An Atlas of Oxfordshire Terrestrial Mollusca

Submitted by Steve Wilkinson on Sun, 09/05/2010 23:55
Reference

S. J. Gregory and J. M. Campbell. 52 pp. Occasional Paper No. 20, published by Oxfordshire Museums in Co-operation with the Northmoor Trust. Available from John Campbell, Oxon BRC, Oxfordshire County Museums Store, Witney Road, Standlake, Oxfordshire, 0X8 7QG.

Review source

Originally reviewed by Geraldine Holyoak in 2001.

Published in Journal of Conchology (2001), Vol.37

The value of mapping local distribution of snails by tetrads (2x2 km grid squares) has been shown by the published studies of the Isle of Wight (R. C. Preece) and Suffolk (I. J. Killeen). This Atlas is a worthy successor that records the distribution of land Mollusca in modem Oxfordshire (which comprises VC23, the 'old' Oxfordshire, plus part of VC22, north-western Berkshire). Like the earlier studies, it provides a more detailed picture of species' distribution than the national Atlas maps, allowing closer study of changes in status and the relationship between distribution patterns, geology and habitat types.

A coverage map at the beginning indicates that all but a handful of the tetrads were surveyed, and a total of more than 20 000 records was accumulated (unfortunately the map lacks a legend, so the actual number of species found in each tetrad is unclear). The thoroughness of geographical coverage is a substantial achievement, well justifying publication of this comprehensive check-list and set of distribution maps for Oxfordshire. Besides the two authors, Dr Arthur Spriggs is acknowledged as having contributed many of the records.

Coverage for most of the snails is evidently fairly comprehensive and complete enough to enable the authors to comment briefly on ecological and historical aspects of their distribution patterns. Indeed, the numerous records for such tiny snails as Punctum pygmaeum and Carychium shows the high quality of the survey work. Those involved in field recording will appreciate the sustained effort required to produce such good cover- age, but we are unfortunately told little in the Atlas about the field methods used and recording strategy adopted. It is evident that slugs have been less comprehensively recorded, especially some recent segregates in the genus Arion, and the lack of dissections to check Succinea putris and Oxyloma pfeifferi is noted by the authors.

With 91 species known, Oxfordshire is one of the richer counties for landsnails and slugs. It is pleasing to see from the tetrad maps that such rarities as Ena montana, Umax cinereoniger and Malacolimax tenellus maintain strong populations in its woodlands. However, the maps show conspicuous declines of a few native species, most notably Helicigona lapicida and Helicella itala, whereas some introduced species have become widespread in the county, notably Boettgerilla pollens.

Overall, this modest publication provides a good record of the distribution of Oxfordshire land Mollusca. It seems a pity that the authors did not also include freshwater Mollusca, but this should not detract from the thorough coverage and careful recording evident in this Atlas.