Insect rarity, extinction and conservation in urban Rome (Italy): a 120-year-long study of tenebrionid beetles

1. Urbanisation is an obvious cause of insect extinction, but few studies have investigated insect species loss in urban areas, and the importance of urban environment in conservation biology is controversial. 2. Urban Rome offered a unique possibility to study whether species rarity predisposes a species to extinction, and how urban green spaces are important in insect conservation. On the basis of records collected in more than one century, tenebrionid beetle extinction in Rome was related to a multidimensional characterisation of species rarity based on geographical range, ecological tolerance and local abundance. From these measures, a vulnerability index was derived. All measures of rarity and the vulnerability index were correlated with species decline: rare species disappeared earlier. 3. Identification of ecological correlates of extinction proneness is an important task in conservation biology, yet few studies have addressed this issue for insects. Tenebrionid extinction in urban Rome indicates that vulnerability measures based on rarity traits are strong predictors of species decline. 4. Most of tenebrionids living in urban Rome are not rare and the urban area is an important hold for few species of conservation concern. This suggests that contrary to current practice, insect conservation programmes in an urban area should be more addressed to single species action plans than protection of as many areas as possible.