Land Snails from Mothe, Lakemba, and Karoni Islands, Lau Archipelago, FijP

Land snails sorted from bagged leaf litter on Karoni, Lakemba, and Mothe Islands in the Lau Archipelago of Fiji numbered 35 species. Literature and Field Museum of Natural History collection records add four others for a total of39 species. There are now 13 recorded from Mothe, 20 from Karoni, and 22 from Lakemba. Nine of these taxa are introductions from outside the Pacific basin, dating from European commercial activities; three probably were introduced by Polynesian voyagers; and 27 probably are endemic to Lau. Many of the latter belong to widely distributed Pacific basin species complexes and cannot be assigned a specific name with certainty, but several are restricted to just one or two islands in Lau. The diversity of species on each island does not follow the species-area curve. THROUGH THE COURTESY of Walter O. Cernohorsky of the Auckland Institute and Museum, it was possible to study land snails from Karoni, Lakemba, and Mothe Islands in the Lau Archipelago. These samples were made by Cernohorsky during the Royal Society of New Zealand Pacific Expedition in late June and early July 1977. The collections were obtained by filling one (Mothe) or two bags (Lakemba and Karoni) with leaf litter, then hand sorting back at camp in the evenings. It took approximately I hr collecting time to fill two bags. A few specimens were collected from tree trunks, and a very few empty shells of arboreal species were sorted from the litter, but undoubtedly there is underrepresentation of the treedwelling species. The specimens are deposited in the Auckland Institute and Museum, with some duplicates in the Field Museum of Natural History. Catalog numbers of the latter (preceded by FMNH) are included for reference. The collection from Karoni (179°32' E, 18°45' S) was made on 4 July 1977. Karoni 1 Manuscript received 10 December 1977. 2 Field Museum of Natural History, Department of Zoology, Roosevelt Road at Lake Shore Drive, Chicago, Illinois 60605. 39 is a highly dissected island of less than half mile diameter, located just southeast of Mothe and within the same reef complex. The collection from Lakemba (179°13' E, 18°13' S) was made during an 8-day period at various times from 24 to 30 June 1977. This volcanic island is 22 sq mi. The collection from Mothe (179°30' E, 18°41' S) was taken on 7 July 1977. Mothe is also a volcanic island, but it is only 4 sq mi. The main emphasis was on marine collecting, and the land snails were obtained as a byproduct. The 35 species included in these collections provide a number of new records for both the particular islands and Lau Archipelago, but perhaps more importantly serve to emphasize several facts. First, the collecting effort in many of the Pacific Island groups is still less than adequate. Second; for many genera it is impossible to assign meaningful specific names, as the groups have not been revised in this century. Third, a dynamic pattern of colonization by, and replacement of, introduced species of land snails exists on many Pacific Islands, and periodic collections to monitor the changes are needed. Fourth, the observed diversity of land snail species on small islands does not follow the species-area curve or McArthur-Wilson colonization-extinction model.