CONTRIBUTION TO THE KNOWLEDGE OF SPANISH URBAN BRYOFLORA

We have studied all the bryophyte species that live in more than three out of fourteen Spanish cities. Here we present data on the genetic, physiological, structural and ecological characteristics that are thought to be relevant in defining << urban >> bryophytes. These characteristics were present in 12 << urbanicolous species >>: Tortula muralis Hedw., Bryum bicolor Dicks., Funaria hygrometrica Hedw., Bryum capillare Hedw., Bryum argenteum Hedw., Barbula unguiculata Hedw., Grimmia pulvinata (Hedw.) Sm., Didymodon fallax (Hedw.) Zander, Didymodon vinealis (Brid.) Zander, Lunularia cruciata (L.) Lindb., Orthotrichum diaphanum Brid. y Pseudocrossidium hornschuchianum (K.F.Schultz) Zander. The features which seem responsibles for the adaptation of the bryophytes to the urban environment are: high capacity for vegetative propagation, the presence of protective flavonoids, dioecia and growth forms with short turfs, cushions or mats. Regarding the habitats and their ecological conditions, they are saxichasmophytes or terricolous, basophilous, nitrophilous, photophilous and trampling-resisting. They show enhanced survival and luxuriance under a regime of nutrient flushing, many xerophytic adaptations, with a colonist life strategy and finally, they are toxitolerant or moderately toxitolerant to the SO2, surviving in pollution levels of over 50-60 mu g/m(3).