Abstract

MULLER, Jonas  and  DEIL, Ulrich. Ecology and Population Structure of Two Heathland Species, Endemic in Southern Portugal. Centaurea crocata and Centaurea fraylensis (Asteraceae). Silva Lus. [online]. 2002, vol.10, n.2, pp.151-170. ISSN 0870-6352.

Distribution, sociology and population structure of Centaurea crocata and C. fraylensis were studied in the Serra de Monchique, the mountainous hinterland of the Algarve. The Serra is the main area of distribution of Centaurea crocata and the exclusive area of distribution of C. fraylensis. Field data were collected from April to July 1998. 51 phytosociological relevés were made in all kinds of habitats where Centaureae occurred. To analyse their population structure, vegetative morphometric parameters (plant height, rosette diameter, root collar diameter) were measured on 434 individuals of C. crocata and 296 of C. fraylensis. All studies were restricted to non-destructive observations. The species are restricted to the more humid western and northern parts of the Serra. C. crocata shows a wider ecological range than C. fraylensis with respect to the number of populations (38; 15), altitude (290-840m; 300-500m a.s.l.), substrate (schists and syenite; only schists) and total distribution. Both species are constant character species of the Querco-Stauracanthetum, a vegetation type which originated on wind exposed mountain ridges with shallow soils in the mesomediterranean belt. The main strategy of the Centaurea-species is that of a sitter; they can resprout from the napiform root after damage or burning. The generative reproduction strategy is supported by vegetative propagation. If vital populations are nearby, they are able to colonise roadside verges, forest pathways, firebreaks and terraced slopes with Eucalyptus plantations. There, they are associates of [Ericion umbellatae]-basal communities. The pioneer character of C. crocata is more distinct than that of C. fraylensis. The enormous variability of all the measured vegetative parameters does not allow one to draw conclusions about the age structure of the populations studied or to look for correlations between population structure and habitat. Both species must be considered as potentially endangered by the current land-use changes in the Serra. Finally, some deficits in the knowledge of their reproductive biology and further research topics are mentioned and the needs for conservation efforts are strengthened.

Keywords : Serra de Monchique; Ericion umbellatae; plant sociology; population biology; reproduction; conservation biology; endangered plants.

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