Χωρική ετερογένεια και ποικιλότητα ειδών στις προστατευόμενες περιοχές της Ελλάδας

Abstract

In this doctorate thesis the main biodiversity patterns were investigated at multiple scales of analysis. There is an increasing need for preserving and restoring the natural environment due to the continuous degradation caused by human presence. As study areas were selected the aquatic ecosystems included in the Natura 2000 network. Three were the levels of biodiversity that were analyzed for the current study: (a) aquatic ecosystem’s landscape, (b) aquatic ecosystem’s species (freshwater fish fauna) and (c) aquatic ecosystem’s habitat types. At the landscape level, the protected areas including reservoirs were compared to those including lakes and rivers. The landscape structure and habitat type composition of reservoirs were completely different to lake and rivers. The intensity of human presence, as this was measured by the presence of arable land and settlements did not differ significantly among the three types of ecosystems. It appeared that reservoir ecosystems were completely different, compared to those of lakes and rivers and the management strategies applied should be different among the three types of ecosystems. The management bodies should apply different measures for the preservation and restoration of the unique biodiversity of these ecosystems. At the species level, the factors determining the composition of native fish fauna of freshwater ecosystems were determined. In the analysis were examined local environmental variables, as well as species dispersal ability, calculated in terms of straight-line Euclidean distances between ecosystems. The analysis was carried out for aquatic ecosystems occupying a large part of the country and then for the different biogeographical zones. At both levels, the importance of species dispersal was greater than that of local environmental variables. At the country level, species biogeography was the most important factor determining community composition. It was described by the routes of dispersion these species followed when inhabiting the Balkan Peninsula. The natural barriers of seawater and Pindus Range did not allow species dispersal through all freshwater ecosystems of Greece. At the level of biogeographical zones, species dispersal seemed to be once again the main factor determining species community composition compared to environmental parameters. In conclusion, species dispersal ability, biogeography and the presence of natural barriers determined species community composition more than environmental variability. At the habitat type level, the factors determining habitat type composition in most Greek protected aquatic ecosystems were assessed. The relative contribution of geographical, spatial and climatic measures was estimated for the protected aquatic ecosystems of Greece. Climatic variables were the main determinants of habitat type composition compared to spatial and geographical parameters. More specifically, precipitation measures and even more their extreme values were the main determinants of richness patterns, compared to temperature measures, which seemed to have had a smaller contribution. The assessment of habitat type richness is of great importance as it could give an estimate for the effects of climatic conditions on patterns of biodiversity. Spatial pattern analysis can provide the possibility for a better estimation, description and understanding of the structure of an aquatic ecosystem’s landscape. At the species level it is important for researchers to consider both species biogeography and dispersal ability, as well as the structure of landscape matrix. At the habitat type level the role of spatial pattern seemed to be secondary while the role of climate was the main determinant of richness patterns. It became apparent that at each level of observation (aquatic ecosystem, species in the ecosystem and habitat types comprising the ecosystem’s landscape) the relative contribution of spatial structure, dispersal limitation and climatic variables, to determining biodiversity patterns varies.