IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group


BackTyphochrestus acoreensis Wunderlich, 1992

Typhochrestus acoreensis Wunderlich, 1992

Sheetweb and dwarf weavers, Sheetweb spider, Dwarf spider

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Arachnida
  • Order: Araneae
  • Family: Linyphiidae
CR Critically Endangered
IUCN Red List Status:

Countries of Occurrence:
Portugal - Azores


Russell, N.

Lamelas-López, L. & Mendonca, E.

Facilitators / Compilers/s:

Assessment Rationale:

Typhochrestus acoreensis is a single-island endemic species, restricted to Terceira Island (Azores, Portugal) (Borges et al. 2010). It is a rare species, with a restricted Extent of Occurrence (EOO) (4-24 km 2) and Area of Occupancy (AOO) (4-24 km²), but it is likely to be at the upper end of this estimate. The species occurs in a single patch of native forest (at Biscoito da Ferraria Reserve). 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 the impact of Cryptomeria japonica plantations, with the destruction of the main original site. Therefore, we suggest as future measures of conservation: (1) a long-term monitoring plan of the species; (2) control of invasive species, and (3) avoid the expansion of Cryptomeria japonica plantations in the Pico Alto area. The species is assessed as Critically Endangered (CR).

Geographic Range:

Typhochrestus acoreensis is a single-island endemic species restricted to Terceira island (Azores, Portugal) (Borges et al. 2010), known from Natural Forest Reserve of Biscoito da Ferraria (Natural Park of Terceira). The Extent of Occurrence (EOO) is 4-24 km2 and the maximum estimated Area of Occupancy (AOO) is 4-24 km2.

Portugal - Azores
Extent of Occurrence (EOO):
4-24 (km2)
Area of Occupancy (AOO):
4-24 (km2)
Elevation Lower Limit:
352 (m)
Elevation Upper Limit:
793 (m)
Biogeographic Realms:
Endemic Azores


This is a very rare species and only known from a single sustainable subpopulation. After its scientific description, no individuals were found during BALA project intensive sampling between 1999 and 2010 (Borges et al. 2016) and SLAM traps (2012-2016) (Borges et al. 2017). Therefore, a continuing decline in the number of mature individuals is inferred from monitoring schemes and from the ongoing habitat degradation due to invasions of alien plants (namely Hedychium gardnerianum) and a plantation of Cryptomeria japonica that was setup in the historical site, destroying most of it.

Current Population Trend: Decreasing

Habitat and Ecology

The species is restricted to a hyper-humid native forest, building the sheet weaver web in the ground between holes and the trunks of Juniperus brevifolia and Laurus azorica. The ground is also covered with mosses (with the dominance of Sphagnum spp. in some areas) and ferns. The species is active during the night.

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). Currently, invasive plants Hedychium gardnerianum and Rubus ulmifolius are dramatically changing the structure of the forest. 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). The management of surrounding habitats, namely for Cryptomeria japonica plantations, may have also an impact on individuals.

Conservation Actions

The species is not protected by regional law. However, its habitat is in a regionally protected area (Natural Park of Terceira). Degraded areas, degraded due to invasive plant species should be restored and a strategy needs to be developed to address the current threats from invasive species, and Cryptomeria japonica plantations in the Pico Alto area, and the future threat from climate change. 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 find additional specimens at more sites within the area dominated by native forest and 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).