A contribution to the Slovenian spider fauna – IV

. We provide a list of 171 spider species from 27 families recently recorded in Slovenia. Among them are first records of Nigma flavescens, Walckenaria alticeps, Pelecopsis parallela, Erigone autumnalis and Micaria subopaca for Slovenia and a second record of Zodarion rubidum, a species just recently added to the Slovenian spider fauna.

For instance, comparison of spider species listed in the Slovenian National spider checklist (Kostanjšek & Kuntner 2015) and the species present in the neighbouring countries uncover that most of the expected, yet missing, species in the Slovenian araneofauna most likely belong to the family Linyphiidae (Fig 1).Comprising generally smaller species often associated with colder habitats (e.g.Hagvar 1973, Relys 2000, Wiśniewski et al. 2018), the shortage of Linyphiidae in Slovenia indicates undersampling of spiders in Slovenia in general, as well as a lack of efficient sampling of cryptic habitats and habitats at higher altitudes.Several species with submediterranean distribution are also expected to be found in the south-western part of the country.Furthermore, as previous studies have revealed (e. g.Kostanjšek & Celestina 2008, Mammola et al. 2018), urban environments act as a surrogate habitat for species rarely found in nature and should not be neglected.
The last decade of araneological fieldwork in in Slovenia was mostly concentrated to »Biology Students Research Camps« (herein: biology camps) that traditionally take place in the second half of the July, resulting in sub-optimal conditions for spider research.High temperatures and low precipitation at that time impact spiders' activity and makes sampling, especially during daytime, less effective.Nevertheless, the work done at biology camps provides an unprecedented insight into the Slovenian spider fauna.In the past year, however, araneological fieldwork from biology camp was complemented with two other studies, (1) a short-term sampling at Draga pri Igu, and (2) monthly surveys of spider fauna at Škocjan Caves Park.Additionally, spiders from soil invertebrate sampling at Grebenje were handed over to us for identification.
Here we provide list of spider species collected in Slovenia during aforementioned studies and report on five new species records for the Slovenian fauna.We discuss the implications of these findings and provide recommendations for future araneological work in Slovenia.There is a significant difference in the number of species of the Linyphiidae family between the countries.Country species lists were retrieved from Spiders of Europe (Nentwig et al. 2019).Slika 1. Število zabeleženih vrst iz različnih družin v Sloveniji in sosednjih državah (AUT -Avstrija, CRO -Hrvaška, HUN -Madžarska, ITA -Italija, SLO -Slovenija).V oklepajih je navedeno število družin, zabeleženih v državi.Med državami je opaziti veliko razliko v število vrst iz družine Linyphiidae.Sezname vrst za vse države smo pridobili na spletnem portalu Spiders of Europe (Nentwig et al. 2019).

Study area
Spiders were collected in different parts of the country (see Tab. 1 for full list of examined localities) in the period from 5. 2. 2016 to 17. 5. 2018.Extensive sampling was carried out on 19. 5. 2017 as a part of »Bioblitz Slovenija 2017« (Jogan et al. 2018), held at Draga pri Igu (Localities BioBlitz-1 to , where spiders were collected in various habitats at 12 sampling sites (note that soil samples were collected prior to the event on 17. 5. 2017).Another intensive survey lasted from 19. to 29. 7. 2017, as part of the annual »Biology Students Research Camp« in the Gorenjska region (Localities RTSB17-1 to RTSB17-34).The third survey, consisting of monthly examinations of araneofauna at Škocjan Caves Regional Park, lasted from May to September 2017 (Localities PSJ-1 to .Spiders were also obtained during soil invertebrates sampling near Grebenje village in 2016 and 2017 (Localities Grebenje-1 to .The specimen of Micaria subopaca was coincidentally collected at the Department of Biology building in Ljubljana (Locality BioDept-1).

Sampling methods, identification and specimen preparation
To cover as many microhabitats as possible, a variety of sampling methods (forceps, aspirator, round sweep net, inverted leaf blower, leaf litter sifter, soil sampling) were used in targeted spider sampling.Specimens were preserved in denatured 70% ethanol.Soil samples were acquired using soil sampling probe with diameter of 21 cm and later extracted using modified Tullgren-Berlese funnels.The specimens were identified by commonly used determination keys (Roberts 1995, Oger 2016, Nentwig et al. 2019,).The identity of E. autumnalis was additionally supported by recent paper by Bellvert et al. (2018).Extraction, identification, preparation and observation of the specimens were performed at the Department of Biology of the Biotechnical Faculty, University of Ljubljana.
The epigyne of female specimens was observed with Olympus SZX7 stereomicroscope and photographed with Olympus XC30 camera.
For electron microscopic observation, the male pedipalps were briefly sonicated in ultrasonic bath PIO Sonis 2 T, air-dried, mounted on aluminium stubs and sputter-coated with platinum.The prepared samples were observed with a Jeol JSM-7500F field emission scanning electron microscope.Specimens are deposited in the Department of Biology, Biotechnical Faculty, University of Ljubljana.

Results
Altogether, 716 adult spider specimens (204 males, 511 females) belonging to 171 species from 27 families were identified (see Tab. 2 for the list of species).

Discussion
With 171 species and 27 families, the spider taxa presented in this paper covers 23% and 63% of currently known spider species and families in Slovenia, respectively.Approximately one third of the listed species belong to family Linyphiidae, which is consistent with the proportion of this family in the national spider checklist (Kostanjšek & Kuntner 2015).
Additions to the Slovenian spider fauna, including five species in the present work, confirm the proverbial 'never-finished work with the checklists' and confirm predictions on undersampled spider fauna (Kostanjšek & Kuntner 2015, Kuralt & Kostanjšek 2016) as well as need of long-term systematic surveys of the spider fauna in Slovenia.
During the sampling at Škocjan Caves Regional Park, we collected Pelecopsis parallela, a first record of this species in Slovenia.Nevertheless, finding the species in Slovenia was somehow expected as it has a wide European distribution and is also present in all neighbouring countries (Lüscher et al. 2016, Nentwig et al. 2019).
In comparison to commonly used and accessible sampling techniques for spiders inhabiting the soil surface, like pitfall traps and leaf litter sifting, the sampling of soil-dwelling spiders inhabiting cryptic habitats in lower soil horizons are much more demanding and consequently less commonly used.In these techniques, the sampling of the soil by probe is followed by time consuming extraction of animals on Tullgren-Berlese funnels, which commonly require a dedicated extraction room for efficient extraction.To diminish the deficiency in soil-dwelling spiders we recently established a collaboration with the Research Group for Animal Ecology at the Biotechnical Faculty in Ljubljana, led by dr.Ivan Kos.Since the colleagues in the group are focused in other soil invertebrates, mainly centipedes (Chilopoda), they generously donated us the spiders from the already extracted material and provided us with access to their soil sampling probes and extraction equipment.Retrieving Erigone autumnalis, a new species for Slovenian spider fauna, from soil samples, the collaboration has already proved fruitful.Considering the poor sampling of deeper soil horizons for spiders in the past, further additions to the Slovenian spider fauna can be expected from this cryptic, yet faunistically rich habitat in the future.
Finding Nigma flavescens and Walckenaria alticeps during an intensive short-term (24 hour) survey at BioBlitz 2017 event (Jogan et al. 2018) emphasizes the importance of thorough samplings in our quest to fully describe the Slovenian spider fauna.Additionally, collecting Walckenaria alticeps in leaf litter and the discovery of E. autumnalis in soil samples support the claims of soil environment being one of the last frontiers in biodiversity research (Schmidt & Keith 2010, Menta 2012, Cameron et al. 2019).
The find of Micaria subopaca in an urban environment is surprising, as Nentwig et al. (2019) note that the species is mostly found on bark of coniferous trees where it preys on ants (Svenja 2015).We thus suspect the animal was accidentally brought to the building of Department of Biology from the field.
Most of the newly recorded species were expected to be found in Slovenia, as their presence has already been confirmed in the neighbouring countries (Nentwig et al. 2019), whereas Erigone autumnalis has only been confirmed in Spain, France, Switzerland (only in Tessin), Austria, Italy and Georgia.Nentwig et al. (2019) note that E. autumnalis is an alien species originating from North America and has been introduced to Europe on several occasions.Finding multiple animals in soil samples from a relatively small sampling area in Grebenje village suggest that the species has probably been overlooked.
Apart from being an important faunistic contribution as the second record of the species for the Slovenian fauna, the collection of Zodarion rubidum in the urban environment of the village Predoslje in NW Slovenia itself carries some implications that warrant discussion.The first record of Z. rubidum in Slovenia was recently reported by Kuralt & Kostanjšek (2016) from the Bela krajina region where a single female was collected in an urban environment during night-time sampling.Such isolated localities of the species were previously reported from Poland (Rozwałka & Gosik 2006), where collection site lay more than 400 km from other known localities.Nentwig et al. (2019) report that the species has been showing some spreading tendencies over the last decades, presumably facilitated by human activity (Rozwałka & Gosik 2006 and references therein), which could partially explain recent findings of the species in the country.At the same time, we should bear in mind that Z. rubidum is a nocturnal species (Pekár & Křál 2002), and that it might have been simply overlooked in previous, predominantly daytime sampling routine.
Survey of spider samplings in Slovenia quickly reveals a considerable bias towards daytime sampling of relatively accessible natural environments and little sampling effort.Considering the facts that (1) the majority of spider species are nocturnal (Foelix 2011), (2) semi-natural and urban habitats often act as surrogate habitats for species that are rarely found in natural environments (Kostanjšek & Celestina 2008, Mammola et al. 2018) and (3) cryptic and hardly accessible habitats provide niches for rarely found species, the future samplings in Slovenia should focus on temporally and spatially more evenly distributed samplings and application of sampling techniques, covering various cryptic or undersampled habitats, to ensure further additions to the Slovenian spider fauna.

Table 2 .
Species list of the examined spiders.New records for the Slovenian fauna are marked with an asterisk.For abbreviations of localities see Tab. 1. Numbers next to gender symbol refer to number of collected individuals.Tabela 2. Seznam zabeleženih vrst pajkov.Prve najdbe za Slovenijo so označene z zvezdico.Natančen opis lokalitet je v Tab. 1. V oklepajih je navedeno število in spol ujetih in določenih pajkov.