Distribution, ecology, and population structure of Senecio lopezii (Asteraceae) in the Serra de Monchique (SW Portugal)
The Serra de Monchique, a mountain chain in the hinterland of the Algarve Province, is characterized by a remarkable degree of floristic richness and endemism. Senecio lopezii, a tall-growing hemicryptophyte, is one of these endemic plants. We studied the local distribution, the ecological requirements, and the size and vitality of the populations in order to evaluate the vulnerability of this species with regard to disturbance by man and landuse changes. Between April and June 2001, populations observed in an area of 84 km² (= the central part of the Serra) were analysed in detail by non-destructive methods. A synopsis of the phytosociology and ecology of the species, based on literature including the Spanish populations in the Campo de Gibraltar (SW Andalusia), is presented. Senecio lopezii was discovered in the Serra de Monchique at only 5 localities, all in mid altitude (500 to 600 m a. s. l.) in the mesomediterranean bioclimatic belt on the northwestern, windward side of the Serra. The species is associated with the Sanguisorbo-Quercetum suberis quercetosum canariensis and its shaded fringes. It persists in Castanea sativa coppices, cultivated on sites with semi-deciduous oak forests as climax, when the topsoil remains intact. Population size ranges from 30 to 350 individuals, the total number is 920 specimens. Plant size and phenological stage were recorded for 258 individuals. Most of them (89 %) are sterile adults, which persist in dark conditions under a closed tree canopy. Flowering starts at a specific plant size and increases with growing rosette diameter, respectively, increasing number of leaves. To get information about the age structure, the life cycle, the role of the seed bank, and the effect of clearings of the shrub layer, further investigations are necessary. Senecio lopezii is a rare species as regards distribution, habitat specification and population size. It must be considered as a potentially endangered species, because it will not tolerate the transformation of oak forests into Eucalyptus plantations.
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