Species conservation profile of the alpine stenoendemic spider Vesubia jugorum (Araneae, Lycosidae) from the Maritime Alps

Vesubia jugorum (Simon, 1881) (Araneae: Lycosidae) is a large-sized wolf spider that occurs in alpine rocky areas above 2,000 m altitude. The species is stenoendemic, with a limited number of populations documented in the literature from the Maritime Alps (Italy, France). Due to the climate change, the current observed extent of occurrence (EEO 4,412 km) and the area of occupancy (AOO 835 km) are declining. 2 2 © Mammola S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Map of records (image):
-France -Italy

Basis of EOO and AOO:
Min Elevation/Depth (m):
Occurrences were used to model the current distribution of the species through a MaxEnt model in dismo R package (Hijmans et al. 2014). See  and Isaia et al. (2016) for details on modeling procedure. We estimated the extent of occurrence (EOO) and the area of occupancy (AOO) from the model, as implemented in the red R package (Cardoso 2016).
To estimate the potential variation of the EOO and AOO due to future climate change, the model was projected in the future (year 2028; i.e. 3 spider generations) according to two different representative concentration pathways, namely rcp 2.6 (low emission rate) and rcp 8.5 (high emission rate).

Justification for trend
The species inhabits rocky areas of the subnival and nival zones of the Maritime Alps. The high altitude regions are particularly vulnerable to climatic variations due to climate change, with warming rates approximately doubling the global average (Böhm et al. 2001). In consequence of temperature increase, range shifts towards higher latitudes or altitudes are expected (Bellard et al. 2012), causing a decrease in the EOO. In particular, we predict a future reduction of the EOO ranging from 24% (low emission scenario) to 41% (high emission scenario).

Justification for trend
Future forecasts based on different emission scenarios show a significant reduction in the bioclimatic range of Vesubia jugorum (details in Isaia et al. (2016)). We predict a future reduction of the AOO ranging from 12% (low emission scenario) to 32% (high emission scenario). In this perspective, it is important to take into account the connectivity of the suitable habitat, in order to provide coherent interpretations of the future trends. Suitable ecological corridors for this species would be represented by high-altitude rocky areas, which rarely occur between the Maritime Alps and the northern Alpine districts. The species is probably also limited by its low dispersal ability.

Justification for number of locations
The whole population is affected by the ongoing climate change.

Population
Unknow n -a census/estimation of the population has never been attempted.

Justification for trend
Inferred from the decline in AOO.

Justification for trend
The main subpopulation of the species is centred in Maritime Alps. This core area includes over 90% of the known localities. Two additional subpopulations are identified at the northwestern and eastern corners of the distribution range, corresponding to the Southern Cottian and Ligurian Alps, respectively. All future warming scenarios predict the extinction of the latter subpopulation.

System:
Habitat specialist: Trend in extent, area or quality?: Habitat importance:

Justification for fragmentation
Within the core area the suitable habitat is roughly continuous, with peaks and rocky areas ensuring connectivity between local populations. However, unsuitable habitat -namely grasslands at lower altitudes-reduces connectivity between subpopulations.

Habitat (narrative)
The species is restricted to alpine rocky areas above 2,000 m. These include rocky debris, boulder fields, and alpine screes (Figs 4,5).

Justification for trend
The optimal habitat for the species is not expected to undergo significant variations in the future, as touristic pressure is negligible in the high mountain peaks of the Maritime Alps. Altitudinal shifts of vegetation due to climate change may hypothetically affect the extension of the subnival zone determining small variations in the extent of high altitude rocky areas.
Major Importance

Ecology and traits (narrative)
The species is active during the warm season, from the snow melting in late June to mid September. Males are mainly found from July to August, whereas females and immatures can be found throughout the whole season. During the day, individuals can be observed wandering on the rocks. Females with cocoons build retreats under stones (see illustration in Tongiorgi (1969)), usually of 10-15 x 3cm. Preliminary data on reared individuals and estimations based on body size suggest generation length > 3-4 years.

Justification for conservation actions
Most of the species range falls within the borders of national parks, sites of community importance and special protection areas, namely Parco Naturale Alpi Marittime (Italy), Parco Naturale del Marguareis (Italy) and Parc National du Mercantour (France).
In the light of the existing threats, it is expected that the survival of the species will depend on monitoring, conservation management and translocation programmes. Ex-situ conservation should also be considered, to ensure the preservation of healthy individuals for re-introduction in suitable habitats situated to the north from the current distribution area.