IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group

Species

BackBoettgeria crispa (Lowe, 1831)

Boettgeria crispa (Lowe, 1831)

  • Kingdom: Animalia
  • Phylum: Mollusca
  • Class: Gastropoda
  • Order: Pulmonata
  • Family: Clausiliidae
NT Near Treatened
IUCN Red List Status:

Countries of Occurrence:
Portugal - Madeira

Archipelago(s):
Madeira

Reviewer/s:

Contributor/s:

Facilitators / Compilers/s:


Assessment Rationale:

This species is endemic to the Madeiran Islands, where it is found between 300 to 1,000 m elevation. It is more frequently found in the northern areas on the laurisilva zone. It is present in the intermediate zone with the mature trees and cliffs, and is not found higher on the ridges. The extent of occurrence (EOO) is estimated at 212 km2 and the area of occupancy (AOO) at 124 km2 . Surveys for this species have reported a general decline since 2006. Surveys between 2006 and 2014 were carried out in numerous sites originally visited in the 1980s to 1999. In comparison, the number of populated sites has declined by at least 30% and the abundance of individuals at sites has declined significantly more (60 to 80%). The main threats that may explain these decline are the loss of large trees due to storm damages or fires, microclimate changes towards more windy, less rainy conditions; and wildfires. Since the decline over the last ten years is of at least 30% in the area of occupancy (AOO) and 60% in the numbers of mature individuals, the species is assessed as Endangered (EN B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v)). A monitoring programme for this species is going to be carried out in the next few years, and conservation actions such as habitat management are strongly suggested.

Geographic Range:

This species is endemic to Madeira Island, where it is found from 300 to 1,000 m elevation. It is more frequently found in the northern areas on the laurisilva zone. It is present in the intermediate zone with mature trees and cliffs, and is not found higher on the ridges. Surveys for this species have reported a general decline since 2006. Surveys between 2006 and 2014 were carried out in numerous sites originally visited in the 1980s to 1999. In comparison, the number of populated sites has declined by at least 30% and the abundance of individuals at sites has declined significantly more (60 to 80%) (K. Groh et al. pers. comm. 2016). In general, it can reliably be found in only four sites during visits (D. Teixeira pers. comm. 2016). The surveys have been conducted under suitable conditions and hence this decline is not considered to be a sampling artifact.

Regions:
Portugal - Madeira
Extent of Occurrence (EOO):
212 (km2)
Area of Occupancy (AOO):
124 (km2)
Elevation Lower Limit:
300 (m)
Elevation Upper Limit:
1000 (m)
Biogeographic Realms:
Palearctic
Presence:
Extant
Origin:
Endemic Madeira
Seasonality:
Resident

Population:

The population is believed to be declining, but it requires skilled surveyors rather than general surveyors to locate the species. Declines for the populations of this species have been observed in the last ten years. Surveys between 2006 and 2014 have been carried out in areas originally visited in the 1980s to 1999. In comparison, the number of populated sites has declined by at least 30% and the abundance of individuals at sites has declined significantly more (60 to 80%) (K. Groh et al. pers. comm. 2016). In general, it can reliably be found in only four sites during visits (D. Teixeira pers. comm. 2016). The surveys have been conducted under suitable conditions and hence this decline is not considered to be a sampling artifact.

Habitat and Ecology

The species is usually found on trunks of large trees within Laurisilva forest, where it is found in crevices of the bark, or on leaf-litter at base of trunks. It is sometimes found on the rock-crags, where it lives amongst leaf litter on ledges. Declines in population abundance have been observed, and there has been a decline in the quality of the habitat as a result of forest fires. There has also been an increase in the frequency of windy days, and a decrease in the number of rainy days.

Major Threat(s):

There are several major threats. The loss of large trees due to storm damage or fire remain as ongoing threats. Additional threats are the increased frequency of windy days and a decrease in the number of rainy days, which can change the microclimate and macrohabitat of the area. These climate changes are particularly affecting the north of the island, which is the area where the species has been historically more abundant. Forest fires have impacted 30% of the occupied habitats in the last ten years (D. Teixeira pers. comm. 2016) and remain as a constant threat to the population, especially on the south side of the island. The four sites where the least impact has been seen are in the upper parts of the Laurisilva or sites that are more sheltered. The more impacted sites are those at intermediate elevations.

Conservation Actions

Habitat management in the Laurisilva zone is required to ensure the regeneration of large trees, as well as management of the woodland to retain large trees and other shaded rocky habitats that could be suitable for the species. Nearly 80% of the sites lie in a protected area (either Natura 2000 or Madeira Nature Park). There will be a monitoring programme for this species as part of the Natura 2000 designation.