IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group

Species

BackSavigniorrhipis topographicus Crespo, 2013

Savigniorrhipis topographicus Crespo, 2013

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

Countries of Occurrence:
Portugal - Azores

Archipelago(s):
Azores

Reviewer/s:
Russell, N.

Contributor/s:
Lamelas-López, L. & Mendonca, E.

Facilitators / Compilers/s:


Assessment Rationale:

Savigniorrhipis topographicus is a single-island endemic money spider species restricted to Sao Jorge island in Azores, Portugal (Crespo et al. 2013). It is a rare species, with a restricted Extent of Occurrence (EOO) (4-20 km2) and Area of Occupancy (AOO) (4-20 km²), although it is likely towards the higher end of this estimate. In the past, the species has probably strongly declined due to changes in habitat size, and 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 trampling of soil by dairy cows. The species occurs in a single patch of native forest (at Topo Nature Reserve), where it is under severe threat. Therefore, we suggest as future measures of conservation: (1) a long-term monitoring plan of the species; (2) control of invasive species, and (3) restrictions to the access of cattle to this area. The species is assessed as Critically Endangered (CR).

Geographic Range:

Savigniorrhipis topographicus is a single-island endemic money spider species restricted to Sao Jorge island in Azores, Portugal (Crespo et al. 2013), occurring in the Natural Forest Reserve of Topo (Natural Park of S. Jorge). The estimated Extent of Occurrence (EOO) is 4-20 km2 and the estimated Area of Occupancy (AOO) is 4-20 km2

Regions:
Portugal - Azores
Extent of Occurrence (EOO):
4-20 (km2)
Area of Occupancy (AOO):
4-20 (km2)
Elevation Lower Limit:
743 (m)
Elevation Upper Limit:
941 (m)
Biogeographic Realms:
Paleartic
Presence:
Extant
Origin:
Endemic Azores
Seasonality:
Resident

Population:

This is a very rare species, only known from a single sustainable subpopulation with very few individuals found during BALA project intensive sampling (Borges et al. 2016). 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 soil erosion and degradation due to soil trampling by dairy cows.

Current Population Trend: Decreasing

Habitat and Ecology

The species is restricted to a hyper-humid native forest and builds a sheet weaver web in the ground between holes and the trunks of Juniperus brevifolia and Ilex perado subsp. azorica. The ground is also covered with mosses (Sphagnum spp.) and ferns (Crespo et al. 2013). The species occurs in the same habitat of another single-island endemic Linyphid spider, Acorigone zebraneus (see Crespo et al. 2013) which is also restricted to the same native forest fragment (Topo, S. Jorge) (Borges and Wunderlich 2008). 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), and the species seems to have survived only at a single site at high elevation native forest of S. Jorge island. The main current threats are: a) the spread of an invasive plant species, Hedychium gardnerianum, which is changing the structure of the forest and the cover of bryophytes and ferns with impacts on web construction; b) the soil erosion due to trampling by dairy cattle (cattle are entering the native areas in S. Jorge island without control by the Conservation Managers). 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, however, its habitat is in a regionally protected area (Natural Park of S. Jorge). However, the Topo Natural Forest Reserve has a low level of protection (currently classified in category V of the IUCN) and is managed mainly for landscape conservation and recreation, one of the lowest protection levels. As also indicated by Crespo et al. (2013), we strongly recommend a future change to category I, a wilderness area managed mainly for wilderness protection, so that its natural features can be properly safeguarded. Degraded areas, degraded due to invasive plant species and trampling by dairy cattle, should be restored and a strategy needs to be developed to address the current threat by invasive species and cattle, and the future threat from climate change. 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 find additional specimens in other areas of native forest of S. Jorge and 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).