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Geomitra grabhami 

Scope: Global & Europe
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Gastropoda Stylommatophora Hygromiidae

Scientific Name: Geomitra grabhami (Wollaston, 1878)
Synonym(s):
Helix grabhami Wollaston, 1878
Taxonomic Source(s): Bank, R.A. and Neubert, E. 2017. MolluscaBase. Checklist of the land and freshwater Gastropoda of Europe. Last update: July 16th, 2017.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii)+2ab(iii) ver 3.1
Year Published: 2018
Date Assessed: 2016-12-02
Assessor(s): Teixeira, D., Cameron, R., Groh, K. & Seddon, M.B.
Reviewer(s): Neubert, E. & Allen, D.J.
Justification:
This species is endemic to Deserta Grande Island in the Madeira Archipelago. The species was known from the northern end of the island, where it was recorded as recent shells by Groh and Hemmen (1986), but it was not refound by Cameron and Cook (1999). However the species was recently found living at a new locality, Fajã Grande, on the eastern coast of the island by Teixeira and Silva in 2008 and again by Teixeira and Isamberto when resurveyed in 2013. The species is found on a coastal plateau formed by the collapse of coastal cliffs, where there is a threat of further landslide and erosion. There is also a threat from predation from mice, which have not been eradicated yet, and there is an increase in the frequency of droughts, which impacts both the species as well as adding to ground instability. The species is assessed Critically Endangered (CR(B1ab(iii)+2ab(iii)) based on single location with an assumed small population with ongoing threats.

There is a Life Project survey work ongoing to monitor the status of this species and a species conservation action plan is planned for 2019. The species should be reassessed if future fieldwork refinds the species at the original locality at the northern end of the island, or finds further new localities.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to the Madeira Archipelago, where it is known from subfossil records in the Castanheira Valley at the northern end of Deserta Grande (Groh and Hemmen 1986). The species was not refound by Cameron and Cook (1999), however live specimens were found in 2008 by Teixeira and Silva at Fajã Grande on the eastern coast of Deserta Grande and again in 2013 (Teixeira and Isamberto; D. Teixeira pers. comm. 2016).
Countries occurrence:
Native:
Portugal (Madeira)
Additional data:
Estimated area of occupancy (AOO) - km2:4Continuing decline in area of occupancy (AOO):Unknown
Estimated extent of occurrence (EOO) - km2:4
Continuing decline in extent of occurrence (EOO):Unknown
Number of Locations:1
Lower elevation limit (metres):10
Upper elevation limit (metres):20
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The species was originally considered extinct by Waldén (1983), although recent shells were found in the Castanheira Valley in 1986 (Groh and Hemmen 1986). The species was found at the new locality at Fajã Grande on the eastern coast of Deserta Grandebby Teixeira in 2008 and again in 2013 (D. Teixeira pers. comm. 2016). There are no data on population size or trend, however there are likely to be a very small number of specimens (less than 500 mature individuals).
Current Population Trend:Unknown
Additional data:
Number of mature individuals:400-500Continuing decline of mature individuals:Unknown
Extreme fluctuations:UnknownPopulation severely fragmented:No
All individuals in one subpopulation:Yes

Habitat and Ecology [top]

Habitat and Ecology:This species was originally described as living among lichens growing on rocks (Seddon 2008). At the currently known location at Fajã Grande, the species is found amongst large boulders on a plateau area formed by a large landslide and erosion below steep cliffs, c.15 m Asl (D. Teixeira pers. comm. 2016).
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: The species is occasionally sold by shell collectors.

Threats [top]

Major Threat(s): Currently overgrazing by introduced goats has been reduced, but it originally caused ground instability and erosion which covers the entire island. The species is currently known from a recently-formed coastal plateau area below steep cliffs, where there is a threat of ground instability and land-slips. There is also a threat from predation by mice, which have not been eradicated yet. There is an increase in the frequency of droughts, which impacts both the species as well as adding to ground instability. The workstation of the Parque Natural da Madeira (the body that supervises the nature reserve) is at Fajã Grande.

Conservation Actions [top]

Conservation Actions: This species has long been considered Extinct by Waldén (1983) and Regnier et al (2008). There had been survey work in the period between 1970 and 2000 that had failed to locate populations, but in view of the nature of the terrain it was considered plausible that a small population may survey in region that were less accessible, hence was placed as Critically Endangered (Possibly Extinct) by Seddon (2008, 2011). Work on the rehabilitation of the vegetation following the removal of the goat populations started. Further work on rehabilitation of the plant communities on the islands are ongoing, and this may benefit the land-snail populations. There is survey work ongoing through a Life Project to monitor the status of this species and a species conservation action plan is planned for 2019.

The entire island of Deserte Grande is a candidate AZE for this and other species.

Citation: Teixeira, D., Cameron, R., Groh, K. & Seddon, M.B. 2018. Geomitra grabhami. The IUCN Red List of Threatened Species 2018: e.T156368A107734630. . Downloaded on 19 July 2018.
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