, Volume 140, Issue 2, pp 221-244

The phytogeographical significance of S.W. Morocco compared to the Canary Islands

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Abstract

A phytogeographical comparison of S.W. Morocco (the 'Argan area' western part of the Anti-Atlas mountains) and the neighbouring Canary Islands is performed in order to determine whether or not this original North-African area must be included in the Macaronesian sub-region. Patterns obtained with some species' life attributes (growth forms, succulence, dispersal) and biogeographical spectra show that, in spite of some similarities regarding climate, flora (presence of succulent species and endemics common to the two areas) and landscape in the lower zones (infra- and thermo-Mediterranean 'étages'), S.W. Morocco belongs to the Mediterranean sub-region. Characteristic features are the high percentages of Mediterranean indigenous annuals and phanerophytes, and the low level of adaptive radiation compared to the Canary Islands. Nevertheless, some parts of this Moroccan area have acted as major refugia for the Tertiary paleoflora (e.g., Aeonium arboreum, Davallia canariensis, Dracaena draco subsp. ajgal, Sonchus pinnatifidus), especially in the newly described rupicolous communities. Contrasting reliefs and fog precipitation induced by the nearby Atlantic Ocean explain the moderate impact, in these regions, of drastic climatic changes since the Pliocene period.