MAIISG

Assessment Rationale:

Tarphius depressus is a single-island endemic species restricted to Sta. Maria island (Azores, Portugal) (Borgeset al. 2010, 2017). It has an extent of occurrence of 24 km² and an area of occupancy of 24 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 mainly under bark of several trees (subcortical), both endemic and exotic. In the past, the species has probably strongly declined due to changes in habitat size. The management of Cryptomeria plantations could be also a problem for the subpopulations living in this habitat. Therefore, we suggest as future measures of conservation: (1) a long-term monitoring plan of the species; and (2) control of invasive species, namely Hedychium gardnerianum. The species is assessed as Critically Endangered (CR).

Geographic Range:

Tarphius depressus is a single-island endemic species restricted to Sta. 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 24 km² and the maximum estimated area of occupancy (AOO) is 24 km².

Population:

The species is abundant in native and exotic forests of 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 japonica management (Borges et al. 2017). 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

The species is particularly abundant. It occurs under bark of several trees (subcortical), both endemic and exotic. It also occurs in exotic forests dominated by Cryptomeria japonica (Borges et al. 2017). This species has an altitudinal range between 200 and 500 m. It is a nocturnal fungivorous 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. 2017), particularly Hedychium gardnerianum. The management of Cryptomeria japonica plantations could be also a problem for the subpopulations living in this habitat. 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 Pico Alto in Santa 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.  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 more patches of exotic vegetation around Pico Alto 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).