Samoana diaphana

This species was described by Cooke & Crampton (1953) using diagnostic conchological features.  Its taxonomic validity has been independently corroborated using allozyme (Johnson et al. 1986) and mitochondrial DNA (Lee et al. 2009) phylogenetic analyses.

This species is endemic to French Polynesia and is found on Moorea (type locality) and also the neighboring island of Tahiti. It was thought to be extinct (Coote and Loève 2003), but it is now known to survive in four Tahitian and one Moorean localities (two and one locations, respectively).

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 4 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.

Surviving populations were confirmed using morphological and molecular diagnoses to 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 a surviving 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).

Considering that the species is known from five sites, the inferred area of occupancy is 20 km².

The primary threat is posed by the introduced predatory land snail Euglandina rosea.  The predator 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 1400 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 action, especially fire (Gargominy 2008).