Taxus baccata in Morocco: A tree in regression in its southern extreme

The knowledge on chorology of species is basic for biogeographic and ecological studies and for conservation actions. The data on the chorology of Taxus baccata in Morocco have not been studied. The bibliographic resources, herbarium material, unpublished data of several botanists and the authors’ field notes have been reviewed. Two yew populations on Jbel Lakrâa in the Rif and near Bekrit in the Middle Atlas were measured to verify demographic structure and health conditions. The Maxent model of predicted habitat based on bioclimatic variables was used to evaluate the potential geographic range of T. baccata. The species occurs in the mountain areas of northern Morocco: in the Rif, the Middle and High Atlas, at altitudes between (500) 1200 and 2000 (2350) m. In the High Atlas, it reaches its southernmost locations within the geographic range. The populations represented by the highest number of individuals are found in the Western Rif and Middle Atlas, while from the High Atlas only single, isolated individuals are known. The yew occurred preferably in forests of Cedrus atlantica, Abies maroccana, groves of Betula fontqueri, Ilex aquifolium and Prunus lusitanica and in riparian forests located in narrow gorges. Seedlings were observed only at single localities. The population of T. baccata in the Rif presented a good health condition with successful regeneration, while the population in the Middle Atlas was in a much worse state, where only 4-8 m high yews were observed, without natural regeneration. The Maxent model of predicted habitat, based on bioclimatic variables, suggests that T. baccata could occur today in much broader mountainous areas in Morocco, especially in the Rif and Middle Atlas. However, the progressive decline of this species in Morocco indicates the significant importance of other factors on yew distribution, including microsite conditions and human pressure. Taxus baccata in Morocco is in regression at most of its localities and should be treated as a vulnerable species. Measures to ensure the yew’s conservation are needed, especially at its southernmost localities in the High Atlas.