MAIISG

Assessment Rationale:

TTarphius gabrielae is a single-island endemic species restricted to Pico island (Azores, Portugal) (Borges et al., 2017). It is a very rare species, with an restricted 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 only occurs in the soil and in dead trunks of endemic trees (mainly Euphorbia stygiana). 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; and (2) control of invasive species. The species is assessed as  Critically Endangered CR).

Geographic Range:

Tarphius gabrielae is a single-island endemic species restricted to Pico island (Azores, Portugal) (Borges et al., 2017), known from Natural Forest Reserve of Lagoa do Caiado. 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 native forest in Pico island (Borges et al. 2017). A continuing decline in the number of mature individuals is inferred from monitoring schemes and from the ongoing habitat degradation due to invasions of alien plants (Hedychium gardnerianum) (Borges et al. 2017), that are changing the structure of the forest and the cover of bryophytes and ferns in the soil decreasing the quality of the habitat with impacts on the species.

Habitat and Ecology

The species is very rare, and only occurs in a small patch of native forest in Pico island (Borges et al. 2017). It has an altitudinal range between 700 and 850 m. It is a nocturnal fungivorous species that lives in dead trunks of endemic trees and also in dead twigs of Euphorbia stygiana.

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 since this species is changing the habitat structure, namely decreasing the cover of bryophytes and ferns in the soil and promoting the spread of other plants. 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 in a regionally protected area (Natural Forest Reserve of Lagoa do Caiado in Pico island). Degraded habitats should be restored with the removal of invasive species. A strategy needs also to be developed to address the future threat by climate change. A habitat management plan is needed and anticipated to be developed during the coming years. 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 extant specimens in additional areas of native forest in Pico (e.g. Mistério da Prainha and Caveiro) 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. Monitoring every ten years using the BALA protocol will inform about habitat quality (see e.g. Gaspar et al. 2011).