Pannonic inland salt marshes and salt steppes (Natura 2000 habitat code 1340, 1530) belong to the priority habitats in Europe threatened by intensification of anthropogenic activities (Lubińska-Mielińska et al. 2022). These are, by definition, non-intertidal and this has a strong impact on local communities as compared to coastal salt marshes where tides act as a filter for non-resident species (as shown for example in Pétillon et al. 2004, 2010a, 2010b). In Europe, there were several studies on salt-marsh spiders, mainly in France, UK, Belgium and Germany (e.g. Ford et al. 2017, Baert & Maelfait 1999, Irmler et al. 2002). From the Pannonian biogeographical region, spiders of these habitat types were studied in Hungary (Szita et al. 1998a, 1998b, 1999, Dudás et al. 2001), Austria (Zulka et al. 1997), and at the border between Hungary and Romania (Lőrinczi et al. 2011). Only a few spider records are known from these habitats from Slovakia (Svatoň 1981, Jedličková 1988, Buchar 1999, Gajdoš 2010).

Generally, Pannonic inland salt marshes and steppes are highly influenced by the Pannonian climate with its extreme temperatures and arid summers.The enrichment of salt in the soil is due to intense evaporation of groundwater during the summer.These habitats are mostly of natural origin and partly influenced by grazing and drainage. The formation and evolution of lowland salty areas shows considerable variation in both space and time. This is strongly reflected in the present diverse morphology of salty areas – a result of the mutual effects of pedological, climatological and hydrogeological conditions (Šefferová & Stanová et al. 2008). In Europe, they are found in only a few countries in the Pannonian basin, with the largest and most diverse area in the Hortobágy in Hungary (EUNIS 2023). In Slovakia, they represent its northern enclave and are located in the Danube plain (Dítě et al. 2021). As a result of water regulation and changes in the use of the landscape since the 1960s, their area has been reduced to only 6 % (approx. 500 ha) of its previous total area (Sádovský et al. 2004, Šefferová & Stanová et al. 2008). Although only fragments remain, each of these has been declared a protected area included in the Natura 2000 framework. In recent years, they have begun to be restored by grazing, but due to the fragmentation and degradation of the vegetation, only a few sites have a high level of naturalness comparable to the sites in Hortobágy (Fehér 2017, Dítě et al. 2021).

The inventory of communities of ground-active spiders of inland salt marshes and salt steppes (habitat codes 1340, 1530) in Podunajská nížina lowland was part of the Vega Project “Research of specific landscape elements of bio-cultural landscape in Slovakia”, which was undertaken after restoration of priority habitats (2011–2017; LIFE10 NAT/ SK/000083 “Restoration of endemic Pannonic salt marshes and sand dunes in Southern Slovakia”).

The study sites were located in nine protected salt marshes included in the Natura 2000 framework. In the period 2016–2019, we collected about 10,000 individuals of spiders. Initial results revealed six species new for our fauna (Gajdoš et al. 2019). The most interesting records of rare spider species are summarized here, including the discovery of three new species for the Slovak fauna: Ozyptila sanctuaria (O. Pickard-Cambridge, 1871) Dactylopisthes digiticeps (Simon, 1881) and Pardosa tenuipes L. Koch, 1882. The main goal of the project, based on the occurrence of rare and threatened species, was to evaluate whether the investigated Pannonian salt marshes can be islands of high biodiversity within intensively used agricultural landscapes.

Material and methods

Spiders were sampled over a period of three years by pitfall trapping using five traps in one transect per single study plot. The first transect was installed at the end of 2016 (September to November) only in Bokrošské slanisko. In 2017–18 (from 3. Mar. 2017 to 15. Mar. 2018) we ran 45 pitfall traps in nine study plots (five Natura 2000 sites, Fig. 1) and in 2018–19 (Mar. 2018 to Apr. 2019) 35 pitfall traps in 7 study plots (four Natura 2000 sites, Fig. 1). The traps consisted of a plastic flower pot creating a hole in the ground, into which was fitted a removable plastic jar (diam. 11 cm) with the 4% formaldehyde solution. They were exposed throughout the whole year, also in the winter period. Specimens were identified to species level whenever possible following Nentwig et al. (2023) using the nomenclature in the WSC (2023). The importance of the localities was assessed based on the occurrence of species listed in Slovakian Red List (Gajdoš & Svatoň 2001) (Tab. 1). The list also included potentially rare species that are new to the Slovak fauna (new) and other rare species (R) with a very small area of distribution in Slovakia which were documented from Slovakia only in the last decade (i.e. after the publication of the Slovakian Red list in 2001).

Microphotographs were taken using a stereomicroscope Leica DVM6, Olympus SZX16, Nikon SMZ18 and iPhone 13mini connected to a Meopta microscope using reflected light. Digital images were combined with Zerene Stacker v. 1.04 and measurements were taken using AxioVision v. 4.6. The specimens collected by P. Gajdoš were deposited in 70% ethanol in the collection of the Institute of Landscape Ecology SAS in Nitra.

Fig. 1:

Nine studied localities of the Pannonic salt marshes. 1. Bokrošské slanisko; 2. Kamenínske slaniská; 3. Panské lúky; 4. Panské lúky – Ráczovo jazierko; 5. Šurianské slaniská; 6. Pavelské slanisko; 7. Síky; 8. Mostové, 9. Búčske slanisko (author: J. Černecký)

Characteristics of study area

The study sites were situated on Panonnic salt steppes, salt marshes (code 1530) and inland salt meadows (code 1340). The ground-active spider communities were investigated in nine study areas localized at eight Natura 2000 sites (Figs 1, 2):

Bokrošské slanisko saltmarsh (1340) – (47.7489°N, 18.2569°E, 110 m a.s.l., 10.2 ha). Remnants of the northernmost projections of Hungarian salt puztas. Saline vegetation is found only on a very small part of the site, usually in terrain depressions. The salt marshes are negatively affected by the nearby landfill.

Kamenínske slaniská saltmarshes (1340, 1530) – (47.8787°N, 18.6442°E, 110 m a.s.l., 119.44 ha). One of the largest salt meadows in Slovakia. The Pannonian endemic Limonium hungaricum Klokov and other protected flora species can be found here. The area is negatively affected by overgrowth of shrubs and non-native trees (black locust, ash) and drying of the soil. Study plot was in the Čistiny Nature Reserve.

Panskélúkymeadows(1340,1530)–(48.1028°N,18.0397°E, 116 m a.s.l.,68.71 ha).The most extensive and best-preserved Pannonic salt marsh habitats in Slovakia.

Panské lúky meadows – Ráczovo jazierko (Rácz's pond) (1530) – (48.0951°N, 18.0517°E, 112 m a.s.l., 1 ha). Salt marsh near the pond with reeds. It is the only known locality of the rare halophyte Crypsis aculeata (L.) Aiton in Slovakia. It represents only a small part of the area of Panské lúky, but it is one of the most important localities of the Pannonic salt marshes in Slovakia.

Šurianske slaniská saltmarshes (1340) – (48.0810°N, 18.122304°E, 119 m a.s.l., 169.38 ha). Well-preserved salt marsh with typical “saline eyes”, periodical pools and depressions. It is a mosaic of salt steppes, meadows and marshes, and an extensively managed hay meadow. Cirsium brachycephalum Juratzka and other protected plant species are found here.The site is surrounded by intensively managed agricultural land. Study plot was in the part Akomáň.

Fig. 2:

Habitat photos. 1. Bokrošské slanisko; 2. Kamenínske slaniská; 3. Panské lúky; 4. Panské lúky – Ráczovo jazierko; 5. Šurianské slaniská; 6. Pavelské slanisko; 7. Síky; 8. Mostové; 9. Búčske slanisko (photos: O. Majzlan)

Pavelské slanisko saltmarsh (1340) (47.7715°N, 18.0019°E, 109 m a.s.l., 18.48 ha). Salt marshes of steppe character. From one side overgrown by reed, willows, and poplars. It used to be one of the better-preserved saltmarshes, but the area has been significantly disturbed by ploughing.

Síky (1340, 1530) (48.2214°N, 17.8981°E, 120 m a.s.l., 40.17 ha) – Western Pontic, saltmarsh sandspurrey with Plantago tenuiflora Waldst. et Kit. and wall barley (largest population in Slovakia). One of the best-preserved salt marshes, managed long-term as pastures in Slovakia.

Mostové (1340) (47.7689°N, 17.9050°E, 110 m a.s.l., 22.50 ha) – A site of western Pontic steppe character, soil layers typical for undisturbed salt marshes. Halophytic vegetation of steppe character, e.g. Lythrum tribracteatum Salzm. ex Spreng (one of two sites in Slovakia). “Saline eyes” occur at the site without vegetation. It is negatively affected by gradual desalination and invasive plant species from the surrounding intensively used agricultural land.

Búčske slanisko saltmarsh (1340) (47.7928°N, 18.4250°E, 114 m a.s.l., 44.60 ha) – halophyte vegetation of steppe character; geese used to graze here in the past. It is the habitat of Apium repens (Jacq.).

Results and discussion

During the research period 2016–2019, we recorded 220 spider species belonging to 24 families (9701 ex.), which represents almost 22% of the Slovak araneofauna. Our results indicated that salt marshes are not only important for their high species richness, but also because they are inhabited by many rarely recorded and endangered species. We revealed the occurrence of 28 threatened and 18 potentially threatened species listed in the Red list of Slovakia (Gajdoš & Svatoň 2001). Another 11 faunistically important species were documented from Slovakia only recently, six of them from salt marshes (Gajdoš et al. 2019). We also collected three new species for the Slovak fauna (Dactylopisthes digiticeps, Ozyptila sanctuaria and Pardosa tenuipes). It is likely that the species P. tenuipes was merely overlooked and confused with P. proxima (C. L. Koch 1847) in Slovakia in the past. Therefore, a revision of historical collections of P. proxima is necessary.

In wet habitats, Pardosa tenuipes L. Koch, 1882 was the most abundant. This species has also been found in surrounding countries such as Czechia (Řezáč & Rothová 2021), Austria and Hungary (Isaia et al. 2018). In drier habitats Alopecosa mariae (Dahl, 1908) was abundant, which is typical of xerothermic forest-steppe habitats (Buchar & Růžička 2002). Open habitats and “salty eyes” without vegetation were abundantly inhabited by Micaria albovittata (Lucas, 1846), which is known from Slovakia from only a few localities (Gajdoš et al. 1999, Svatoň & Gajdoš 2008, Svatoň et al. 2009). Faunistically important is also the finding of Micaria rossica Thorell, 1875, which was reported from only one locality in the Malá Fatra (Svatoň 1983, 1984). The recently published species Gnaphosa rufula (L. Koch, 1866) from Slovakia (Gajdoš et al. 2019) was found so far only in the Bokroš saltmarsh.

According to Zulka et al. (1997), we recorded three halophilic species, Crustulina sticta (O. Pickard-Cambridge, 1861), Zelotes mundus (Kulczyński, 1897) and Argenna patula (Simon, 1874). Interestingly, Z. mundus has also recently been reported from salt marshes on the Atlantic coast of southwestern France (Ridel et al. 2021). Two other species, Metopobactrus deserticola Loksa, 1981 (endemic of the Pannonian region) and Gnaphosa rufula, can be included in this group because they show a strong association to xerothermic saline habitats (Gajdoš et al. 2019). The species Zodarion italicum (Canestrini, 1868), only recently published for the first time from Slovakia (Gajdoš et al. 2023), shows spreading tendencies in Europe, therefore we expect its expansion in Slovakia as well. New findings near the railway line at the locality Panské lúky may indicate its spread. Another expanding species is Zelotes tenuis (L. Koch, 1866), firstly reported from salt marshes (Gajdoš et al. 2019). Currently it is known from several anthropogenic localities, e.g. landfill in Vrakuňa (Gajdoš et al. 2023). Both these expanding species are considered as vagrant for Pannonic salt marshes.

Overall, the rare and endangered species found represent a wide spectrum of species tied to different habitat types, which are related to the humidity, light conditions and the mosaic-like character of these habitats. Spiders occurred in the xerothermic open salty pans without vegetation, through to parts with sparse vegetation, grasslands and also more humid habitats with reed stands.

Tab. 1:

List of significant species from the conservation biology point of view (listed in Gajdoš & Svatoň 2001), rare species (R, not listed in Gajdoš & Svatoň 2001) and species new to the Slovak fauna (new), CR – critically, EN – endangered, EX – extinct, R – rare, RL – Red List, VU – vulnerable, *halophilic species

Continued

New records for Slovakia

Fig. 3:

Dactylopisthes digiticeps male from Slovakia, prosoma, lateral view (photo A. Šestáková)

Fig. 4:

Dactylopisthes digiticeps, male, left palp, prolateral and ventral view (photo A. Šestáková)

Fig. 5:

Pardosa tenuipes male, dark-brown spring variant from Panské lúky – Ráczovo jazierko (Slovakia). a. dorsal view; b. ventral view; c. leg I, prolateral view (photo P. Purgat)

Fig. 6:

Pardosa tenuipes male, transitional pale variant from Bokrošské slanisko (Slovakia). a. dorsal view; b. ventral view; c. leg I (photo P. Purgat)

Fig. 7:

Pardosa tenuipes male, pale summer and autumn variant from Pavelské slanisko (Slovakia). a. dorsal view; b. ventral view; c. leg I (photo P. Purgat)

Conclusion

Our research confirms the great importance of salt marshes and salt steppes in Slovakia as habitats with a specific composition of ground-active spider communities (presence of several rare halophilic spiders) with very high species richness. In total, we found 46 red listed species and 14 faunistically important species (three of them new for the Slovak fauna). In terms of biodiversity conservation, these habitats are located exclusively in intensely used agricultural landscapes of the Danube lowlands, therefore they are important refuge for biota including spiders (i.e., precious small islands in a sea of arable land). Although the legal protection of salt marshes is substantial, that alone will not save them. Only active interventions, so-called ecological restoration, can help.

Fig. 8:

Pardosa tenuipes, male palp. a. ventral view; b. detail of embolus after extraction (photo A. Šestáková)

Fig. 9:

Ozyptila sanctuaria, male from Slovakia. a. dorsal view; b. ventral view (photo A. Šestáková)

Fig. 10:

Ozyptila sanctuaria, male left palp. a. ventro-lateral view; b. ventral view; c. retrolateral view; d. detail of tegular apophysis, retrolateral view. Scale is only for Fig. 10a (photo A. Šestáková)