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Samoana abbreviata

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA MOLLUSCA GASTROPODA STYLOMMATOPHORA PARTULIDAE

Scientific Name: Samoana abbreviata
Species Authority: (Mousson, 1869)
Common Name/s:
English Short Samoan Tree Snail
Taxonomic Notes: This species seems closely related to Samoana conica, but its shells are dextral, whereas those of S. conica are sinistral. Its shell is generally yellowish -green in colour. Least common of the three Tutuila partulids.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B2ab(iii) ver 3.1
Year Published: 2012
Date Assessed: 2011-09-13
Assessor/s: Cowie, R.
Reviewer/s: Barker, G., Triantis, K., García, N. & Pippard, H.
Justification:
This species is currently known only from a single location within an area of occupancy of less than 5 km2, and a very small known population (15 specimens recorded in 1998). Therefore the population is considered to be declining, as is its quality of habitat due to the introduction of E. rosea. It is therefore listed as Critically 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 its population size, status and trends are also recommended, as is site and species protection in American Samoa.

History:
2000 Critically Endangered
1996 Data Deficient
1994 Extinct (Groombridge 1994)
1990 Indeterminate (IUCN 1990)
1988 Indeterminate (IUCN Conservation Monitoring Centre 1988)
1986 Indeterminate (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description: This is a single island endemic that occurs in American Samoa on the island of Tutuila, at the following localities: Alava/Maugaloa ridge, Faiga ridge and along the Vatia powerline trail, Toa ridge. In addition, empty shells have been found on Pagatatua ridge, Levaga ridge and Polauta ridge. The estimated area of occupancy is approximately less than 5 km2 (Cowie and Cook 1999).
Countries:
Native:
American Samoa (American Samoa)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This is the least common of the three Tutuila partulids. It is considered very rare and current population trends are unknown, although there is evidence for historical decline (Cowie and Cook 2001). The Bishop Museum malacological collection database lists 139 collections of this species made in 1926 and 1930 from many localities spread across Tutuila; some of these collections including numerous specimens. Clearly it was widespread and in some places abundant. Subsequently, however, until the 1998 survey, it had not been seen alive since 1940.

In a 1998 survey (Cowie and Cook 1999), a total of eight live individuals was seen at seven of the quantitative survey stations. Three of these stations were on Alava/Maugaloa ridge; one each were at mid-elevations on Faiga ridge and along the Vatia powerline trail; and two were on Toa ridge. Single empty shells were collected at each of two additional stations on Maugaloa ridge, and one each on Pagatatua ridge, Levaga ridge and Polauta ridge. Five additional live individuals were seen at five points along the Alava/Maugaloa ridge trail; one was seen high on Toa ridge; and one was seen on Polauta ridge. Therefore, a total of 15 live individuals was seen. Its distribution strongly mimics those of Eua zebrina and Samoana conica with a concentration in the central area from Toa ridge to the Vatia powerline trail and along Alava/Maugaloa ridge in this area. Finding Samoana abbreviata alive is of major significance, but it is clearly surviving in extremely low numbers.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This is an arboreal species from moist forest from near the coast to crest of ridge.
Systems: Terrestrial

Threats [top]

Major Threat(s): The main threats to this species are habitat modification and destruction resulting from the impacts of invasive species (e.g. exotic plants) and agricultural activities and encroaching settlements. In addition, the species is particularly threatened by the introduction of the predatory snail E. rosea.

Conservation Actions [top]

Conservation Actions: The entire known distribution of the species is in the National Park of American Samoa (Tutuili section).  However, there are no species-specific management actions in place to control the current threats to the species. As eradication of E. rosea isn't likely to be possible, captive breeding and species monitoring is highly recommended. Establishing miniature preserves (enclosures) that exclude E. rosea is also recommended.
Citation: Cowie, R. 2012. Samoana abbreviata. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 21 April 2014.
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