Species

BackDiscula tetrica (R.T. Lowe, 1852)

Discula tetrica (R.T. Lowe, 1852)

  • Kingdom: Animalia
  • Phylum:
  • Class: Mollusca
  • Order: Gastropoda
  • Family: Hygromiidae
CR Critically Endangered
IUCN Red List Status:

Countries of Occurrence:
Portugal - Madeira

Archipelago(s):
Madeira

Assessor/s:
Seddon, M.B.

Reviewer/s:
Cameron, R., Groh, K., Cuttelod, A. & Neubert, E.

Contributor/s:

Facilitators / Compilers/s:


Assessment Rationale:

Fontaine et al. (2007)  listed this species as Extinct, however, there have been relatively few surveys in these islands over the last 50 years, as the islands remain in private ownership. The island has been subject to much change in vegetation since the introduction of goats, and the species was not recorded in surveys by Cameron and Cook (1999). It is likely that the species is extinct, given the size of the shell, however, given the conservation actions in recent years and the planned programme to restore vegetation, as well as the high cliffs that are inaccessible, it is considered more prudent to list the species as Critically Endangered, Possibly Extinct.

Geographic Range:

This species is endemic to Desertas (Madeiran islands); Wollaston (1878) reported that it was scarce on Bugio in the 1860s. Cameron and Cook (1999) did not record this species in their survey work and hence the species may be extinct or extremely rare now on the island.

Regions:
Portugal - Madeira
Extent of Occurrence (EOO):
(km2)
Area of Occupancy (AOO):
(km2)
Elevation Lower Limit:
(m)
Elevation Upper Limit:
(m)
Biogeographic Realms:
Palearctic
Presence:
Extant
Origin:
Endemic Madeira
Seasonality:
Resident

Population:

This species has not been recorded for over 50 years and was reported to be rare over 140 years ago (Wollaston 1878). Wollaston (1878) described the species as living amongst lichens on the sea-cliffs, however these  cliffs are quite inaccessible, and hence difficult to sample, although the species has a large, conspicuous discoid shell.

Habitat and Ecology

Wollaston (1878) described the species as living amongst lichens on the sea-cliffs. These  cliffs are quite inaccessible, and hence difficult to sample, although the species has a large, conspicuous discoid shell.

Major Threat(s):

The island has been subject to much change in vegetation since the introduction of goats, which lead to soil erosion and changing vegetation.

Conservation Actions

It is likely that the species is extinct, given the size of the shell, however, given the conservation actions removing the goats in recent years and the planned programme to restore vegetation, so further surveys are recommended at regular intervals for this species.