Cave-dwelling Spiders Research Articles

New Insights into the Variation and Admixture of the Cave-Dwelling Spider Trogloneta yunnanensis in South China Karst.

Subterranean karst caves can contain unexpected biodiversity, but few studies related to spider population genetics have been conducted in the karst area of Southern China. In this study, we investigated the population genetic structure of Trogloneta yunnanensis (Song & Zhu, 1994) based on 73 spider samples from six underground populations in South China Karst. Population genetic structure analysis showed a clear divergence (FST > 0.9 and Nm < 0.05) among populations according to mitochondrial genes. The phylogenetic gene tree constructed by BI and ML methods recovered six geographic clades. Divergence time estimation indicated that the divergence of these six populations can be traced back to the late Pleistocene. We supposed that the geographic isolation led to the extreme population structure. According to this study and previous studies about troglobites living in this region, the subterranean habitats of the Yunnan-Guizhou Plateau may contain many organisms with similar genetic structures. The subterranean biodiversity in the karst area of Southern China needs to be re-evaluated and protected.

Systematic notes on three troglobitic Anapistula (Araneae, Symphytognathidae) spiders from China, with the descriptions of two new species.

Three cave-dwelling spider species belonging to the family Symphytognathidae Hickman, 1931, i.e., Anapistulasanjiao sp. nov. (♂♀), A.walayaku sp. nov. (♂♀), and A.panensis Lin, Tao & Li, 2013 (♂♀), are reported from southwest China. DNA sequences and detailed illustrations of the habitus, male palps and epigynes are provided, and their distributions are mapped. Their phylogenetic position within symphytognathids and relationships were tested and assessed using previously published phylogenetic analyses on symphytognathoids. The results showed that they form a clade with A.choojaiae Rivera-Quiroz, Petcharad & Miller, 2021 from Thailand.

Spatial genetic structure of Dinaric cave-dwelling spiders

Caves put strong constraints on organisms living there, which results in acquisition of variety of troglomorphic traits, most obvious ones being depigmentation and degradation of visual system (Christiansen 2012). Cave habitats are considered fragmented, and the animals living there face limited connectivity between potential habitats (Barr 1967, Bregović and Zagmajster 2016, Trontelj 2018). Additionally, once adapted to underground conditions, cave-dwellers are thought to be unable to use the surface for dispersal, thus demonstrating population dynamics similar to those of the species found in islands (Barr and Holsinger 1985). We compared the population genetic structure of several cave spider species with different biology and ecology from different caves in the Dinarides. Namely, depigmented and anophthalmic Dysderidae species which were never collected outside caves, and several species from the genus Troglohyphantes, which exhibit different levels of troglomorphisms and dependency on cave habitat (some, like T. excavatus and T. kordunlikanus, can be occasionally found in surface habitats). Additionally, Dysderidae are wandering active hunters, while all Troglohyphantes species spin webs. In our study, we applied a hybridization-capture approach, i.e., HyRAD (Suchan et al. 2016) to extract and capture DNA from historical samples. We compared the population genetic structures among the species, and studied isolation by distance, and identified contrasted genetic structures related to the biology and ecology of each species. We identified a deeper population structuring and more pronounced patterns of isolation by distance in the highly troglomorphic species compared to the less troglomorphic ones. Species that can occasionally be found in surface habitats showed less structured populations compatible with higher dispersal ability. Additionally, we detected several common breaks in gene flow for most studied species, some of which can be explained by geographic and geologic features.

A Primer on Spider Assemblages in Levantine Caves: The Neglected Subterranean Habitats of the Levant—A Biodiversity Mine

Caves share unique conditions that have led to convergent adaptations of cave-dwelling animals. In addition, local factors act as filters on regional species-pools to shape the assemblage composition of local caves. Surveys of 35 Levantine caves, distributed along a climate gradient from the mesic in the north of Israel to hyper-arid areas in the south of Israel, were conducted to test the effect of cave characteristics, location, climate, bat presence, and guano level on the spider assemblage. We found 62 spider species and assigned four species as troglobites, 28 as troglophiles, and 30 as accidentals. Precipitation, elevation, latitude, minimum temperature, and guano levels significantly affected the composition of cave-dwelling spider assemblages. Caves situated in the Mediterranean region had higher species richness and abundance, as well as more troglobite and troglophile arachnids. These discoveries contribute to the knowledge of the local arachnofauna and are important for the conservation of cave ecosystems. By comparing spider assemblages of Levantine caves to European caves, we identified gaps in the taxonomic research, focusing our efforts on spider families that may have additional cryptic or yet to be described cave-dwelling spider species. Our faunistic surveys are crucial stages for understanding the evolutionary and ecological mechanisms of arachnid speciation in Levantine caves.

Unique behavioural modifications in the web structure of the cave orb spider Meta menardi (Araneae, Tetragnathidae)

In the last decade there has been a renewed interest in the study of behavioural adaptations to environmental constraints with a focus on adaptations to challenging habitats due to their reduced ecological complexity. However, behavioural studies on organisms adapted to nutrient poor subterranean habitats are few and far between. Here, we compared both morphological traits, in terms of relative leg lengths, and behavioural traits, captured in the geometry of the spider web, between the cave-dwelling spider, Meta menardi, and two aboveground species from the same family (Tetragnathidae); Metellina mengei and Tetragnatha montana. We found that the webs of the cave spider differed significantly from the two surface-dwelling species. The most dramatic difference was the lack of frame threads with the radii in the webs instead attaching directly to the surrounding rock, but other differences in relative web size, web asymmetry and number of capture spiral threads were also found. We argue that these modifications are likely to be adaptations to allow for a novel foraging behaviour to additionally capture walking prey within the vicinity of the web. We found only limited evidence for morphological adaptations and suggest that the cave orb spider could act as a model organism for studies of behaviour in energy-poor environments.

Occurrence of the Black lace-weaver spider, Amaurobius ferox, in caves

Subterranean habitats house a wide range of species which show a number of adaptations to prevailing ecological conditions. Spiders are among the most abundant predators in caves; however, most studies on cave spiders focus on species adapted to these habitats. This is the first study related to the occurrence of the Black lace-weaver spider, Amaurobius ferox, in caves. The species lacks adaptations to the subterranean habitats and has been observed within meters from the cave entrance all year round, except in late winter until early spring. Furthermore, its occupancy is positively related to the presence of other three cave-dwelling spiders: Metellina merianae, Meta menardi and Tegenaria sp.

Local- versus broad-scale environmental drivers of continental β-diversity patterns in subterranean spider communities across Europe.

Macroecologists seek to identify drivers of community turnover (β-diversity) through broad spatial scales. However, the influence of local habitat features in driving broad-scale β-diversity patterns remains largely untested, owing to the objective challenges of associating local-scale variables to continental-framed datasets. We examined the relative contribution of local- versus broad-scale drivers of continental β-diversity patterns, using a uniquely suited dataset of cave-dwelling spider communities across Europe (35-70° latitude). Generalized dissimilarity modelling showed that geographical distance, mean annual temperature and size of the karst area in which caves occurred drove most of β-diversity, with differential contributions of each factor according to the level of subterranean specialization. Highly specialized communities were mostly influenced by geographical distance, while less specialized communities were mostly driven by mean annual temperature. Conversely, local-scale habitat features turned out to be meaningless predictors of community change, which emphasizes the idea of caves as the human accessible fraction of the extended network of fissures that more properly represents the elective habitat of the subterranean fauna. To the extent that the effect of local features turned to be inconspicuous, caves emerge as experimental model systems in which to study broad biological patterns without the confounding effect of local habitat features.

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

BackgroundSpiders (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 informationData 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° 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.

A synthesis on cave-dwelling spiders in Europe

We provide the first overview on spiders living in subterranean habitats in Europe, including the first European subterranean spider checklist. In Europe, there are 486 spider species known to dwell in caves and other subterranean habitats, distributed across 22 families. Despite a few species being able to colonize caves across the whole continent, approximately 90% of the species show a restricted distribution, occurring exclusively in one or two countries. From a biogeographic perspective, southern Europe emerges as the main hot spot of subterranean spider diversity, showing the highest richness of endemic species. Compared to other temperate regions of the world, some families appear to be well represented and other poorly represented (or lacking) in European subterranean habitats. Overall, it appears that the taxonomical knowledge on subterranean spiders in Europe is sufficient, but not evenly distributed. As this checklist represents a useful baseline for advances in this field, we point out specific areas of interest for future research.

Association of a white-banded jumping Spider 'Hypoblemum albovittatum' (Salticidae: Araneomorphae: Aranaea) with an Anemone Stinkhorn Fungus 'Aseroe rubra' (Phallaceae: Basidiomycota)

Scientists have carried out research on the sensory biology of spiders for well over a century with some interesting results. Spiders in general are known now to have a good variety and number of sensory receptors. Most spiders have eight eyes, which in some species give nearly 360 degrees vision, although other species have poor vision (e.g. Barth 2002; Framenau et al. 2014); cave-dwelling spiders may have little or no vision (Doran et al. 2001; Egan 2013; Framenau, et al. 2014). Certain spiders once were thought to be deaf (e.g. Pritchett 1904); but, some salticid spiders have a good sense of hearing, demonstrating an acoustic-triggered startle response (Shamble et al. 2016). The fact that some male salticids, e.g. Maratus species (Otto and Hill 2015), give remarkably colourful courtship displays suggests they have at least some degree of colour vision. This has been confirmed by several recent studies (e.g. Taylor 2016; Zurek et al. 2015). Salticid spiders are well-known to have elaborate vision-based predatory strategies (Cross et al. 2009; Zurek et al. 2015; Whyte and Anderson 2017). The giant-eyed Deinopidae species are also heavily dependent on vision for their net-casting behaviour (Whyte and Anderson, 2017). Spiders can discriminate between arthropod prey species, refusing to attack certain toxic species such as some cockroaches, butterflies and millipedes (pers. obs.; Vasconcellos-Neto and Lewinsohn 1984) suggesting they may have a sense of taste, although experiments by Toft (1999) suggest aversion memory is short-lived.

Modelling the future spread of native and alien congeneric species in subterranean habitats — the case of Meta cave-dwelling spiders in Great Britain

The threshold zones between the epigean and hypogean environments are generally characterized by less harsh ecological conditions than deep subterranean habitats, and usually support a greater abundance of organisms. Transitional habitats such as these should be more easily colonised by alien species, especially by those possessing exaptations suitable for subterranean life. In spite of this, few studies have been conducted to unravel the ecological dynamics between native and alien species in the habitats situated at the epigean/hypogean interface. A unique test case is offered by cave-dwelling Meta orb-weaver spiders in Great Britain (Araneae: Tetragnathidae). One species, M. menardi, is a widespread native, whilst M. bourneti is believed to be a recently introduced (1940s) species, that has since become established in the south-eastern part of the country. Species distribution models (SDM) were used to predict current and future habitat suitability for the two species, generating hypotheses regarding their distribution in different global warming scenarios. Model projections indicate that the two species respond to similar environmental variables. Seasonal temperature variations at the surface and elevation are the main factors explaining the distribution of both species, whereas annual precipitation, daily temperature range and limestone distribution contributed little to the model performance. It is predicted that due to climate change, there will be poleward shifts in the ranges of both species. However, the native species M. menardi will primarily be able to exploit suitable areas which will appear northward to their current distribution, and M. bourneti will colonise empty niches left available by its congeneric. The analytical framework employed in this paper may be easily adapted to other subterranean systems and species, stimulating future studies focusing on the distribution of native and alien species in extreme environments.

NEW FAUNISTIC DATA ON THE CAVE-DWELLING SPIDERS IN THE BALKAN PENINSULA (ARANEAE)

The contribution summarizes previously unpublished data and adds records of newly collected cave-dwelling spiders from the Balkan Peninsula. New data on the distribution of 91 species from 16 families, found in 157 (27 newly established) underground sites (caves and artificial galleries) are reported due to 337 original records. Twelve species are new to the spider fauna of the caves of the Balkan Peninsula. The species Histopona palaeolithica (Brignoli, 1971) and Hoplopholcus longipes (Spassky, 1934) are reported for the first time for the territory of Balkan Peninsula, Centromerus cavernarum (L. Koch, 1872), Diplocephalus foraminifer (O.P.-Cambridge, 1875) and Lepthyphantes notabilis Kulczyński, 1887 are new for the fauna of Bosnia and Herzegovina, Cataleptoneta detriticola Deltshev &amp; Li, 2013 is new for the fauna of Greece, Asthenargus bracianus Miller, 1938 and Centromerus europaeus (Simon, 1911) are new for the fauna of Montenegro and Syedra gracilis (Menge, 1869) is new for the fauna of Turkey. Seventy two new species records are announced for 47 caves with known spider fauna. Thus, the number of spiders established in the Balkan caves was increased up to 410 species.

Discovery of two new species of eyeless spiders within a single Hispaniola cave

Vision is a remarkable sensory adaptation; however, natural selection may not favor maintenance of eye function in habitats where eyesight does not contribute to fitness. Vision loss is relatively common in cave-dwelling spiders in the temperate zone, but appears rarer in tropical caves. To date, blind spiders in the (sub)tropical Caribbean have only been described from Cuba and Jamaica, including four pholcids, a barychelid, a ctenid, and a prodidomid with reduced eyes. In our survey of over 40 caves in the Greater Antilles, mainly Puerto Rico, Isla Mona, Cuba, and Dominican Republic, we have not previously found any eyeless spiders. Here we summarize information on blind Caribbean spiders, and describe two newly discovered species representing two families, from a single cave, Cueva Seibo, in the Dominican Republic. These are the eyeless Ciba seibo n. gen., n. sp. (Ctenidae) and the vestigial-eyed Trichopelma maddeni n. sp. (Barychelidae). Cueva Seibo appears to be an energy-poor system with a relatively small bat population and is physiologically unique amongst caves we surveyed. We postulate that troglobiomorphism in the Caribbean may result from individual cave environments and hypothesize convergent eye loss within this cave, as most members of both families, including epigean species from the Dominican Republic, have normal eyes. However, another blind species, Ciba calzada (Alayon 1985) n. comb., occurs in a cave in Cuba and it remains to be tested if eye loss occurred in these two convergently, or if their shared lack of eyes is homologous.

New cave-dwelling spiders of the family Nesticidae (Arachnida, Araneae) from China

Nine new species of the family Nesticidae, collected from caves in Guangxi, Guizhou, Henan and Yunnan Provinces of China, are diagnosed, described and illustrated: Nesticella apiculata n. sp., Nesticella arcuata n. sp., Nesticella falcata n. sp., Nesticella gracilenta n. sp., Nesticella semicircularis n. sp., Nesticella shanlinensis n. sp., Nesticella verticalis n. sp., Nesticus globosus n. sp. and Nesticus navicellatus n. sp. Nesticella mogera (Yaginuma, 1972), from Guizhou, is described and compared to the new species.

The faunistic diversity of cave-dwelling spiders (Arachnida, Araneae) of Greece

Until today, from Greek caves a total of 109 species of spiders belonging to 25 families are known. One species, the linyphiid Porrhomma convexum (Westring, 1861) was recorded here for the first time in Greece. The 109 species are distributed in caves of different geographic territories as follows: Thrace - 8 species, Macedonia - 18, Epirus - 1, Thessaly - 6, Central Greece - 3, Attiki-Saronic Islands - 24, Peloponnese - 15, Evoia-Vories Sporades - 1, Eastern Aegean Islands - 5, Cyclades - 3, Dodecanese - 6, Ionian Islands - 23, Crete - 47. The largest fraction of troglobite species were encountered mainly in the territories of Crete - 15 species (5 of which are anophthalmic), the Ionian Islands - 4, Thrace - 2 (both anophthalmic), the Attiki-Saronic Islands - 2 (both anophthalmic), the Pe- loponnese - 2 (one anophthalmic), and Macedonia, Thessaly, and the Cyclades - each with 2 species. The richness of the troglobitic spiders in these regions strengthens the assumption that they were major centres of speciation and evolution for the species of this group. According to their current distribution, the established 109 species can be classified into 12 zoogeograpical categories, grouped into 4 complexes (widely distributed, European, Mediterranean, endemics). The largest number of species belong to the endemic complex (53.2 %) and are also the most characteristic and reflect the local character of the cave-dwelling spiders.

On some leaf-litter and cave-dwelling spiders (Aranea: Arachnida) from the Republic of Macedonia

On some leaf-litter and cave-dwelling spiders (Aranea: Arachnida) from the Republic of Macedonia