Assessment Rationale:

Tarphius rufonodulosus is a single-island endemic species restricted to S. Maria island (Azores, Portugal) (Borges et al. 2010, 2017). It has an extent of occurrence of 28 km² and an area of occupancy of 28 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 particularly abundant in the canopies of native trees (e.g. Picconia azorica) and under-bark of dead trees both in native and exotic forests (dominated by Acacia sp. and Cryptomeria japonica) (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; and (2) control of invasive species, namely Pittosporum undulatum. The species is assessed as Critically Endangered (CR).

Geographic Range:

Tarphius rufonodulosus 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 28 km² and the maximum estimated area of occupancy (AOO) is 28 km².

Population:

The species is abundant, particularly in the canopy of several endemic trees in a patch of native forest of Santa Maria Island. 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 the Cryptomeria japonica pulp plantations management (Borges et al. 2017). Some of the patches with exotic plants 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

The species is particularly abundant in the canopies of native trees (e.g. Picconia azorica) and under-bark of dead trees both in native and exotic forests (dominated by Acacia sp. and Cryptomeria japonica). 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 Pittosporum undulatum  and Hedychium gardnerianum that 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 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). 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 not protected by regional law. 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. A habitat management plan is needed and anticipated to be developed during the coming years. Since this species is an icon of the 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 more forest areas in S. Maria and obtain information on population size, distribution and trends. It is also necessary 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).