Use of insect distribution across landscape-soil units to assess conservation priorities in a Mediterranean coastal reserve: the tenebrionid beetles of Castelporziano (Central Italy)

We investigated the conservation concern of landscape-soil units within Castelporziano lowland forest (a natural reserve of 6,000 hectares facing the Tyrrhenian Sea) using tenebrionid species vulnerability as defined by the Kattan index, which is based on species rarity, and IUCN categories. Species rarity was evaluated according to various measures of geographical distribution, habitat specialization and population size on a regional level. Measures of species vulnerability were combined into two indexes of conservation concern for each landscape-soil unit: (1) the Biodiversity Conservation Concern index, BCC, which reflects the average rarity score of the species present in a site, and (2) the Biodiversity Conservation Weight, BCW, which reflects the sum of rarity scores of the same species assemblage. Because the same species was subject to multiple evaluations under different criteria, we obtained various series of BCC and BCW values. BCC and BCW provided complementary information and the use of different scoring schemes of species vulnerability produced correlated, but not identical conservation ranking in landscape-soil unit prioritization. Forests, wetlands and beach-dunes were identified as high priority units, whereas dry pastures, traditional crop mosaics, pinewoods and maquis/garrigue shrublands, were identified as medium–low priority units. Tenebrionids were proved to be particularly useful as a bio-indicator group in coastal areas because they include both sand-dwelling and saproxylic species, being distributed, with distinct communities, in all coastal biotopes