Modern land mollusc communities from Flat Holm, South Glamorgan

Modern land molluscan communities on the island of Flat Hoim in the Bristol Channel are described. Most are from grassland which has been disturbed by breeding gulls and human activity. There are three main molluscan species which favour unstable habitats, and eighteen others, and cluster analysis suggests the existence of five groups or communities. For the main areas of grassland, there appears to be little correlation between the communities and habitat factors. It is suggested that the different communities reflect the generally unstable nature of the island’s environment. Comparison with grasslands further east in Britain shows a paucity on Flat HoIm of the more traditional xerophiles, and the significance of this in the use of subfossil assemblages for environmental reconstruction is indicated.