Sinployea rotumana

[surroundx]

Cowie, Robert H., Régnier, Claire, Fontaine, Benoît, and Bouchet, Philippe. (2017). Measuring the Sixth Extinction: what do mollusks tell us? The Nautilus 131(1): 3-41.

[koeiyabe]

This species is known from Rotuma (43.7 km2) and Hauatia (~0.01 km2) islands in the Rotuma Group in Fiji. The species was described (Smith 1897) on the basis of at least 6 specimens from unspecified location(s) on Rotuma Island (syntypes NHMUK 1897.11.8.57-63). The Rotuma Island record from 1897 is not supported by any additional locality information. The Hauatia Island record is based on a single specimen collected in 1938. A brief survey of land snails during a Fiji government marine resources survey in mid-1986 (Parkinson 1988) did not yield the species. Thus there is no information on current geographic range of the species. If it is assumed the species is potentially distributed throughout the Rotuma Group (i.e. presence on Solkope, Hatana and Hofliua islands in addition to Rotuma and Hauatia), the estimated EOO is ~45 km2. The present area of occupancy cannot be determined as the species has not been surveyed since 1938, but potentially it is in the order of 9.8 km2 if widely distributed but extirpated from 80% of Rotuma Island. However, if the species is now restricted to Hauatia Island, the area of occupancy is estimated as less than 0.01 km2.

The species was last surveyed in 1938, so no recent information is available on area of occupancy. On Rotuma Island which constitutes the large part of the area of extent of the species, there has been considerable loss and modification of the forests over the past few centuries. Likely suitable habitat remains over about 20% of Rotuma Island (patchily distributed in areas inaccessible and unproductive, such as sea cliffs and interior rock rubble). Fijian census data indicate that while there has been a considerable increase in the Rotuman human population over the past century, the majority of Rotumans live in mainland Fiji. The population on Rotuma has been relatively stable over that period and indeed, the current human population is possibly lower than prior to arrival of Europeans in the Pacific. These trends suggest a new equilibrium may have been reached between human extractive uses of the land and natural regenerative processes. There is circumstantial evidence for the present condition of the vegetation and thus snail habitat having considerably improved since J.S. Gardiner (in Smith 1897) reported “There is no indigenous forest left anywhere on the island”. The islands of Hauatia, Solkope, Uea, Hatana and Hofliua have suffered minimal human disturbance and evidently have more-or-less intact indigenous vegetation cover. In the absence of information on local extinctions due to other factors such as predation by invasive species, the species is inferred to be maintaining its area of occupancy. It should be noted however, that other Sinployea species have exhibited declines, and extinctions, on other Pacific islands (Solem 1983; Brook 2010).

www.iucnredlist.org/species/195600/177158523#geographic-range