Sideritis royoi (Lamiaceae): A New Orophilous Species from Northeastern Spain

Sideritis royoi is found in the rocky limestone habitats of the Port Massif (southern Catalonia, Spain). The species was first collected by the local botanist Lluís de Torres in the late part of the 20th century, but the specimens have remained unidentified positively in herbaria for over 40 years. Sideritis royoi likely belongs to section Sideritis subsection Hyssopifoliae and shows some morphological affinities with the relatively widespread South European species S. hyssopifolia L., but it differs from this species because it has subspinescent upper leaves, the main surfaces of its leaves are glabrous or glabrescent, the main abaxial surface of its bracts is without eglandular hairs, and due to the fact that it has shorter inflorescences. Weaker similarities have also been observed with some species belonging to S. subsection Fruticulosae Obón & D.Rivera. In this paper, a description for the new orophilous species is provided, along with a detailed illustration, field photographs, and a comparison with closely related species. We include an assessment of its conservation status and a dichotomous key for the identification of all the species of Sideritis subsection Hyssopifoliae.