Distribution of the Italian fauna

The geographic information included in the Checklist is: a) distribution of terrestrial and freshwater species in 4 geographical regions of the Italian territory (North, South, Sicily, Sardinia); distribution of marine species in 3 areas (western basins, upper and middle Adriatic sea, remaining basins). The sectors are illustrated in the following map:

A preliminary analysis of the distribution of Italian fauna was discussed by Stoch (2000) for the invertebrates. The distribution of Italian species in the geographical regions used in the Checklist is reported in the following table:

Species numbers of total species of vertebrates (NtV) and invertebrates (NtI), excluding ‘protozoans’, compared with area of: northern Italy  (N); central and southern Italy (S); Sicily (Si); Sardinia (Sa); western Thyrrenian sea (3); northern and central Adriatic sea (4); southern Adriatic, Jonic sea and other seas (5)

Following these results, terrestrial and freshwater biodiversity shows a dramatic decrease from North to South. This “faunistic gradient”, already pointed out by other researchers (Massa, 1982; Contoli, Penko, 1996) as regards vertebrates, may be explained considering a “peninsular effect” (Stoch, 2000), which reflects the increasing difficulty of colonizing peripheral areas. Apart from history, the relative importance of further variables, like habitat diversity, disturbance, and climate, should be taken in account in the explanation of biodiversity patterns in Italy; moreover, less complete faunistic data are available for southern Italy (Stoch, 2003).