Assessment Rationale:

Listed as Vulnerable because its extent of occurrence (EOO) is probably less than 20,000 km², its area of occupancy (AOO) is probably less than 2,000 km² and there is a continuing decline in the AOO and the habitat of the species due to strong anthropogenic pressure (agriculture, tourism), thus qualifying the species for Vulnerable.

Geographic Range:

Colletes dimidiatus is endemic to the Canary Islands where it is known from the islands of Gran Canaria, Tenerife, Gomera, El Hierro and La Palma (Hohmann et al. 1993, Kuhlmann et al. 2012). The extent of occurrence (EOO) in Europe and the EU 27 is 22,196 km² and the area of occupancy (AOO) is 124 km². However the EOO includes unsuitable habitat (e.g., ocean) so the EOO is smaller (less than 20,000 km²). The AOO is probably larger (though less than 2,000 km²), as the species has probably been under-recorded.

Population:

The populations of Colletes dimidiatus are likely to be small and seem to be isolated, presumably with no or little genetic exchange between them. This species is therefore considered severely fragmented given the extent of agricultural land transformation and touristic developments in lower parts of the Canary Islands; however, little information is currently available. A continuous decline in the habitat and also of the population size of the species can be assumed.

Habitat and Ecology

The habitats used by Colletes dimidiatus are unknown but likely are open vegetation types (e.g., Mediterranean shrub lands) that are declining on the Canary Islands. No information is available on flower visitation (Müller and Kuhlmann 2008).

Major Threat(s):

Likely threats are the anthropogenic loss (agriculture, touristic developments) of habitat (e.g., open vegetation types with bare soil), nesting sites and host plants, particularly on the dry southern parts of the Canary Islands that are prime tourist destinations.

Conservation Actions

This species is not listed in any National Red List or Red Data Book, and is not the subject of any targeted conservation action. It is recommended to conserve suitable habitats (e.g., open vegetation types with bare soil), nesting sites and the host plants of this species.

Further research is required to establish the current status of the species throughout its range and to identify the existing threats and trends.

It is not known if the species occurs in any protected area.