Taxonomic revision of the Onosma gaubae Sensu lato (Boraginaceae) based on morphological and ecological analysis

Abstract

Onosma is a genus with numerous taxonomical challenges, a wide range of morphologically similar species described only with uncertain and indistinct morphological characteristics and interspecific hybridization, so, there are many challenges, such as problems in identifying species as well as species delimitation. Therefore, a taxonomic revision of their descriptions seems to be necessary for solving the taxonomical ambiguities in the complex taxa. This study investigated the taxonomic relationships of O. gaubae and its allied species using morphological, micro-morphological and ecological approaches. Our results revealed that there is no significant difference in the qualitative and quantitative diagnostic characteristics (leaves, trichomes, stigmas, bracts, etc.) among the studied populations of O. gaubae s.l. The morphological variation along an ecological gradient of some populations of O. gaubae has caused taxonomic problems in the species and, so, these populations have been described as new species. O. borragoidinum and O. ghahremanii are suggested as synonyms of O. gaubae and a newly expanded description is given for this challenging group.