Floristic distinctiveness of the low and mid-altitude peat-rich heathlands of the western Iberian Peninsula and northwestern Morocco

Abstract

Peat-rich heathlands, characterized and dominated by Ericaceae and Genisteae, are the southernmost outliers of the class Calluno-Ulicetea in the Mediterranean region. They occur in small and isolated patches along the Atlantic façade of the SW Europe on acidic soils with peat formation and on hydromorphic podzols. Such sites could have acted as refugia for hygrophilous plant during dry climatic phases in earth history. Recent phylogeographic studies of the Genista anglica-ancistrocarpa complex showed a clear separation of a clade, distributed in Western Europe and the Northern Iberian Mountains (Genista anglica), and a clade of SW-Iberian and NW-Moroccan distribution (G. ancistrocarpa) indicating long-term isolation (possibly since the end of the Tertiary) upcoming form intricate paleogeographic and paleoclimatic patterns. In order to access if such long-term patterns are nowadays traceable at the community level, we analysed all the available data of the Genistion micrantho-anglicae from the Iberian Peninsula and NW Morocco. The agglomerative hierarchical clustering shows a clear separation of two clusters: A) Ulici lusitanici-Genistion ancistrocarpae all. nov. hoc loco (typus: Cirsio welwitschii-Ericetum ciliaris) and B) Genistion micrantho-anglicae. This floristic differentiation is congruent with ecological and phytogeographical patterns: The first alliance is distributed along coastal areas and usually at lower altitudes within thermo- and mesomediterranean bioclimatic belts, while the associations of the latter occur at higher altitudes and in the interior and northern parts of the Iberian Peninsula, under temperate macrobioclimate. Both alliances have their own character taxa (some of them geographical vicariants) and are furthermore differentiated by transgressive species, which add further biogeographic information coming from the surrounding vegetation matrix. Finally we underline the conservation value of heathy peatlands as a refugium for the southernmost populations of Atlantic plant species in the Mediterranean region.info:eu-repo/semantics/publishedVersio