Geomitra grabhami

[Melanie]

Scientific Name: Geomitra grabhami
Species Authority: (Wollaston, 1878)
Assessment Information [top]
Red List Category & Criteria: Critically Endangered B1ab(iii) ver 3.1
Year Published: 2013
Date Assessed: 2010-08-31
Assessor(s): Seddon, M.B.
Reviewer(s): Cameron, R., Groh, K., Cuttelod, A. & Neubert, E.
Justification:
Geomitra grabhami has not been recorded since the 1980s and its status is uncertain. At the time of description, the species was common on the north end of Deserta Grande according to Wollaston (1878). It is possible that the impact of grazing has modified the habitats in this area. Cameron and Cook (1999) surveyed ten sites on Deserta Grande, as well as making earlier collections in 1970 and 1981 and failed to find the species. Regnier et al. (2009) listed this species as Extinct, however, although there have been recent surveys that failed to find the species, given the amount of inaccessible slopes and the fact that the goats have been removed from Deserta Grande, which will allow the stabilisation of the vegetation and gradual return to past vegetation on the slopes, the species is still considered as Critically Endangered, Possibly Extinct, until further data shows the recovery of the vegetation has not lead to recovery of the species. Further work on rehabilitation of the plant communities on the islands are ongoing, and this may benefit the land-snail populations (D. Teixeira pers. comm. 2010).
Geographic Range [top]
Range Description: This species is endemic to the Madeiran islands. It is known from the northern end of Deserta Grande, where it was recorded by Groh and Hemmen (1986), but not refound by Cameron and Cook (1999). The species has had a similar distribution for over 100 years (Wollaston 1878).
Countries:
Possibly extinct:
Portugal (Madeira)
Range Map: Click here to open the map viewer and explore range.
Population [top]
Population: There are no records for over 40 years.
Population Trend: Unknown
Habitat and Ecology [top]
Habitat and Ecology: This species was originally described as living amongst lichen growing on rocks (Seddon 2008).
Systems: Terrestrial
Use and Trade [top]
Use and Trade: The species is not known to be utilised, although 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 vegetation is gradually recovering.
Conservation Actions [top]
Conservation Actions: The goats have been removed from Deserta Grande, which will allow the stabilisation of the vegetation and gradual return to past vegetation on the slopes. Hence the species is still considered as possibly extinct, until further data shows the recovery of the vegetation has not lead to recovery of the species. Further work on rehabilitation of the plant communities on the islands are ongoing, and this may benefit the land-snail populations.

www.iucnredlist.org/details/156368/0

[Melanie]

Rediscovered in 2013.

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:

2011 – Critically Endangered (CR)

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: 4 ♦ Continuing 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: 400-500 ♦ Continuing decline of mature individuals: Unknown
♦ Extreme fluctuations: Unknown ♦ Population 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.

www.iucnredlist.org/details/156368/0