MAIISG

Assessment Rationale:

Rugathodes acoreensis is an endemic comb-footed spider species occurring on eight islands of the Azorean archipelago (Azores, Portugal) (only absent in Corvo) (Borges et al. 2010). It has a relatively large Extent of Occurrence (EOO = 42,873 km²) and a small Area of Occupancy (AOO = 320-372 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 mosses and ferns. Ongoing threats, such as from invasive plant species, are thought to be leading to continuing declines, and with there being >10 locations the species is assessed as Near Threatened (NT).

Geographic Range:

Rugathodes acoreensis is a comb-footed spider species that only occurs on eight islands of the Azorean archipelago (Azores, Portugal) (absent in Corvo) (Borges et al. 2010). Within these eight 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 S. Maria). The Extent of Occurrence (EOO) is estimated to be 42,873 km2 and the Area of Occupancy (AOO) is estimated to be 320-372 km2 . 

Population:

This can be considered one of the most abundant endemic Azorean spider species, but it is most abundant in native forest. In at least eight locations the subpopulations are threatened due to the ongoing spread of invasive plants, which are changing the structure of the habitat. 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, but also occurs in some herbaceous vegetation. 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 high elevation sites with pristine forests dominated by Juniperus brevifolia, Laurus azorica and Ilex perado subsp. azorica, and 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 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 in 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 on 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 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. 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).