IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group

Species

BackAtlantica calathoides (Lowe, 1863)

Atlantica calathoides (Lowe, 1863)

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

Countries of Occurrence:
Portugal - Madeira

Archipelago(s):
Madeira

Assessor/s:
Dinarte Teixeira

Reviewer/s:
Cameron, RAD, Groh, K. & Seddon, M.B.

Contributor/s:

Facilitators / Compilers/s:


Assessment Rationale:

This species is endemic to the Madeira Archipelago (Portugal), where it is known from Deserta Grande Island (Cameron and Teixeira 2013). The major threat is predation by mice (Mus musculus) and native carabids (Scarites abbreviatus desertarum). The habitat cover is also susceptible to changes due to droughts, landslides and goat grazing (D. Teixeira pers comm. 2016). The species is assessed as Critically Endangered under criteria B2ab(iii,v), based on its occurrence in a single location, the reported fluctuations in the population in the last ten years, the observed declines due to predation and the habitat degradation.

Geographic Range:

This species is endemic to the Madeiran Archipelago (Portugal), where it is known from Deserta Grande Island. It was rediscovered in 2008 by Silva and Teixeira (Cameron and Teixeira 2013, D. Teixeira pers. comm 2016). It is also present as a Quaternary fossil on Bugio (R. Cameron pers. comm. 2016). There are recent records of living specimens of this species from two sites on Deserta Grande (D. Teixeira pers. comm. 2016), one of them found on the northwestern end and the second one on the southwestern end.

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

Population:

The population is decreasing. The species was rediscovered in 2008, on both known subpopulations (D. Teixeira pers. comm. 2016). There have been also large fluctuations in monitored subpopulations over the last ten years

Habitat and Ecology

This species occurs in very deep ravines, at intermediate altitudes, on habitats dominated by common bracken (Pteridium aquilinum). It is found generally near the base of the plants, in the leaf litter or beneath rocks (D. Teixeira pers. comm. 2016). Paiva (1867) found it originally associated with lichens, although Wollaston (1878) doubted that Paiva's record was of recent material (R. Cameron pers. comm. 2016).

Major Threat(s):

The main threats are predation by mice (Mus musculus) and native carabids (Scarites abbreviatus desertarum), and also habitat shifting or alteration and fragmentation due to severe droughts, goat grazing and landslides. 

Conservation Actions

A population study and a monitoring scheme are ongoing under the LIFE Recover Natura Project (2013- 2017), along with a species ecology study. A species conservation plan will be produced in 2017 and implemented through the post-LIFE project (2018-2022). As an indirect measure, a continued control programme for goat populations has been carried out for the last 20 years, which should be enhancing the species habitat restoration.