COMMON AND RARE SWEDISH VERTEBRATES - DISTRIBUTION AND HABITAT PREFERENCES

Data have been compiled on the distribution, habitat preferences and p opulation sizes of 348 vertebrates reproducing in Sweden (excluding fi sh) and their species richness in different habitats and regions was i nvestigated. Furthermore, we compared the habitat preferences and dist ribution of rare and common vertebrates. The relative species number ( corrected for area) increases from the north (the hemiarctic/boreal zo ne) to the south (the temperate/hemiboreal zone). The relative number of species in major habitats is highest in farmland, lakes and running waters, and possibly also in the sea. However, the absolute number of species is highest in woodland, the dominant habitat in Sweden (56% o f the land area excluding sea). Within woodlands, a large proportion o f species occur in southern deciduous forests, in other deciduous fore sts and in mixed forests, while coniferous forests are less species-ri ch when the habitat area is taken into account. In farmland, the most species-rich habitats are meadows and forest edges, while marshes are the most species-rich habitats amongst lakes and running waters. Natio nally rare species (<1000 individuals) have a smaller European range t han common species, and they also have their European distribution cen tres further to the south than the common species. Of the species occu rring in large parts of Sweden (that is, both in the north and the sou th) a low proportion (4.7%) are classified as rare compared with speci es occurring mainly in the north (20.6% rare) or mainly in the south ( 31.6% rare) of Sweden. There is a positive correlation between the num ber of rare species and the total species number in 41 subcategory hab itats, and the proportion of rare species is similar in most habitats. A more detailed analysis (including effects of both regions and habit ats) suggests that the proportion of rare species in a region is a res ult of differences between latitudes, but also of different habitats ( when corrected for latitude effects). There are differences in the pro portion of rare species between the nine most species-rich orders (for example, there is a high proportion of rare species in the order Carn ivora and a low proportion in the order Rodentia), but the proportion of rare species in these orders is not independent of the habitats in which they occur, making it difficult to separate the effects of habit at preferences and taxonomy on rarity. The focusing of conservation wo rk on relatively species-rich habitats in southern and middle Sweden - such as some farmland habitats (that is, meadows and forest edges), m arshes (in connection with lakes and running waters) and forests with a relatively high proportion of deciduous trees - is of high priority if the conservation of biodiversity is a main goal. These are also the habitats with a high number of rare and red-listed species.