Assessment Rationale:

Tarphius pomboi is a single-island endemic species restricted to S. Maria island (Azores, Portugal) (Borges et al.2010, 2017). It is a rare species, with a restricted extent of occurrence (20 km²) and area of occupancy (20 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 occurs in four patches of native and exotic vegetation. In the past, the species has probably strongly declined due to changes in habitat size. The only patch of native vegetation where it occurs is under severe threat due to invasive plants. 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 therefore assessed as Critically Endangered (CR).

Geographic Range:

Tarphius pomboi is a single-island endemic species restricted to S. Maria island (Azores, Portugal) (Borges et al. 2010, 2017), known from Natural Forest Reserve of Pico Alto (S. Maria). The extent of occurrence (EOO) is 20 km² and the maximum estimated area of occupancy (AOO) is 20 km².

Population:

It is a rare species that occurs in native forests in Sta. Maria 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 (namely Pittosporum undulatum and Hedychium gardnerianum) and the Cryptomeria japonicamanagement (Borges et al. 2017).  Some of the exotic patches may disappear in near future for the implementation of pastures with further impacts on the population abundance. This species is assessed here as severely fragmented as at least 50% of its population can be found in subpopulations that are 1) smaller than would be required to support a viable population, and 2) separated from other habitat patches by a large distance. In fact, the species occurs in fragments that are isolated in a matrix of pastures.

Habitat and Ecology

This is a rare species that occurs in the native forests of Santa Maria island dominated by the endemic plants Morella faya, Picconia azorica and Erica azorica  but also the invasive Pittosporum undulatum (Borges et al. 2017). It has an altitudinal range between 200 and 500 m. This is a nocturnal fungivorous species that lives in the soil. This is an univoltine species.

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. 2010), 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. Cryptomeria japonica wood & pulp plantations management can also be a problem. 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). An additional future threat will be the transformation of some of the exotic patches in pastures with further impacts on the population abundance.

Conservation Actions

The species is protected by regional law (RAA 2012). Its habitat is in a regionally protected area (Natural Forest Reserve of Pico Alto in Sta Maria 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 and creation of pastureland. 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 additional extant specimens in the Pico Alto surrounded areas of exotic forest 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).