Spiders in caves: the CAWEB project

World experts of different disciplines, from molecular biology to macroecology, recognize the value of cave ecosystems as ideal ecological and evolutionary laboratories. Among other subterranean taxa, spiders stand out as intriguing model organisms for their ecological role of top-predators, their unique adaptations to the hypogean medium and their sensitivity to anthropogenic disturbance. Here, we provide a general overview of the spider families recorded in hypogean habitats in Europe–20 families including nearly 500 species, most of them with restricted distributions. We also review the different adaptations of hypogean spiders to subterranean life and summarize the information gathered so far about their origin, population structure, ecology and conservation status. Taxonomic knowledge on subterranean spiders in Europe appears to be well, but not exhaustively documented. The origin of the European assemblages is mostly explained by past climate dynamics, although other factors are likely to be involved. Most of the macroecological issues related to spiders in European caves are based on qualitative assessments or have been quantified only at a sub-regional scale. In order to shed light on cave spiders’ biogeography and the macroecological patterns driving the diversity of European subterranean spiders we created the CAWEB network, a spontaneous collaboration between subterranean arachnologists from 30 different European countries. We here present the team and provide some preliminary results, which highlight Southern Europe as an important hot-spot for the European subterranean spider diversity

Continental data on cave-dwelling spider communities across Europe (Arachnida: Araneae)

Background Spiders (Arachnida: Araneae) are widespread in subterranean ecosystems worldwide and represent an important component of subterranean trophic webs. Yet, global-scale diversity patterns of subterranean spiders are still mostly unknown. In the frame of the CAWEB project, a European joint network of cave arachnologists, we collected data on cave dwelling spider communities across Europe in order to explore their continental diversity patterns. Two main datasets were compiled: one listing all subterranean spider species recorded in numerous subterranean localities across Europe and another with high resolution data about the subterranean habitat in which they were collected. From these two datasets, we further generated a third dataset with individual geo-referenced occurrence records for all these species. New information Data from 475 geo-referenced subterranean localities (caves, mines and other artificial subterranean sites, interstitial habitats) are herein made available. For each subterranean locality, information about the composition of the spider community is provided, along with local geomorphological and habitat features. Altogether, these communities account for > 300 unique taxonomic entities and 2,091 unique geo-referenced occurrence records, that are made available via the Global Biodiversity Information Facility (GBIF) (Mammola and Cardoso 2019). This dataset is unique in that it covers both a large geographic extent (from 35 south to 67 degrees north) and contains high-resolution local data on geomorphological and habitat features. Given that this kind of high-resolution data are rarely associated with broad-scale datasets used in macroecology, this dataset has high potential for helping researchers in tackling a range of biogeographical and macroecological questions, not necessarily uniquely related to arachnology or subterranean biology

UNA NUOVA STRAORDINARIA SPECIE DEL GENERE DYSDERA DELL’ITALIA MERIDIONALE (ARANEAE, DYSDERIDAE)

Dysdera aberrans n. sp. (♂♀) viene descritta su esemplari raccolti presso Casacalenda (Campobasso). La nuova specie presenta caratteristiche assolutamente peculiari, in particolare per quanto riguarda la morfologia degli organi genitali maschili, che non ne consentono la collocazione in alcuno dei gruppi istituiti per ospitare le 250 specie congeneri sinora conosciute

A new cave-dwelling Centromerus from Sardinia (Araneae: Linyphiidae)

Centromerus marciai sp. n. is described on both sexes on specimens collected in a karstic cave in the province of Nuoro, North-eastern Sardinia, Italy. Differences with other species of the genus Centromerus Dahl, 1886 occurring in Sardinia are pointed out

DESCRIZIONE DI DYSDERA ROMANA N. SP. DEL LAZIO (ARANEAE, DYSDERIDAE)

Dysdera romana n. sp. viene descritta su esemplari raccolti in quattro località situate nei dintorni di Roma. La nuova specie appartiene al gruppo crocota ed è riconoscibile in base alla morfologia degli organi genitali

Systematics and phylogeography of the Dysdera erythrina species complex (Araneae, Dysderidae) in Sardinia

Volume: 16Start Page: 319End Page: 34

Systematics and phylogeography of the Dysdera erythrina species complex (Araneae, Dysderidae) in Sardinia

Sardinia is the second largest island in the Mediterranean and, together with Corsica and nearby mainland areas, one of the top biodiversity hotspots in the region. The origin of Sardinia traces back to the opening of the western Mediterranean in the late Oligocene. This geological event and the subsequent Messinian Salinity Crisis and Pleistocene glacial cycles have had a major impact on local biodiversity. The Dysdera woodlouse hunter spiders are one of the most diverse ground-dweller groups in the Mediterranean. Here we describe the first two species of this genus endemic to Sardinia: Dysdera jana sp. n. and Dysdera shardana sp. n. The two species show contrasting allopatric distribution: D. jana sp. n. is a narrow endemic while D. shardana sp. n. is distributed throughout most of the island. A multi-gene DNA sequence phylogenetic analys based on mitochondrial and nuclear genes supports the close relationships of the new species to the type species of the genus Dysdera erythrina. Age estimates reject Oligocene origin of the new Dysdera species and identify the Messinian Salinity Crises as the most plausible period for the split between Sardinian endemics and their closest relatives. Phylogeographic analysis reveals deep genetic divergences and population structure in Dysdera shardana sp. n., suggesting that restriction to gene flow probably due to environmental factors could explain local speciation events

Systematics and phylogeography of the Dysdera erythrina species complex (Araneae, Dysderidae) in Sardinia

Sardinia is the second largest island in the Mediterranean and, together with Corsica and nearby mainland areas, one of the top biodiversity hotspots in the region. The origin of Sardinia traces back to the opening of the western Mediterranean in the late Oligocene. This geological event and the subsequent Messinian Salinity Crisis and Pleistocene glacial cycles have had a major impact on local biodiversity. The Dysdera woodlouse hunter spiders are one of the most diverse ground-dweller groups in the Mediterranean. Here we describe the first two species of this genus endemic to Sardinia: Dysdera jana sp. n. and Dysdera shardana sp. n. The two species show contrasting allopatric distribution: D. jana sp. n. is a narrow endemic while D. shardana sp. n. is distributed throughout most of the island. A multi-gene DNA sequence phylogenetic analys based on mitochondrial and nuclear genes supports the close relationships of the new species to the type species of the genus Dysdera erythrina. Age estimates reject Oligocene origin of the new Dysdera species and identify the Messinian Salinity Crises as the most plausible period for the split between Sardinian endemics and their closest relatives. Phylogeographic analysis reveals deep genetic divergences and population structure in Dysdera shardana sp. n., suggesting that restriction to gene flow probably due to environmental factors could explain local speciation events