Molecular analysis has revealed the possible existence of Samoana diaphana, previously believed endemic to Moorea, on Tahiti (O'Foighil, pers. comm.).

Samoana diaphana is a tree snail species endemic to Moorea and Tahiti in French Polynesia. This species has an area of occupancy (AOO) of 20 km² and an extent of occurrence (EOO) smaller than 1,000 km². It has been reported from three locations, encompassing five known sites: one site (location) on Moorea, and four sites (two locations) on Tahiti. Its EOO, AOO and extent and quality of its habitat are declining. Thus, this species is assessed as Endangered. Continued biosecurity vigilance is critical to prevent further invasive species establishments in this species' habitat. Surveys to determine the current distribution of this species and population size, status and trends are also recommended, as is site protection and habitat monitoring.

This species is endemic to French Polynesia, where it occurs on Moorea (the type locality) and the neighbouring island of Tahiti. In 2003, it was thought to be extinct (Coote and Loève 2003), but it is now known to survive in five sites: four on Tahiti and one on Moorea. Based on the presence of introduced predatory species, these are considered three locations (two on Tahiti and one on Moorea).

This species was described by Cooke and Crampton (1953) using Moorean specimens collected in 1934 from montane forest habitat (~660 m altitude). Kondo (1973) also listed it as a Moorean endemic, J.B. Burch having collected it on a montane ridge in 1970. However, Johnson et al. (1986) recorded it from a montane site on Tahiti (co-occurring with Samoana burchi) as well as from four Moorean sites: two lower elevation valleys in the northwest of the island where it co-occurred with S. attenuata; and two higher elevation localities in the southeast of the island. After the introduction of Rosy Wolfsnail (Euglandina rosea) in the 1970s, the S. diaphana population declined and was believed to have become extinct (Coote and Loève 2003). However, morphological and molecular diagnoses confirmed that surviving populations occur on two montane sites on Tahiti: Mts. Aorai and Pihaaiateta (Lee et al. 2009). In addition, a photographed montane Moorean individual (380 m elevation on a ridge above Col des 3 Cocotiers) was identified as S. diaphana (Lee et al. 2009). Additional Tahitian survivors were recorded by Trevor Coote in 2010 in two other sites: Mt. Mahutaa (high altitude) and Fautaua Valley (lower altitude, co-occurring with Partula clara).

Its area of occupancy is around 20 km², based on occurrence in these five sites.

The five known site records consist of either a single observed snail or a small cluster of snails. Therefore, the current known population is small.

This is an arboreal species found in rain forest, in both valleys and montane habitats.

The primary threat to this species is from the introduced predatory Rosy Wolfsnail (Euglandina rosea), which was introduced in an attempt to control the introduced crop pest species Achatina fulica (Giant African Snail). Euglandina rosea has extirpated most valley partulid populations since its introduction in 1975 (Tahiti) and 1977 (Moorea) (Coote and Loève 2003, Coote 2007) and extends at least to an altitude of 1,400 m into the montane forests of Tahiti (Lee et al. 2008, 2009; Gargominy 2008). Lower elevation populations are therefore directly exposed to the predator and lower elevation populations on Moorea appear to have been extirpated, with only one record of a surviving montane Moorean population. On Tahiti, there is one known surviving valley population and three known montane populations. It is not clear how serious the threat is for surviving montane Tahitian populations because the predator may be relatively ineffective at these altitudes (Gerlach 1994, Gargominy 2008, Lee et al. 2009). Montane Tahitian habitats are relatively inaccessible and undisturbed; but there is some loss of habitat due to anthropogenic actions, especially fire (Gargominy 2008). The predatory New Guinea Flatworm (Platydemus manokwari) is now present in most of these areas but, like E. rosea, it does not appear to establish permanent populations at higher altitudes.

Many partulids were used in necklace making but no trade was recorded in this species.

No directed conservation efforts are known to be in place for this species. Field work to define the current distribution of this species, as well as research on its population status and trends, is required. Identification of priority sites for species conservation (e.g. key biodiversity areas that include threatened land snails) and reducing the impacts of human activities, and invasive species, are also urgently needed.