Résumé
In North Africa, peat mosses (genus Sphagnum) are rare and restricted to a few wet habitats distributed in two main regions: northern Morocco and the northern Algerian-Tunisian boundary. Based on herbarium specimens from 1861 to 1965, on recent collects and on floristic surveys, the present paper addresses the taxonomy, distribution, history and biogeographical significance of peat mosses of the Tingitanean-Rifan range. On the first hand, our results lead to the discovery of a new species for Morocco (Sphagnum subnitens), previously only known in North Africa from three ancient herbarium specimens from Kroumiria (northwestern Tunisia). Because S. subnitens was not recovered in Tunisia for more than 50 years, its North African distribution is thought to be now restricted to the fen complex of Krimda (Larache region), where it forms 20-30 hummocks in at least three places. On the second hand, our results confirm the presence of Sphagnum auriculatum (sometimes noted S. rufescens or confused with S. flexuosum) in two zones: Krimda and Jbel Bou Hachem. This species probably still occurs in some other mountains of Jebala Range (Jbels Alam, Sougna and Khezana), but it disappeared from its northernmost locality (Jbel Dhar Zhirou), because of human-induced disturbances. Palaeoecological data indicate than most of the sedge fens harbouring Sphagnum populations originate from past alder-can-communities, which decline was triggered by human activities during the last millennia. The occurrence of such wetlands with northern affinities within the Mediterranean vegetation of North Africa constitutes a biogeographical enigma. The understanding of the influences of Quaternary climate variations and long-distance transport would be of major concern for the sustainable conservation of these exceptional and highly threatened habitats.