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Trechus terceiranus is a cave adapted endemic species from a single island, Terceira (Azores, Portugal). It has a relatively small extent of occurrence (EOO = 48 km²) and reduced area of occupancy (AOO = 44 km²). The species is known from ten isolated subpopulations, but also occurs in MSS. The area surrounding some of the caves is heavily impacted by human activities, and in the Algar do Carvão Show-Cave there is an ongoing impact of tourism visitation. A habitat management plan is needed and anticipated to be developed during the coming years. We suggest also as future measures of conservation the regular monitoring of the species (every ten years) and fencing the entrances of the caves where human intrusion and disturbance has been occurring. The species is assessed as Vulnerable (EN) due to the low habitat quality in many caves and the number of locations.
Trechus terceiranus is a widespread cave adapted endemic species from Terceira (Azores, Portugal) (Borges et al. 2010), known from several caves ((Algar do Carvão, Gruta da Achada, Gruta dos Balcões, Gruta do Caldeira, Gruta do Coelho, Gruta da Malha, Gruta do Natal, Gruta dos Principiantes, Gruta do Chocolate and Gruta de Santa Maria). The extent of occurrence (EOO) is 48 km² and the maximum estimated area of occupancy (AOO) is 44 km². The species was also found in the MSS (Milieu Souterrain Superficiel or Mesovoid Shallow Substratum) (Borges 1993) in the area of Pico Rachado, far from the location of know caves.
The species is particularly abundant in Terceira island. The area surrounding some of the caves is not protected and we assume some possible impacts for the isolated subpopulations.
This species occurs in several volcanic formations (lava tubes and volcanic pits) of Terceira island. This species is distributed by all hypogean environments of Terceira both in the cave and MSS- mesocavernous shallow stratum habitats (Borges 1993; Amorim 2005). It is a cavernicolous (i.e. a troglobitic species) predator and/or saprophagous species. Based on monthly data collected in Algar do Carvão show cave during ten years we can confirm that this species is active all the months but with high density between May and September.
The main current threat to this species is cave visitation by tourists and the impact of agriculture activities. However, there are several future potential threats: climatic changes (see Ferreira et al. 2016) that can change the conditions inside the caves; change in the road infraestructure around the caves; potential human recreational activities with radical cave visitation and geological events (volcanic activity and earthquakes).
The species is not protected by regional law. Part of its habitat is in a regionally protected area (Natural Park of Terceira). Degraded habitats should be restored and a strategy needs to be developed to address the future threat by climate change. Further research is needed into its ecology and life history in order to find extant specimens. It is necessary a monitoring plan for the invertebrate community in the habitat in order to contribute to the conservation of this species. A habitat management plan is needed and anticipated to be developed during the coming years.