Floristic data of the upper Segre and Llobregat basins. IV

This work provide new data and precisions about the regional flora of the upper Segre and Llobregat basins (Eastern Pyrenees), which relate largely to alien plants. Regarding native
plants it is noteworthy Oxybasis rubra, new for the Catalan flora, and the first detailed information about the only Pyrenean population of Myosotis minutiflora. In regard to the alien taxa we remark the detection of Cardamine occulta populations in natural and seminatural fluvial habitats (margins of three reservoirs and one river) because in Europe the occurrence of this species outside urban habitats is very rarely reported. The local naturalisation of Prunus virginiana in the upper Segre river has been confirmed, and we have also obtained data that suggest an initial naturalisation of Fraxinus americana and Ulmus laevis. In this river we have also observed some populations of Salvia hispanica and Physalis peruviana, but their naturalisation is uncertain.