TAXONOMIC AND CONSERVATION STUDIES OF THE ARABIAN PENINSULA VERBASCUM SPECIES

Abstract

Verbascum L. (Scrophularieae, Scrophulariaceae) is a genus of approximately 360 species, which are classified into two recognised sections based on seed morphology, namely Bothrospermae and Aulacospermae. The greatest diversity of Verbascum species is found in Western Asia in the Bothrospermae section. In contrast, species belonging to the Aulacospermae section are found mainly in tropical Africa and the Arabian Peninsula. Verbascum species are widely recognised for their socioeconomic value as ornamentals and traditional medicines. This genus, which includes species from the Arabian Peninsula, has a long and complicated taxonomic history due to the extreme similarity and hybridization among its species, which led to several incorrect identifications. Thus, this thesis aims to systematically review the Verbascum genus in the Arabian Peninsula and evaluate the conservation status of its species through taxonomic revision with morphological examinations, phylogenetic analysis, Red List assessment for each taxon, and in situ and ex situ gap analysis and conservation planning. The taxonomic revision recognises 16 Verbascum species in the Arabian Peninsula, including newly described and recorded species. It also provides valuable details for identifying and delimiting these species, a species identification key, typified names, new synonyms and combinations, comprehensive descriptions of each species, and ecological and geographical distribution details. The results of the phylogenetic analysis confirmed the monophyly of the genus Verbascum and revealed the phylogenetic relationship and species delimitation within the genus in the study area. In addition, 236 novel DNA sequences representing 16 species with four varieties of this genus were provided to the GenBank database. The phylogenetic analysis also strongly supports the reinstatement of the genus Rhabdotosperma into Verbascum. The Red List assessment results indicated that most of the Arabian Verbascum taxa are threatened with extinction; four taxa are critically endangered and four are endangered. In addition, five taxa are assessed as near threatened, and five are assessed as of least concern. The Red List assessment results identified that the main threats to these taxa are habitat disturbance and loss resulting from overgrazing, suburban and agricultural expansion, climatic changes, invasive species, recreational activities and tourism, and war and civil unrest caused by human intrusions and disturbances. The gap analysis results identified the in situ and ex situ conservation for 18 taxa of Arabian Verbascum, revealing that 70% of its populations occur outside protected areas (PAs) and 30% occur within PAs. In addition, the in situ gap analysis identified six complementary PAs and eight complementary sites within PAs for more active in situ conservation, four of which were located outside of PAs where Other Effective Conservation Measures (OECMs) could be implemented. The ex situ gap analysis revealed that not enough Arabian Verbascum taxa are conserved in international or national gene banks; thus, there is an urgent need for ex situ collection for all Verbascum taxa, focusing on hotspot areas outside PAs. Overall, the outcomes of this thesis have provided systematic knowledge and insight into the genus Verbascum, as well as recommendations that can aid wildlife conservation authorities on the Arabian Peninsula to meet their targets for conserving Verbascum diversity.