These statements aim to determine whether the term Moroccan Macaronesian sector should be retained or discarded; the scientific evidence is presented in chronological order.
Based on the presence of Macaronesian species or vicariants of Macaronesian species, Braun-Blanquet and Maire (1924) were the first to consider the presence in Morocco of a Macaronesian enclave, located almost exclusively in the Argan tree sector (Braun-Blanquet and Maire, loc. Cit., p. 64). To explain the affinities between the southern Moroccan Atlantic coast and the Canary Islands, they assumed a direct connection between the islands and the continent, certainly during the Tertiary period. It is now known that the islands forming the five archipelagos of Macaronesia are all of volcanic origin, that their ages range from 0.27 Ma (Pico Island, Azores archipelago) to 29.5 Ma (Selvagens Islands) (Freitas et al., 2019), and that they have never been connected to any continent.
A few years later, the Catalogue des plantes du Maroc (Jahandiez & Maire, 1931, vol. 1, p. XI) presented a map of the geographical divisions of Morocco that included a Moroccan Macaronesian sector. The authors indicated that the map was based on the note by Maire and Emberger (1928), which provided an overview of phytogeographical knowledge of Morocco at the time. The document highlighted, along the Atlantic coastline, a Moroccan Macaronesian sector extending from Cape Cantin (now Cape Beddouza, north of Safi) to Agadir, justified by the relatively high proportion of Canary Island plants in its flora. Maire and Emberger (loc. cit., p. 284) stated that this Moroccan Macaronesian sector was, for the phytogeographer, inseparable from the Canary Islands. The Sous, characterized by Argania and Ziziphus savanna, corresponded, according to these authors, to the south-western steppe sector.
In 1934, at a congress in Rabat, Emberger, seeking to summarize floristic knowledge of Morocco, proposed dividing the country into six floral domains. He recognized only along the Atlantic coast a Morrocan-Macaronesian sector, characterized by a list of Canary species borrowed from Braun-Blanquet and Maire (1924). In contrast, the Sous was placed within a Saharo-Mauritanian domain, characterized by a relatively high contingent of tropical species or species related to tropical types (including Argania, Acacia gummifera, and cactiform euphorbias).
In a 1952 note, Sauvage recalled the existence along the Moroccan Atlantic coast of a zone referred to by phytogeographers as a Macaronesian enclave. Seventeen endemic taxa common to this coastal area and the Macaronesian islands, as well as twelve vicariants, can be recognized there (Peltier, 1973).
In a synthesis work, Monod (1957) proposed the major chorological divisions of Africa. within the Mediterranean region, and again only along the Atlantic coast, he recognized a Macaronesian domain.
In 1978, Quézel, in an analysis of the Mediterranean and Saharan flora of Morocco, also referred to a Moroccan Macaronesian sector, but on the Atlantic coast of Morocco, especially in the Sous Valley, whose essential physiognomic element is Argania spinosa. As thus defined, the Moroccan Macaronesian sector extended inland, reaching the western slopes of the High Atlas as well as the Anti-Atlas. For the first time, it was stated that the Moroccan Macaronesian sector ultimately corresponded to the distribution area of the Argan tree. Before 1978, all researchers had limited the Moroccan Macaronesian sector to a narrow coastal strip along the Atlantic coast, from the province of Tarfaya in the south to Safi in the north (Sauvage, 1952).
Sunding (1979), in an article devoted to the origin of the Macaronesian flora, considered that the Moroccan enclave formed part of Macaronesia* (fig. 1), and Kunkel (1980) adopted this view (in Del Arco Aguilar & Rodríguez Delgado, 2018, p. 51). The Moroccan Macaronesian sector also appears on the maps of Peyerimhoff (1946) and König & Bley (1988) (in Beyhl et al., 1995). On König & Bley’s map, it is labeled “vegetation rich in succulent plants.” Lobin (1982) and Biondi et al. (1994) likewise mention a Moroccan Macaronesian sector because of the large number of taxa shared with the Macaronesian islands.
The map of the biogeographical divisions of the Sous watershed (Peltier, 1982) was established according to the divisions proposed by Quézel (1978). However, it restricted the Moroccan Macaronesian sector to a narrow coastal and subcoastal strip about thirty kilometers wide, corresponding approximately to the cactiform euphorbia steppe, a unique steppe in North Africa shared with the insular Atlantic arid zones of the Canary Islands and Madeira (Le Houérou, 1995). The inland parts of the Sous watershed correspond to the North African Mediterranean domain (Quézel, 1978).
In 1982, Barbéro et al. analyzed the phytosociological structures of southwestern Morocco from Essaouira to the Drâa Valley along the coast, as well as in the Sous Valley. The order Acacio-Arganetalia was described, with two alliances (Acacion gummiferae and Senecio anteuphorbii–Arganion spinosae). From a biogeographical standpoint, the authors stated that the belonging of southwestern Morocco to the Mediterranean region, and not to the Macaronesian region, was evident (Barbéro et al., p. 314), and that the term Moroccan Macaronesian sector should be abandoned (ibid.).
In 1994, Benabid and Fennane summarized knowledge on Moroccan vegetation. They indicated that the Argan tree is an important feature of the Moroccan Macaronesian sector (p. 31). Consequently, the presence of this sector in Morocco was accepted. The authors noted that the potential communities of this sector belong, from a phytosociological standpoint, to the order Acacio-Arganetalia (Barbéro et al., 1982).
Gehu and Biondi (1996) described the psammophilous plant communities of dunes and sandy deposits along the southwestern Moroccan coast. Their originality lies in the high percentage of species shared between Morocco and the Canary Islands. In this publication, reference is made to a so-called Macaronesian Morocco, but the authors do not clearly take a position in favor of the presence of a Moroccan Macaronesian sector along the southwestern coasts.
Kim et al. (1996), in a study on the adaptive radiation of Sonchus subg. Dendrosonchus in the Canary Islands and concerning the delimitation of the Macaronesian distribution area, adopted Sunding’s (1979) viewpoint, reproducing in full figure 1 of his publication.
In 1999, Quézel and Médail carried out a detailed phytogeographical comparison of southwestern Morocco and the Canary Islands to determine whether the distribution area of the Argan tree in the infra- and thermo-Mediterranean arid and semi-arid belts should be included within a Macaronesian subregion. This analysis was based on comparisons of phytogeographical spectra, species life attributes (growth forms, succulence, dispersal), and homologous vegetation structures.
The conclusion was unequivocal: although the presence of succulent species and particular climatic conditions implies a close relationship with certain zones of the Canary Islands, southwestern Morocco must be regarded as a major refuge area for thermo-xerophilous species (Euphorbia, Caralluma, Aeonium, Dracaena , etc.) of the North African Mediterranean domain (Quézel & Médail, 2003, p. 64), and not at all as a Macaronesian enclave in Morocco. The main characteristics of this entity are the high percentages of Mediterranean native annuals and phanerophytes and the low level of adaptive radiation compared with the Canary Islands (Quézel & Médail, 1999).
In conclusion, the coastal and subcoastal zone of southwestern Morocco may be considered, from both physiognomic and historical perspectives, as an entity with Macaronesian affinities, at least when referring to the steppe of cactiform and pachycaulous euphorbias, which represents a unique type in North Africa. However, from a strictly phytogeographical and phytosociological standpoint, southwestern Morocco does not correspond at all to a Macaronesian enclave. Logically, the most recent synthesis on the world’s biogeographical regions places southwestern Morocco within the Mediterranean region (Loidi & Vynokurov, 2024).
The recent synthesis on Macaronesia (Fernández-Palacios et al., 2024) indicates that the integration of the African coastal enclave into the Macaronesian biogeographical region remains to be confirmed. This reservation is notably linked to the importance of back-colonization processes—dispersal of species from the islands to the continent—already documented in several plant lineages (Aeonium, Androcymbium, Convolvulus, Lotus, Euphorbia).
*Macaronesia is defined here in the classical sense, by comparing the flora and vegetation of the islands. The coherence and validity of Macaronesia as a biogeographical unit are called into question when one attempts to define it using marine groups with very different dispersal capacities (Freitas et al., 2019).
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Posted by Jean-Paul Peltier.