MAIISG

Assessment Rationale:

Tarphius relictus  is a single-island endemic species restricted to Terceira island (Azores, Portugal) (Borges et al. 2017). It has an reduced extent of occurrence (8 km²)  and area of occupancy  (8 km²). There is a continuing decline in the EOO, AOO, extent and quality of habitat as well as the number of mature individuals as a result of the invasions of non-native plants. The species is very rare, and only occurs in a small, disturbed site covered by exotic trees at low altitude, in Terceira island. Due to very restricted distribution, this species is the most endangered Tarphius species in the Azores (Borges et al. 2017). In the past, the species has probably strongly declined due to changes in habitat size. Therefore, we suggest as future measures of conservation: (1) a long-term monitoring plan of the species; (2) control of invasive species, and (3) translocation of individuals for the pristine patches of forest in the high altitude sites of Terceira Island (i.e. ex.situ conservation). The species is therefore assessed as Critically Endangered (CR).

Geographic Range:

Tarphius relictus is a single-island endemic species restricted to Terceira island (Azores, Portugal) (Borges et al. 2017), known in only one location (Biscito das Fontinhas), being a very rare species. The extent of occurrence (EOO) is 8 km² and the maximum estimated area of occupancy (AOO) is 8 km².

Population:

The species is very rare and only occurs in a small patch of exotic forest (Acacia spp.) in Terceira island (Borges et al. 2017). This is the most endangered Tarphius species in the Azores, due to restricted area of distribution and the existence of invasive plant species (Borges et al. 2017).

Habitat and Ecology

The species is very rare, and only occurs in a small, disturbed site covered by exotic trees at low altitude, in Terceira island (Borges et al. 2017). It has an altitudinal range between 200 and 300 m. It is a nocturnal fungivorous species that lives in the soil and in dead wood.

Major Threat(s):

In the past, the species has probably strongly declined due to changes in habitat size and quality (Triantis et al. 2010). Currently, the rapid advance and expansion of invasive plants species is the major threat (Borges et al. 2017), particularly Hedychium gardnerianum and Pittosporum undulatum since are changing the habitat structure, namely decreasing the cover of bryophytes and ferns in the soil and promoting the spread of other plants. The management of the Acacia spp. patches could be also a problem for the unique surviving subpopulation. Based on Ferreira et al. 2016 the habitat will further decline as a consequence of climate change (increasing number of droughts and habitat shifting and alteration).

Conservation Actions

The species is not protected by regional law. Its habitat is now included in the Natural Park of Terceira (IUCN Type V level of protection). Degraded habitats should be restored and a strategy needs to be developed to address the future threat by climate change.  We suggest as a possible additional measure of conservation the translocation of individuals for the pristine patches of forest in the high altitude sites of Terceira Island (i.e. ex.situ conservation). Since this species is an icone of the relict native Azorean forests, it is suggested that some awareness measures should be put in practice. Further research is needed into its ecology and life history in order to find additional extant specimens in some meddle elevation forest patches in Terceira island and obtain information on population size, distribution and trends. It is also necessary an area-based management plan and a monitoring plan for the invertebrate community in the habitat in order to contribute to perform a species potential recovery plan.