An atlas of the non-marine Mollusca of the Isle of Wight

This atlas is the first to show molluscan distributions by tetrads (2x2 kilometre grid squares), an approach pioneered by the botanists. About 120 tetrads cover the Isle of Wight. Although the smallest English county, it is unusually varied in its geology and physiography and detailed mapping was therefore expected to reveal interesting relationships, obscured by the relatively coarse units (10 km squares) used in the national Atlas. This has indeed proved to be the case.

The work includes (a) an introduction describing the geology, physical features, climate and vegetation of the island, accompanied by maps showing these factors; (b) a history of research on the Mollusca from 1860 onwards; (c) the recording strategy adopted by the author; (d) changes in the molluscan fauna; and (e) critical notes on selected taxa. There is a bibliography and an index. The distribution maps, very clearly printed at eight to a page, distinguish old (pre-1950) from recent records. Though much early information, both published and unpublished, has been incorporated, the great bulk of the tetrad records (over 4,000) were gathered in an intensive field campaign in 1978-79. The maps have two unusual virtues. First, since a deliberate effort was made to cover the whole island evenly, without strong bias towards potentially rich or poor tetrads, the resulting patterns may be accepted as showing real distributions. Secondly, the brevity of the recording campaign means that we are offered a quite exceptional picture of animal populations virtually within a single season. This is clearly of great importance for the monitoring of future change. And changes are certainly occurring. For example, it is alarming to notice that the old calcareous grassland species Helicella itala may well be extinct in the island: though past records exist at numerous places, only occasional dead shells can be found. Conversely, several species, mostly those favoured by waste ground and gardens, are spreading. The value for conservation purposes of such precise knowledge is evident. Many of the maps also raise interesting questions about habitat requirements and about interrelationships between species (note, for example, the curiously different distributions of the two Cepaea species).

The atlas is attractively printed and is in every way a model of its kind. Indeed it is the sort of publication which it is hoped other regional biological record centres will emulate.