Land molluscs on the Isles of Scilly: species richness and composition related to area

Variation in the species richness and composition of land mollusc faunas from seven islands in the Isles of Scilly is analysed in relation to island area and human activity. Comparisons are made with other island faunas, and with those from appropriate areas of mainland Britain. Whereas the faunas of the largest and most heavily populated island, St. Mary's, and of the archipelago as a whole, are as rich as those found in the same areas of mainland, the smaller islands are species-poor, and conform to the species/area relationship normally found amongst islands. The islands' faunas are heavily influenced by human activity; introduced species are numerous, but native woodland and wetland specialists are few. Comparisons with other islands and areas of mainland reinforce these conclusions.