Common and rare Swedish vertebrates — distribution and habitat preferences

Data have been compiled on the distribution, habitat preferences and population sizes of 348 vertebrates reproducing in Sweden (excluding fish) and their species richness in different habitats and regions was investigated. Furthermore, we compared the habitat preferences and distribution of rare and common vertebrates. The relative species number (corrected for area) increases from the north (the hemiarctic/boreal zone) 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% of the land area excluding sea). Within woodlands, a large proportion of species occur in southern deciduous forests, in other deciduous forests and in mixed forests, while coniferous forests are less species-rich 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. Nationally rare species (<1000 individuals) have a smaller European range than common species, and they also have their European distribution centres further to the south than the common species. Of the species occurring in large parts of Sweden (that is, both in the north and the south) a low proportion (4.7%) are classified as rare compared with species 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 number of rare species and the total species number in 41 subcategory habitats, and the proportion of rare species is similar in most habitats. A more detailed analysis (including effects of both regions and habitats) suggests that the proportion of rare species in a region is a result of differences between latitudes, but also of different habitats (when corrected for latitude effects). There are differences in the proportion of rare species between the nine most species-rich orders (for example, there is a high proportion of rare species in the order Carnivora 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 habitat preferences and taxonomy on rarity. The focusing of conservation work on relatively species-rich habitats in southern and middle Sweden — such as some farmland habitats (that is, meadows and forest edges), marshes (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.