajikistan and found to be an undescribed species. Revision of herbarium materials (authentic, general collection), fieldwork, and newly obtained phylogenetic data pertaining to this and other taxa from this group allowed the description and illustration of a new, narrowly endemic species of the Pamir-<i>Ranunculus boboevii</i>. An assessment of the conservation status, a geographical distribution map, habitat circumscription, and an illustration for <i>R. boboevii</i> are provided. Taxonomic relationships, morphological differences, phylogenetic position, and endemism of <i>Ranunculus</i> in the context of the flora of Tajikistan are also discussed.