The deliberate introduction of the rosy wolf snail Euglandina rosea to the Society Islands in the 1970s led to the mass extirpation of its rich Partulidae (Pilsbry, 1900) fauna, comprising approximately half of all species in this Pacific island tree snail family. On Tahiti ongoing field surveys have documented the survival of two of seven endemic species of Partula (P. hyalina and/or P. clara) in 38 valleys. E. rosea is now a potent extinction agent across Oceania and determining the factors enabling these two taxa to endure may have wide conservation import. We hypothesized that P. hyalina and P. clara have survived because they were the most abundant and/or widespread species and that they will eventually become extinct. We lack demographic data contemporaneous with predator introduction, but an early 20th century study by H.E. Crampton provides historical demographic data for intact Tahitian partulid populations. Crampton found that P. clara and P. hyalina, although widespread, were consistently rarer than their now-extirpated congeners, including in the 23 valleys he surveyed that retain surviving populations. Given this result, and the recent finding that P. clara and P. hyalina comprise a discrete founding lineage in Tahiti, it is plausible that some shared biological attribute(s) may have contributed to their survival. Crampton recorded the clutch sizes of thousands of gravid Tahitian partulids and found that these two taxa had higher instantaneous mean clutch sizes than did co-occurring congeners. Higher fecundities may have contributed to the survival of P. hyalina and P. clara in the valleys of Tahiti.

Les longues séries temporelles d'observation de la radioactivité dans l'atmosphère (au niveau du sol) permettent d'étudier l'évolution de ce réservoir après les injections des expérimentations nucléaires militaires, de l'activité industrielle, ou suite aux accidents tel que celui de Tchernobyl (1986). Conjointement à l'observation des radionucléides d'origine artificielle, les radionucléides formés par l'interaction du rayonnement cosmique dans la haute atmosphère, comme 7Be, sont quantifiés. La corrélation entre les composantes naturelles et artificielles permet de mieux comprendre l'évolution globale de la radioactivité dans l'atmosphère. L'observatoire de la radioactivité dans l'atmosphère de l'Institut de radioprotection et de sûreté nucléaire (IRSN) a débuté en 1959. Actuellement les aérosols sont prélevés dans 6 stations localisées en Métropole et dans 2 stations en Outre-mer (hémisphère sud). Les concentrations de 137Cs dans les aérosols en 2002 sont de l'ordre de 0,4 μBq m-3 en métropole et 10 fois moins à Tahiti. Les activités du 7Be, de l'ordre de 3 200 μBq m-3, sont similaires en métropole et à Tahiti.

The current distribution of endemic partulid snails on Tahiti in French Polynesia reflects the danger of ignoring expert advice and introducing an alien species into a fragile island ecosystem. The endemic tree-snail fauna of the island now faces extinction. Although the extinction of the native species of Partula (Partulidae; Polynesian tree snails) on Moorea in French Polynesia is well known in the world of conservation biology, losses on other Pacific islands are less well described. This paper presents an update on the status of partulid snail populations on Tahiti in the light of fieldwork undertaken between 1995 and 1997. Native snails still exist in good numbers in two areas, at opposite ends of the island. In other areas, sightings of single or a few individuals indicate remnant populations now on the edge of extinction. Efforts to protect these populations and others in French Polynesia are being planned in collaboration with local government authorities.