Diplommatina ringens


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Diplommatina ringens
Species Authority: (Crosse, 1866)
Palaina ringens Crosse, 1866

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii)+2ab(iii) ver 3.1
Year Published: 2012
Date Assessed: 2011-08-22
Assessor(s): Rundell, R.J. & Cowie, R.
Reviewer(s): Barker, G., Triantis, K., García, N. & Pippard, H.

This is a single-island endemic restricted to the island of Peleliu in Palau. The species is listed as Critically Endangered due to its small area of occupancy, a single location, and the known current decline in extent and quality of its habitat, due to deforestation and the impact of invasive species. Continued biosecurity vigilance is critical to prevent invasive species establishments in this species' habitat. Surveys to determine the current distribution of this species and its population size, status and trends are also recommended.

1996 Data Deficient
1994 Vulnerable (Groombridge 1994)

Geographic Range [top]

Range Description:

This is a single-island endemic restricted to the island of Peleliu (Beliliou) in Palau. The species was collected at only 6 sites (1 location) on Peleliu (12 km2) in 2003 (Rundell 2005). It inhabits the native forest of the “Bloody Nose Ridge” area of this island (Rundell 2005) and thus its area of occupancy is estimated to be approximately 4 km2.

Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: There is no information on population size or trends.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: This species is found primarily on the ground in limestone karst in tropical moist lowland forest.
Systems: Terrestrial

Use and Trade [top]

Use and Trade: This species is not utilized.

Threats [top]

Major Threat(s):

This species is threatened by destruction and modification of its native forest habitat. This species was apparently able to survive the burning of much of the forest during World War II (Hinz 1995, Crombie and Pregill 1999), however review of additional data from museum collections is needed to better understand how widespread the species was before WWII (e.g. based on the 1936 collections of Y. Kondo at the Bishop Museum in Hawaii), and whether the species has declined in the interim period. It is possible that the species was able to survive the substantial vegetation destruction and changes of WWII (Crombie and Pregill 1999) because it is found primarily on the ground in limestone karst, and was therefore able to hide deep in moist crevices while vegetation returned to the island (e.g. as might occur in the Rock Islands of Belau during temporary drought periods; Colin 2009). This phenomenon is distinct from irreversible habitat change events (e.g. building a hotel on or near the limestone karst forest), from which most Palau species with similarly restricted ranges could not recover. The localities where this species occurs are low elevation areas near permanent human habitation and are susceptible to land alteration for developments.

Rats such as Rattus norvegicus (Norway Rat), Rattus rattus (Ship Rat), and Rattus exulans (Polynesian Rat) represent a threat to the species. These species can be introduced and repeatedly re-introduced (by boat) by humans, but can also cross water independently. There are no known indigenous predatory land snails in Palau, and indigenous Palau species have evolved in the absence of such predation pressures. Euglandina rosea (Spiraxidae), Gonaxis kibweziensis and Gulella bicolor (Streptaxidae) have been introduced to Palau within the past 100 years (Cowie et al. 1996), and throughout the Pacific. Euglandina rosea and Gonaxis spp. in particular have been introduced in ill-conceived attempts at biocontrol for Achatina fulica (Meyer et al. 2008). Of these non-indigenous predatory species, Gulella bicolor was found by Cowie (Cowie et al. 1996) and Rundell (R.J. Rundell unpublished data, 2003, 2005, 2007).  Although Euglandina rosea was not found, the presence of Achatina fulica (an agricultural pest) in Palau, particularly on the islands of Koror and Babeldaob (R.J. Rundell unpublished data, 2003, 2005, 2007) means that agricultural areas on these islands (e.g. Airai State) may be subject to renewed biocontrol attempts in the future, and vigilance is necessary regarding the potentially devastating consequences of E. rosea re-introductions. Note that accidental introductions (and distribution to different localities) are likely, as a result of transportation of soil and organic debris (where snail eggs may be present), plants and produce.

Conservation Actions [top]

Conservation Actions:

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, especially on the small islands, is also urgently needed. Biosecurity vigilance to prevent the establishment of invasive species is crucial. The Palau Conservation Society has been supportive of recent land snail survey work in Palau.

Citation: Rundell, R.J. & Cowie, R. 2012. Diplommatina ringens. The IUCN Red List of Threatened Species. Version 2014.2. <>. Downloaded on 25 July 2014.
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