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Xerocrassa ebusitana 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Gastropoda Stylommatophora Hygromiidae

Scientific Name: Xerocrassa ebusitana
Species Authority: (Hidalgo, 1869)
Taxonomic Notes: The taxonomical status of this species requires clarification. The specific placement of this polytypical species has suffered diverse modifications following the works of Schröder (1978), Puente (1994) and Pons and Palmer (1996).

Puente (1994) considers the following subspecies of X. ebusitana (15):

  • X. e. ebusitana is the form most widely distributed, occupying the southern half of Ibiza, and Conillera, Formentera, Espardell and Espalmador.
  • X. e. ortizi ia found in the northern part of Ibiza as well as in the islet Tagomago
  • X. e. hortae only live in the approximately 200 m2 del Illot de S’Hort
  • X. e. canae live in the Illa d’es Canar
  • X. e. cisternasi in Illa Grossa de Sta. Eulària
  • X. e. redonae in the Illa Redona de Sta. Eulària
  • In the southern islands of Ibiza live X. e. vedrae (Vedrá) and X. e. vedranellensis (Vedranell)
  • In the west of Ibiza, in the islands of Ses Bledes live X. e. scopulicola (Na Gorra, Bleda Na Bosc y Bleda Plana), X. e. conjugens (Escull Vermell), X. e. calasaladae en S’Illeta, in front of Cala Saladaand X. e. margaritae in Ses Margalides, island in front of Santa Agnès
  • The northern islands of Ibiza are home to X. e. muradae (Illa Murada), X. e. calderensis (Illa d’en Calders)and X. e. mesquidae (Illot de Sa Mesquida).

Recently Beckmann (2007) has segregated X. cisternasi from X. ebusitana of Ibiza, assigning to the first the current subspecies (14) and the four fossil subspecies (Sacchi 1954, Paul 1984) to the second.




Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2011
Date Assessed: 2010-10-01
Assessor(s): Martínez-Ortí, A.
Reviewer(s): Arrébola, J., Lutz, M.L., Nichols, C. & Neubert, E.
Justification:
This species is endemic to the Balearic islands (Spain), where it is found on the Ibiza and Formentera and their surrounding islands and islets. This species has given rise to several subspecies, and taxonomic research is needed to establish if the subspecies are separate valid species. This species has an extent of occurrence of 1,800 km2, an area of occupancy of 288 km2 and 14 locations. The main threats to this species come from fires and tourism, which are causing a decline in the quality and extent of its habitat, therefore it is assessed as Near Threatened (NT B1b(iii) + B2b(iii).

Geographic Range [top]

Range Description:Xerocrassa ebusitana is endemic to the Balearic islands (Spain), where it is found on Ibiza and Formentera and their surrounding islands and islets, where it has formed several subspecies.

X. e. ebusitana is the form most widely distributed, occupying the southern half of Ibiza, and Conillera, Formentera, Espardell and Espalmador.
X. e. ortizi ia found in the northern part of Ibiza as well as in the islet Tagomago.

The remaining subspecies have extremely limited distributions, restricted to the surrounding islands of Ibiza:
  • X. e. hortae only live in the approximately 200 m2 del Illot de S’Hort
  • X. e. canae live in the Illa d’es Canar
  • X. e. cisternasi in Illa Grossa de Sta. Eulària
  • X. e. redonae in the Illa Redona de Sta. Eulària
  • In the southern islands of Ibiza live X. e. vedrae (Vedrá) and X. e. vedranellensis (Vedranell)
  • In the west of Ibiza, in the islands of Ses Bledes live X. e. scopulicola (Na Gorra, Bleda Na Bosc y Bleda Plana), X. e. conjugens (Escull Vermell), X. e. calasaladae en S’Illeta, in front of Cala Saladaand X. e. margaritae in Ses Margalides, island in front of Santa Agnès
  • The northern islands of Ibiza are home to X. e. muradae (Illa Murada), X. e. calderensis (Illa d’en Calders)and X. e. mesquidae (Illot de Sa Mesquida).
Countries occurrence:
Native:
Spain (Baleares)
Additional data:
Estimated area of occupancy (AOO) - km2:288
Number of Locations:14
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:There are no demographic studies of this species. Gasull (1964), referring to the genus Xerocrassa  (found in the Balearic islands in general), noted that their population density was usually very high. Research is necessary to determine the population status of this species. Recent visits (Martínez-Ortí, pers. comm., 2011) to various locations on Formentera found two extant populations; on Ibiza only shells were discovered. Schröder (1978) said regarding X. e. hortae, that there is a danger of extinction in the coming years, with only few specimens observed alive. This could also be the case on other islands and subspecies.
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:

This species lives in ruderal places (edges of roads and paths), rocky coasts and rocky areas with small amounts of vegetation, where it is found in crevices. It is also found in shrub habitats.

This species is an intermediate host of the juveniles of the digenean trematode Dollfusinus frontalis. The adults of D. frontalis are found in the Algerian hedgehog (Atelerix algirus) and the nasal passages of rodents such as the dormouse (Eliomys quercinus ophiusae) and the invasive black rat (Rattus rattus).

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: This species is collected for shell specimens.

Threats [top]

Major Threat(s): The main threats to this species are from fires and anthropogenic pressure (mainly tourism, specimen collecting, urban expansion, recreational activities and road extension). This species is also an intermediate host of the juveniles of the digenean trematode Dollfusinus frontalis, which is spread by the invasive black rat.

Conservation Actions [top]

Conservation Actions: This species is included in the Balearic Catalogue of Threatened Species (BOIB, no. 66, 15/05//2008) under the category of species of 'special interest'. This category provides the species with a management plan. The presence and population size of the invasive black rat on each of the islands needs to be determined, as it spreads the digenean trematode Dollfusinus frontalis, with the eventual aim of eradication from the islands. Controls need to be put in place to prevent the indiscriminate collection of specimens by collectors.

Citation: Martínez-Ortí, A. 2011. Xerocrassa ebusitana. The IUCN Red List of Threatened Species 2011: e.T156741A4990601. . Downloaded on 29 March 2017.
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