Urban biodiversity hotspots are not related to the structure of green spaces: a case study of tenebrionid beetles from Rome, Italy

At global and regional scales, area prioritisation is frequently done by the identification of hotspots based on species extinction risk. The logic of the hotspot identification has never been used in urban contexts. In this paper, the tenebrionid beetles (Coleoptera Tenebrionidae) of urban Rome were studied as an exercise to show how the hotspot approach can be profitably used in an urban area to identify priority areas for biodiversity conservation. For this, tenebrionid species from 16 green spaces were scored according to their vulnerability on the basis of their geographical distribution, habitat specificity and abundance. Species vulnerability scores were then used to calculate two indices of area prioritisation (the Biodiversity Conservation Concern and the Biodiversity Conservation Weight) for each green space. Values of these indices were correlated with site characteristics and compared with those obtained from other, more natural contexts. Except for distance to other sites, no significant correlation was found between conservation values and site characteristics, which indicates that the conservation importance of green spaces cannot be predicted on the basis of their geographical characteristics, but must be established on the basis of the species that they actually host. The importance of urban green spaces for biodiversity conservation may be questioned because of the large presence of ubiquitous and alien species in urban areas. Conservation values obtained for tenebrionids of green spaces in Rome are similar to those of various animal groups in more natural contexts and hence highlight the actual importance of green areas for insect biodiversity conservation.