About plant and bird diversity patterns across wetlands of Sardinia and Sicily: implications for conservation

Wetlands are global hotspots of biological diversity, ecosystem productivity and economic activities. These also play fundamental roles in climate change regulation and mitigation. Mediterranean wetlands, in particular, are characterized by a long history of anthropization; even though they are still very important or vital habitats for many species. Understanding the relationships among different taxa is therefore fundamental for the conservation of these ecosystems. This research was undertaken to improve the knowledge about the floristic and bird composition in different types of wetlands in Sardinia and Sicily in order to evaluate if the richness and co-occurrence of vascular plants and birds vary among the different wetland categories. We compiled a presence/absence matrix of plants and birds for a representative set of wetlands, classified according to Ramsar categories, extent and number of habitats. Original sighting data were improved by all the available information obtained from the literature. The relationships between the richness of plants and birds’ presence were studied through regression analyses. A variance/covariance matrix for species was constructed to evaluate the binary correlation of site occupancy between species. Our results showed no relationship between plant and bird species richness, while differences among wetland types in both plant and bird richness were significant. Furthermore, plant and bird species richness showed a positive correlation with size and habitat diversity. The variance-covariance matrix showed significant relationships between bird and plant species whereas the co-occurrences of endangered bird and plant were not significant. The occurrence of different taxa in wetlands may be related to several reasons: random coincidence, interactions between taxa, a similar response to common factors, and response to different environmental factors that are spatially covariant. Poor correlation between bird and plant diversity could be also due to nesting systems, which often occur in species-poor sites, more correlated with a determinate type of habitat. These findings provide a baseline to understanding linkages between the diversity of organisms and constitute an important challenge for the knowledge of how ecological communities and processes are determined at both local and regional scales in order to develop an efficient network for the conservation of wetland biodiversity.