Faunistic knowledge and insect species loss in an urban area: the tenebrionid beetles of Rome

Abstract

I used data on tenebrionid beetles (Coleoptera Tenebrionidae) accumulated in entomological collections from urban Rome to describe how faunistic knowledge developed over time and how species were lost because of increasing urbanization. Data spanned from 1881 to 2000. This period was divided into decades and for each decade various non parametric estimators of species richness were calculated. A species accumulation curve was best modelled using Clench asymptotic function. A reconstruction of extinction trends from 1881 to 2000 indicates a decline in species richness with increasing rate of extinctions. Discovery and extinction curves met at the 9th decade. All non parametric estimators had an erratic behaviour at low sampling efforts, but they tended to converge after the 6th decade, when number of collected specimens increased substantially. In general, sampling effort was not uniform among decades, and this affected negatively accumulation curves. If sampling was uniform, a quarter of collected specimens would be sufficient to collect 95 % of species. While accumulation of faunistic knowledge proceeded with decreasing rates, species extinction was rapidly increasing. Examination of museum specimens is therefore essential to reconstruct species occurrence in the past and to plan specific research to evaluate species extinction.