From 61 species to five: endemic tree snails of the Society Islands fall prey to an ill-judged biological control programme

Abstract

Following the well documented extinctions of many species of endemic tree snail (family Partulidae) throughout French Polynesia, field surveys were undertaken on four islands in the Society archipelago to provide up to date information for the international conservation programme for this group of invertebrates. These surveys have confirmed the loss of all species of Partula in the wild on the Society Islands other than Tahiti. Thirty-three species have been lost from Raiatea, thereby eliminating one of the most outstanding examples of island evolutionary radiation. On Huahine the disappearance of P. varia and P. rosea, used for making lei (shell jewellery), had an economic and social effect on the local community: many of the women of the villages lost their livelihoods, and the artisan's association folded. The seven species of Partula on Moorea were extinct in the wild by the mid 1980s, terminating almost 100 years of biological research. It now seems that the remnant populations of Samoana attenuata discovered only 5 years ago are the only species of partulid still surviving beyond Tahiti on the Society Island group. The mixed species populations in the Te Pari area of Tahiti-Iti are still extant, but the predatory snail Euglandina rosea has now spread to the last valley on the Peninsula that did not have previous evidence of predator activity. On Tahiti-Nui populations of partulid, without the predator, were found near the crest of Mount Tahiti above Orofero Valley. Partulidae are clearly a highly threatened family of invertebrates, and in need of the most intense conservation focus.