DNA barcoding of the genus Verbascum (Scrophulariaceae) in the Arabian Peninsula

Verbascum and Rhabdotosperma are members of the family Scrophulariaceae. The first genus comprises approximately 360 species from almost all parts of the world, while the second contains a total of 8 species from tropical Africa and the Arabian Peninsula. Since 1977, the relationships between Verbascum and Rhabdotosperma continue to be contested. The present study aims to present the phylogenetic relationships and status among Verbascum species in the Arabian Peninsula. For phylogenetic analyses, maximum parsimony and Bayesian inference were performed. In total, 236 DNA sequences from 59 specimens of Arabian Verbascum were analysed. The phylogenetic analysis of one nuclear (ITS) and three chloroplastic (rbcL, matK, trnL) markers confirmed the monophyly of Verbascum, including the genus Rhabdotosperma. In addition to presenting novel phylogenetic relationships among the different Verbascum species in the Arabian Peninsula, our study reduced the species count of Arabian Verbascum to 16. Moreover, the phylogenetic analysis strongly supports the reinstatement of the genus Rhabdotosperma into Verbascum based on the Bayesian and maximum parsimony analyses.