Aquatic macrophytes and vegetation in the Mediterranean area of Catalonia: patterns across an altitudinal gradient.

Abstract

Even though aquatic macrophytes are key species in freshwater bodies and some of them are rare and vulnerable, aquatic macrophytic vegetation in the Mediterranean area is poorly known. Here we aim at identifying diversity patterns, both at the species and vegetation levels, from Catalonia (NE Spain), an area which holds a rich variety of aquatic ecosystems situated along a wide altitudinal range. More than 20,000 citations concerning 120 aquatic vascular plant species and 235 phytosociological relevés are studied. Data are obtained mainly from the Biodiversity Data Bank of Catalonia (BDBC) plus unpublished records. Aquatic macrophytes are present in 94% of the total 10 × 10 km2 UTM squares covering the studied area and 82% of the aquatic macrophytes reported from the Iberian Peninsula are listed in Catalonia. This illustrates that species richness in this small area is high, in accordance with its geomorphological and water body diversity. Coastal wetlands, deltas and alpine lakes arise as diversity hot spots, with altitude being a major factor in determining species distribution and richness. DCA ordination of the BDBC relevés also showed a high relevé dispersion for some submerged macrophyte associations like Potametum denso-nodosi, which can be explained either by inaccuracy when defining the association or by an erroneous identification of some relevés. Moreover, the compiled relevés come from a 8% of the studied territory, indicating that much effort has to be devoted to the study of these communities and their distribution.