Taxonomic, nomenclatural, and conservation notes to the Algerian-Tunisian endemic Thymus numidicus (Nepetoideae, Lamiaceae)

Thymus numidicus Poir. (Lamiaceae) is a species endemic to an extended area of the northern African coast, in Algeria and Tunisia, named “Kabylia-Numidia-Kroumiria.” This taxon was formerly regarded as restricted to siliceous substrata until the finding of a population on marly limestone from the “Mejarda Valley's region” in north-western Tunisia. Due to the differentiation of several morphological characters including mainly leaf color, shape and size, calyx, and corolla color and size, the collected material is illustrated and a subspecies new to science is here presented, Thymus numidicus subsp. vagaensis El Mokni & Domina. Discrimination of the new subspecies with T. numidicus subsp. numidicus is discussed; the ranges of variation in size and color of leaves, calyx, and corolla of the two subspecies are illustrated. Habitat, ecology, chromatographic profiles, and conservation issues are also considered. The lectotypes of the names Thymus numidicus Poir. and T. lanceolatus subsp. kabylicus Batt. are here designated and T. lanceolatus subsp. kabylicus is included among the synonyms of T. numidicus.