Partulidae

Abstract: The broad outline of the systematics of the endemic Pacific island land snail family Partulidae has been understood for some time. The family is divided into three genera: Eua has four species, confined to Tonga and Samoa; Samoana has about 23 species, widely but sporadically distributed in Polynesia and the Mariana Islands; Partula has about 100 species, distributed from Belau to the Society Islands. This review integrates this systematic and biogeographic knowledge with work on ecology, population genetics and speciation that has concentrated especially on the recently speciated Partula spp. of Moorea in the Society Islands. Explanations of Moorean diversity (much of which seems unrelated to ecological factors) based on parapatric speciation and the evolution of morph ratio clines in the absence of isolation have predominated, although without incontrovertible support. Unitary explanations are probably not appropriate. Rather little is known of the basic biology of partulids. They are generally arboreal; feed on a wide range of partially decayed and living plant material; and are relatively long-lived, slow reproducing, ovoviviparous, cross- or self-fertilizing hermaphrodites. The phylogenetic and geographical origins of the three genera are unknown. Partula may have evolved, somewhere unknown, from Samoana, which evolved from Eua in the Tonga-Samoa region, this being the region of origin of Eua; but the opposite sequence has also been postulated. The question is unresolved. Origins of the Moorean species are better understood as their inter-relationships are relatively clear. Rather few dispersal events probably took place and the Society Island fauna as a whole may be derived from but two colonization events - first by a Samoana sp. and later by a Partula sp., both of which then speciated in situ - with a few intra-archipelago colonization events taking place subsequently, predominantly in a southwesterly direction from the older to the younger islands. Many of the questions posed by the group may never be answered. Some species, notably those of Moorea, are already extinct in the wild; others are severely threatened. Artificial introductions of both plants and animals, combined with urban and agricultural development, have had significant impacts, but ill-conceived biological control programmes, targeted at the Giant African Snail, Achatina fulica, constitute currently the most serious threat. However, significant areas are still open to research. Analysis of DNA variation, combined with modern ideas of Pacific biogeography, should allow the whole range from the broad origins of the fauna to the detailed evolution within groups of species to be addressed. Some species may yet be relatively secure in the wild and allow field studies, but extraction of DNA from museum specimens provides an exciting opportunity to continue unravelling the evolutionary history of these endangered snails and to contribute further to our understanding of evolutionary processes and the biogeography of the Pacific.

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

Abstract: Recent literature abounds with reports of the decline and extinction of the endemic species of Achatinellidae and Partulidae in the Hawaiian and Society Islands, respectively, resulting from the introduction of the predatory snail Euglandina rosea. Here, we describe a previously unrecognised radiation of helicinid land snails from the Gambier Islands of French Polynesia, with up to seven species co-occurring in a single locality and up to eight species on a single island. This radiation had already become extinct (nine of ten species) several decades before the expansion of E. rosea in the Pacific, and even before the species were collected for scientific study. The Gambier Islands case study shows that massive extinctions of endemic land snails had already taken place in the nineteenth century, but have remained largely unrecognised and undocumented. Nine of the ten species are new to science and are described here almost entirely based on empty shells collected from the shell bank of the soil after the extinction had already taken place. This helicinid radiation alone increases the number of documented global mollusc extinctions by almost 2 %. Most of the species are minute and, at 1.5 mm, rank among the smallest, if not the smallest, species in the family. Several have apertural barriers and one has opercular apophyses—character states not previously documented in Pacific helicinids. Whereas the only surviving Gambier species belongs anatomically to the genus Sturanya, representative helicinid species from the Austral, Society and Cook Islands are not congeneric with it, and the generic name Nesiocina is here established for the latter taxa. It is hypothesised that the extinct Gambier species were also Nesiocina.

Abstract: Four partulid tree snail species are known from American Samoa. In 1998, we surveyed the recently established National Park (units on three islands: Tutuila, Tau, Ofu) and neighboring areas for partulids. On Tutuila, Samoana abbreviata, previously considered probably extinct, was extremely rare (15 snails seen); Samoana conica was more common (288 snails) but still rare; Eua zebrina was the most common (1102 snails), at one locality perhaps near its natural abundance. The species have similar distributions within the Park. All three have declined dramatically since the 1920s. Before 1980, when the predatory snail Euglandina rosea was introduced, habitat destruction, and perhaps rat predation and shell collecting, probably caused the decline. The Park provides protection to the Tutuila partulids by protecting habitat, although development is still a potential problem. But predation by E. rosea may yet cause their extinction. On Ofu (only outside the Park), 12 live Samoana thurstoni were found; 31 have now been recorded by western science. Also, an apparently robust population of E. zebrina, previously considered a Tutuila endemic, was found. Euglandina rosea is not on Ofu, so these populations are important remnants of the fauna. No partulids were found on Tau; none has ever been recorded there.