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Glabrennea thomasseti

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA MOLLUSCA GASTROPODA STYLOMMATOPHORA STREPTAXIDAE

Scientific Name: Glabrennea thomasseti
Species Authority: (Sykes, 1909)
Synonym(s):
Gulella thomasseti (Sykes, 1909)
Taxonomic Notes: Originally described as Ennea thomasseti Sykes, 1909. Placed into Gulella by Connolly (1925) and Germain (1934). A recent revision provisionally placed this into Gulella, but noted that it may be a distinct genus (Gerlach and Bruggen 1999), along with 'G.' gardineri and 'G.' silhouettensis. This species has now changed genus, along with 'G.' gardineri and 'G.' silhouettensis, from Gulella to Glabrennea (Schileyko 2000).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii,v)+2ab(iii,v) ver 3.1
Year Published: 2009
Date Assessed: 2006-01-11
Assessor(s): Gerlach, J.
Reviewer(s): Pollock, C.M., Miller, R.M. & Seddon, M.
Justification:
This species has a restricted extent of occurrence (estimated at 80 km²) and area of occupancy (estimated at 0.01 km²), comprises two isolated populations, and faces ongoing deterioration in habitat quality due to the spead of invasive plants. Since 1905, the original location of this species (Cascade Estate, Mahé) was largely cleared for cinnamon (Cinnamomum verum) plantations and the remaining native forest was invaded by cinnamon and other invasive plants, which are now dominant. Searches of the area and nearby forest failed to locate G. thomasseti and it was subsequently assessed as Extinct in 1996. In August 2002, a single fresh shell of G. thomasseti was found in an a relict fragment of primary forest approximately 1.8 km south-south-east of the original collection site. This specimen confirms the continued survival of the species and suggests that the species is restricted to primary forest habitat. A specimen collected from mist forest at Congo Rouge in 1994 was subsequently identified. The species is currently known from two relict primary forest patches: 40 m² of Vateriopsis seychellarum forest at Grand Bois and 100 m² of mist forest at Congo Rouge. The extent of occurrence for this species is currently estimated at less than 100 km² and the area of occupancy at less than 10 km², with only 1 location comprising two isolated populations and continuing decline in quality of habitat (as indicated by invading cinnamon saplings). A continuing decline in the number of mature individuals may be occurring. Therefore it is assessed as Critically Endangered under criterion B (CR B1ab(iii,v)+2ab(iii,v)).
History:
2003 Critically Endangered (IUCN 2003)
2003 Critically Endangered
1996 Extinct
1994 Extinct

Geographic Range [top]

Range Description: This species is endemic to the Seychelles (Mahé island), with an extent of occurrence (EOO) of 80 km² and an area of occupancy (AOO) of 0.01 km². It was originally known from Cascade Estate on Mahé island, Seychelles (Sykes 1909). The species was thought to have been lost after high altitude forest habitat in the area was cleared for cinnamon plantations. However, the species was rediscovered in 2002 in Grand Bois, Mahé. It is also found in mist forest at Congo Rouge, Mahé.
Countries:
Native:
Seychelles (Seychelles (main island group))
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In 2005, the population was estimated to be less than 1,000 individuals.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: The type specimen was collected from "mountain forest" (Sykes 1909). The rediscovered specimen was collected from leaf litter in a relict fragment of primary forest (Gerlach 2002); it is now known from mist forest. It is thought that the species is restricted to primary forest habitat. A tropical forest species, this snail is predatory on small invertebrates.
Systems: Terrestrial

Threats [top]

Major Threat(s): Currently, the main threat to the species is habitat degradation caused by invasive cinnamon trees (Cinnamomum verum). Small-holder farming and small-holder wood plantations caused habitat deterioration in the past, but these threats have since ceased.

Conservation Actions [top]

Conservation Actions: Present in the Morne Seychellois National Park. The preservation of the primary forest habitat at Grand Bois, dominated by Vateriopsis seychellarum, and prevention of further invasion by alien plant species is imperative for the survival of G. thomasseti (Gerlach 2002).

Citation: Gerlach, J. 2009. Glabrennea thomasseti. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 22 October 2014.
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