MAIISG

Assessment Rationale:

Olisthopus inclavatus is endemic to Azores, occurring in only one islands (S. Maria). It has a very small extent of occurrence (EOO = 35 km²) and reduced area of occupancy (AOO = 32 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 and human activities (forestry and agriculture). The species is particularly restricted to very small fragmented patches of exotic forest with a marginal occurrence in semi-natural pastures. In the past, the species has probably strongly declined due to changes in habitat size and quality. Based upon the small geographic range of the species and continuing decline of its habitat area and quality, it is assessed as Critically Endangered.

Geographic Range:

Olisthopus inclavatus is a single island endemic species from Santa Maria (Azores, Portugal) (Borges et al. 2010), known from few patches of highly modified lowland forests. The extent of occurrence (EOO) is 35 km² and the maximum estimated area of occupancy (AOO) is 32 km².

Population:

The species is particularly restricted but the abundance is relatively high in the known localities. A continuing decline in the number of mature individuals is inferred from the ongoing habitat degradation due to invasions of alien plants and the destruction of exotic plantations for the implementation of pastures. This species is assessed here 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.

Habitat and Ecology

The species occurs in exotic forests (dominated by Cryptomeria japonica, Acacia spp.), semi-natural forests and in semi-natural pastures in Santa Maria island, with an altitudinal range between 150 and 300 m, being relatively widespread (Meijer et al. 2011). It is a nocturnal predator that lives in native trees and in the soil.

Major Threat(s):

In the past, the species has probably strongly declined due to changes in habitat size and quality. Currently the modified habitats where it occurs are being highly modified and disturbed, namely pactches of  Cryptomeria japonica and Acacia sp.. Agriculture and wood & pulp productions are also a major threat. 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. Degraded habitats should be restored and a strategy needs to be developed to address the ongoing impact of invasive plants and future threat by climate change. A habitat management plan is needed and anticipated to be developed during the coming years. Formal education and awareness is needed to allow future investments in restored habitats invaded by alien plants. Further research is needed into its ecology and life history in order to find extant specimens 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 in some of the isolated exotic Acacia spp. patches.