Partula tree snails used to be found on islands across the Pacific Ocean, from New Guinea to Polynesia. Although they were familiar species to the Polynesian inhabitants of the islands, who used to make necklaces out of their multi-coloured shells, they were first brought to the attention of scientists in 1769. In that year the first specimen of Partula faba was collected on Captain Cook's first expedition to the Pacific. Some 150 species were described and those of French Polynesia became important in the study of evolution. They were among the first animals to be investigated in the wild for evidence of speciation in action, first with the studies of Alfred Meyer in 1899, then Henry Crampton in 1906-56 and finally the geneticists Bryan Clarke, Jim Murray and Michael Johnson from the early 1960s. This research came to an abrupt end in 1987 when most of the species disappeared (as Jim Murray reported in that year).
In the 1970s and early 1980s the carnivorous snail Euglandina rosea was introduced in a catastrophic biological control programme. Euglandina ignored its intended target, the large and tough giant African snail Lissachatina/Achatina fulica and instead devoured the small and tender Partula snails. As a result at least 50 species of Partula are now completely extinct, a further 11 survive only in captivity and just 5 species still exist in the wild in French Polynesia. The captive breeding programme for the surviving species has been in place since the early 1990s and many species have existed only in small boxes in controlled conditions for many generations. Efforts are underway to find a way of returning them to the wild. This requires new approaches to conservation and reintroduction as there is no realistic prospect of eliminating Euglandina. Instead, we must find a way of enabling Partula to coexist with its introduced enemy.
As Partula disappeared their place as exemplars of species radiations was taken by other species groups that have now become classics of evolutionary research, such as the Galapagos finches, African cichlid fish and Caribbean anole lizards. However, Partula remain an exceptional research group due to their sheer range and diversity: around 150 species spread over 40 islands in over a million square kilometers of ocean.
Compiled by Justin Gerlach: contact
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