MAIISG

Assessment Rationale:

Acorigone acoreensis is a money spider occurring on seven islands of the Azorean archipelago (Azores, Portugal) (only absent in Corvo and Graciosa) (Borges et al. 2010). It has a relatively large Extent of Occurrence (EOO = 37,399 km²) and a small Area of Occupancy (AOO = 140-256 km²). This species occurs mainly in Azorean pristine native forest at high elevation sites with forests densely covered by mosses and ferns. Ongoing threats, such as from invasive plant species, are considered to be causing ongoing declines, and so the species is assessed as Vulnerable (VU). 

Geographic Range:

Acorigone acoreensis is a money spider species occurring on seven islands of the Azorean archipelago (Azores, Portugal) (only absent in Corvo and Graciosa) (Borges et al. 2010). Within these seven islands it is known from sixteen Natural Forest Reserves: Caldeiras Funda e Rasa and Morro Alto e Pico da Sé (Natural Park of Flores); Caldeira do Faial (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); Graminhais and Pico da Vara (Natural Park of S. Miguel) and Pico Alto (Natural Park of S. Maria). The Extent of Occurrence (EOO) is 37,399 km2 and the estimated Area of Occupancy (AOO) is 140-256 km2 .

Population:

This can be considered one of the most abundant endemic Azorean spider species, but it is most abundant in native forest. Due to the ongoing spread of invasive plants, which are changing the structure of the habitat to be unsuitable for this species, there is an inferred decline in mature individuals. Current Population Trend: Decreasing.

Habitat and Ecology

The species occurs mainly in native forests, building their sheet weaver webs in the canopies of endemic trees. This is a generalist predator that is also frequently found on the trunks of trees associated with mosses and lichens, together with another small generalist beetle predator, the endemic rove beetle, Atheta dryochares (Coleoptera, Staphylinidae). It 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 summer and early autumn. The species tends to be more abundant at high elevation sites with pristine forests densely covered by mosses and ferns. 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 in high elevation pristine forests. The current main threats are from Cryptomeria japonica wood and pulp plantations (mostly in S. Maria island), and the spread of invasive plant species, namely Hedychium gardnerianum and Pittosporum undulatum, on most islands, and Clethra arboreal in S. Miguel, which are changing the structure of the forest and the cover of bryophytes and ferns, with impacts on web construction. 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, and the future threat from climate change. A habitat management plan is needed and one is anticipated to be developed during the coming years. Formal education and awareness are 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. It is also necessary an area-based management plan for some disturbed sites and a monitoring plan for the wider invertebrate community in its habitat in order to contribute to a potential future species recovery plan. Monitoring every ten years using the BALA protocol will inform about habitat quality (see e.g. Gaspar et al. 2011).