The genus Ptilostemon is represented in Morocco by four geographically and edaphically vicariant species. This contribution summarizes and expands the knowledge of distribution, ecology and phytosociology for P. leptophyllus. The species is endemic to the Central and Eastern Rif Mts, with an outpost in the Tazzeka Mts of the N Middle Atlas. It is strictly acidophilous and colonizes fissures of schist bedrock and moderately moving micaschists, mostly in the meso-Mediterranean bioclimate at 1000–1300m altitude. P. leptophyllus occurs in three different communities: (1) P. leptophyllus-Antirrhinum tortuosum community in the semi-arid, winter-cold Eastern Rif Mts around Tizi Ouzli; (2) Echium canum-Rumex thyrsoides community in the semi-arid, winter-mild lowlands of the Oued Rhis; (3) Convolvulus dryadum-Silene martyi community in the subhumid, meso-Mediterranean bioclimate. In all three communities caespitose hemicryptophytes are the predominant life form and Rif endemics such as P. leptophyllus, Convolvulus dryadum, Silene martyi and S. ibosii are a prominent chorotype. The pioneer character of other Ptilostemon species and the role of the rock environment as an evolutionary trap are discussed.