Assessment Rationale:

Trechus torretassoi is a single island endemic species restricted to São Miguel (Azores, Portugal). It has a very small extent of occurrence (EOO = 24 km²) and area of occupancy (AOO = 12 km²). The species occurs potentially only at two locations, but not found since 1985 despite some intensive search, and is potentially considered extinct. 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 major change in the habitat and the invasions of non-native plants in the two historical locations. Therefore, we suggest as future measures of conservation: (1) regular monitoring of the species; and (2) control of invasive species namely Hedychium gardnerianum. Therefore, it is assessed as Critically Endangered (Possibly Extinct). Further research is needed into its ecology and life history in order to find possible extant specimens.

Geographic Range:

Trechus torretassoi is a single island endemic species known from S. Miguel (Azores, Portugal) (Borges et al. 2010), and occurring historically only at Furnas and Sete Cidades volcanos. The extent of occurrence (EOO) is 24 km² and the maximum estimated area of occupancy (AOO) is 12 km². The species is considered possibly extinct (Terzopoulou et al.2015).

Population:

The species is particularly restricted and is very low in number of individuals. A continuing decline in the number of mature individuals is inferred from monitoring schemes, from massive land-use changes in the last 100 years and the ongoing habitat degradation due to invasions of alien plants. Despite intensive collecting efforts in the past 20 years, no specimens have been collected since 1985 and according to Terzopoulou et al. (2015) this species is possibly extinct. This species is assessed here as severely fragmented as at least 50% of its population can be found in subpopulations/in habitat patches 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 two sites that are isolated in a sea of pastures and Cryptomeria japonica plantations.

Habitat and Ecology

This species occurred originally in native forest in S. Miguel island (Azores), with an altitudinal range between 700 and 845 m. However, if still extant it should occur in exotic plantations of Cryptomeria japonica. It is a predator that lives in the soil associated with debris. In the last record in 1985 it was sampled associated with debris in a lake shore near a Cryptomeria japonica plantation (Gillerfors 1986).

Major Threat(s):

In the past, the species has probably strongly declined due to deforestation (Triantis et al.2010). The species is potentially considered extinct due to major historical land-use changes with clearing of original habitat (Terzopoulou et al. 2015). The most important ongoing threat to this species is Cryptomeria japonica wood & pulp plantations management and the spread of invasive plants (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. Based on Ferreira et al. (2016) the habitat will further decline as a consequence of climate change (increasing number of droughts and habitat shifting & alteration).

Conservation Actions

The species is not protected by regional law. 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 in Furnas and Sete Cidades. Therefore, degraded habitats in Furnas and Sete Cidades should be restored and a strategy needs to be developed to address the ongoing threat by invasive species and future threat by climate change.  Formal education and awareness is needed to allow future investments in restored habitats invaded by invasive plants. Further research is needed into its ecology and life history in order to find extant specimens in historical areas of Furnas and Sete Cidades.