A nomenclatural and taxonomic re-evaluation of neglected Centaurea candelabrum Hayek & Kosanin (sect. Acrocentron, Asteraceae) and related serpentine endemics from the Balkan Peninsula

Abstract

Centaurea sect. Acrocentron comprises several taxonomically intricate groups of taxa, including the Balkan endemic obligate serpentinophytes: C. melanocephala, C. candelabrum and C. albertii. Despite its distinctive morphological characteristics, C. candelabrum was considered conspecific with C. melanocephala. A similar situation pertains to C. albertii, which has largely been considered a synonym of C. melanocephala. Considering that several recent floristic works treat these taxa as separate species distributed in different serpentinite areas of the Balkans, the main objectives of our study were to analyse the taxonomic and chorological relationships between them, and to propose a new taxonomic concept. Our study was based on an extensive revision of herbarium material, including the type specimens, personal field data and observations of living plants. Our comprehensive study showed that the plants previously recognised as C. melanocephala from the Stolovi mountain in central Serbia and those previously recognised as C. candelabrum from northern Albania deserve the rank of distinct species. These species can be easily distinguished from each other by a number of characters, including their general habitus, the dimensions and shape of the basal leaves, and the indumentum of the involucral bracts. Given the only slight differences observed between the populations in Kosovo and Albania, the question of whether C. albertii is conspecific with C. candelabrum or deserves an independent taxonomic status remains unresolved until further detailed integrative studies are conducted. In view of the clear differences in morphological and ecological characteristics which exist within this group compared to other representatives of sect. Acrocentron, we propose the separation of the studied taxa into a separate C. melanocephala complex, as outlined in this paper.