Understanding effect of introduced species to native land snail fauna in the Daito Islands, and establishment of breeding methods for conservation of these endemic snails ―Group for Conservation of Endemic Land Snails of the Daito Islands―

Abstract

Prior studies indicated that the native fauna of land snails in the oceanic Daito Islands has been decreasing since introducing the alien invasive species. However, the effects of introduced predators Pheidole megacephala and Geonemertes pelaensis were ignored in such studies. Under these circumstances, to clarify such effects to native land snails of the islands, we conducted investigation for distribution areas of these two invasive predators in the islands, including coastal area, which was insufficient in the previous studies. In addition, we also tried breeding of some endemic land snails of the islands for establishment of breeding methods and keeping the colony in the lab. Our results indicated that the P. megacephala decreased individual numbers of micro snails. However, the G. pelaensis did not occur any negative effect to the land snails. Compared with the Daito Islands, these invasive predators showed similar results to its native fauna of the snails in the continental Okinawa Island. Under the laboratory condition, we succeeded in breeding Zaptyx daitojimana, but not for the genus Nesiohelix. Further analyses and development of breeding methods are needed for conservation of terrestrial molluscs fauna of the Daito Islands