Santolina L.

Genus composed of about 20 Euro-Mediterranean species, particularly diversified in the Iberian Peninsula, with 3 species in North Africa, 2 species are endemic (S. adscensionis and S. africana) and a further species is endemic to the Iberian Peninsula, Malta and NW Africa (S. pectinata). Although they are small in size (just 80 cm in height), they are often dominant species in certain plant formations and give character to the landscape.

A very closely related taxon is the genus Pentzia Thunb, consisting of about 25 species, mostly from arid and desert areas of southern Africa, with 2 subshrubby species in the N. P. monodiana Maire (Tamahaq: Tehatit) resembles Santolina spp. for its size and general appearance, but the achenes have a pappus in the shape of a clearly liguliform membranous corona. This is a subshrub that barely reaches 50 cm in height, highly branched, with old branches with suberose bark and young branches with whitish sericeous indumentum, middle and upper leaves pinnatipartite and capitula c. 1 cm in diameter, solitary, longly pedunculate, with involucral bracts, linear-lanceolate, with whitish scarious apex and all flowers in disc florets, golden-yellow. Endemic to the central Algerian Sahara, to the highlands of Ahaggar  and Tassili n’Ajjer. P. hesperidum Maire & Wilczek is a small woody subshrub, of just 20 cm in height, with fleshy leaves, the middle and upper leaves with denticulate margin and outer involucral bracts ovate or oblong, with scarious pale brown apex. Endemic to the coastal cliffs and coastal plains of the Moroccan Sahara.

Also closely related is the genus Cladanthus Cass., composed of 5 Mediterranean species, all represented in North Africa. They are annual or perennial herbaceous plants, with a single suffruticose species. C. scariosus (Ball) Oberpr. & Vogt (Santolina scariosa Ball, Ormenis scariosa (Ball) Litard. & Maire) is similar to Santolina and Pentzia species by its appearance, size (just 50 cm in height) and solitary, longly pedunculate capitula. However, this subshrub clearly differs by having capitula with peripheral flowers in ray florets (with 3 lobes) as well as disc florets. Also, unlike Santolina and Pentzia species, the capitula present interfloral bracts in the receptacle. It is an endemic Moroccan species occupying arid mountainous areas at low and mid altitude in the Anti-Atlas, High Atlas, Middle Atlas and plateaux of eastern Morocco.

Currently, none of these species have been assessed at a global level in the IUCN Red List of Threatened Species. In the Livre Rouge de la flore vasculaire du Maroc (Fennane, 2021) P. hesperidum has been considered as Vulnerable (VU) and C. scariosus as Near Threatened (NT). In Algeria P. monodiana is included in the List of protected non cultivated flora (Executive Decree 12-03 on 4-Jan-2012).