Assessment Rationale:

Sancus acoreensis is an endemic long-jawed orb weaver spider species occurring in seven islands of the Azorean archipelago (Azores, Portugal) (only absent in Graciosa and Corvo) (Borges et al. 2010). It has a relatively large Extent of Occurrence (EOO = 38,863 km²) and a small Area of Occupancy (AOO = 216-752 km²). This species occurs mainly in Azorean pristine native forest at mid and high elevation sites with forests dominated by Juniperus brevifolia, Laurus azorica and Ilex perado subsp. azorica and densely covered by shrubs of Vaccinium cylindraceum and Myrsine spp. Ongoing threats, such as from invasive plant species, are thought to be causinf continuing declines, and so the species is assessed as Vulnerable (VU).

Geographic Range:

Sancus acoreensis is an endemic long-jawed orb weaver spider species occurring on seven islands of the Azorean archipelago (Azores, Portugal) (only absent in Graciosa and Corvo) (Borges et al. 2010). Within these seven islands it is known from eighteen Natural Forest Reserves: Caldeiras Funda e Rasa and Morro Alto e Pico da Sé (Natural Park of Flores); Caldeira do Faial and Cabeço do Fogo (Natural Park of Faial); Mistério da Prainha, Caveiro and Caiado (Natural Park of Pico); Pico Pinheiro and Topo (Natural Park of S. Jorge); Biscoito da Ferraria, Pico Galhardo, Caldeira Guilherme Moniz, Caldeira Sta. Bárbara e Mistérios Negros and Terra Brava (Natural Park of Terceira); Atalhada, Graminhais and Pico da Vara (Natural Park of S. Miguel) and Pico Alto (Natural Park of Sta. Maria). The estimated Extent of Occurrence (EOO) is 38,863 km2 and the estimated Area of Occupancy (AOO) is 216-752 km2 .

Population:

This can be considered one of the most abundant endemic Azorean spider species, but it is most abundant in native forest. Current Population Trend: Decreasing.

Habitat and Ecology

The species occurs mainly in native forests and builds its web in the canopies of endemic trees and shrubs, although also associated with herbaceous vegetation, such as small individuals of Vaccinium cylindraceum and Myrsine spp. This generalist predator is active during the night and, based on long-term data with SLAM traps (Borges et al. 2017), it occurs in all seasons, but with adults being dominant in late spring and summer. The species tends to be more abundant at sites with pristine forests dominated by Juniperus brevifolia, Laurus azorica and Ilex perado subsp. azorica and densely covered by shrubs of Vaccinium cylindraceum and Myrsine spp. Systems: Terrestrial.

Major Threat(s):

In the past, the species has probably strongly declined due to changes in habitat size and quality (Triantis et al. 2010). However, the species seems to have survived in the remaining native forests of the Azores, mostly at mid and high elevation pristine forests. The main current threat is the spread of invasive plant species namely Hedychium gardnerianum and Pittosporum undulatum on most islands, and Clethra arborea on S. Miguel, which are changing the structure of the forest and the cover of endemic trees and shrubs. 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, but its habitat is in regionally protected areas (Natural Parks of Faial, Flores, Pico, S. Jorge, Terceira, S. Miguel and S. Maria). Degraded habitats in some islands, degraded due to invasive plant species, should be restored (e.g. S. Maria) and a strategy needs to be developed to address the current threat posed by invasive species on all islands, as well as the future threat posed by climate change. A habitat management plan is needed and is anticipated to be developed during the coming years. Formal education and awareness is needed to allow future investments in restored habitats invaded by invasive plants; while further research is needed into its ecology and life history in order to obtain adequate information on population size, distribution and trends. An area-based management plan is also necessary for the most disturbed sites, including invertebrate monitoring to contribute to a potential species recovery plan. Monitoring every ten years using the BALA protocol will inform about habitat quality (see e.g. Gaspar et al. 2011).