Urban bryophyte floras of Spain: a meta-analysis

Bryophytes constitute an important part of the unmanaged plant diversity of urban areas. They represent, directly and indirectly, an important food, shelter and microhabitat-engineering resource allowing the establishment of other organisms, thereby increasing the biodiversity of urban areas. However, their contribution to urban biodiversity is generally overlooked and poorly understood. In this study, we compared pre-existing data from 23 Spanish urban bryophyte floras and used taxon accumulation curves and ordination analyses to reveal emergent patterns related to urban biodiversity in Spain. The compilation of these 23 floras revealed 286 bryophytes represented in urban areas in peninsular Spain and the Balearic Islands, including 2.80% and 3.50% of taxa considered under some threat category at the European and Iberian scales, respectively. Taxon richness and diversity varied greatly across cities and were strongly affected by climatic characteristics and extension of the studied cities. Ordination analyses showed an alignment of the different floras with the geographical location of the cities. Eurosiberian (Atlantic) and eastern and southern cities showed a higher taxon richness compared with cities from central Spain, which showed taxon assemblies comprising the commonest and widespread taxa. We also found that taxon richness was influenced by methodological factors (i.e. sampling intensity and the time the study was done). Our study results suggest a need for adequate sampling of habitat heterogeneity within the urban landscape and point to the contribution of bryological knowledge to our understanding of the biodiversity of urban areas.