An updated checklist of spiders (Arachnida: Araneae) of Left-Bank Ukraine

Abstract. The current checklist of spiders from Left-Bank Ukraine includes 741 species in 270 genera and 34 families. The families Linyphiidae (215 species, 29% of the fauna), Gnaphosidae (83 species, 11%) and Salticidae (79 species, 11%) are the most species-rich. The Linyphiidae species diversity declines from north to south – from 33% of the fauna in the forest zone to 16% of the fauna in the bunchgrass steppe subzone. In contrast, the proportion of Gnaphosidae increases from 7% to 13%, respectively. A total of 407 spider species was recorded from the forest natural zone, 515 species from the forest-steppe, 583 species from the forb-bunchgrass steppe subzone of the steppe zone and 375 species from the bunchgrass steppe subzone. In terms of administrative division, the araneofauna of the Donetsk Region is the richest with 514 species, the faunas of the Kharkiv (426 species), Luhansk (402 species) and Chernihov (391 species) regions follow it. The poorest is the Zaporizhzhia Region with 122 species. In total, spiders have been collected at 269 localities and the results have been published in 369 papers. Faunistic and ecological studies are the main directions of arachnological research in Left-Bank Ukraine.

The araneofauna of Ukraine has been studied unevenly. The latest total list based on the state of knowledge up to 2011 made reference to 1008 species including 537 species record ed from the Ukrainian Carpathians and 520 species from the Crimea (Mikhailov 2013). Since that time, a catalogue of the spiders of LeftBank Ukraine has been published (Polchani nova & Prokopenko 2013, and a checklist of spiders from the Crimea has been updated (Kovblyuk & Kastrygina 2015). A conservation status was assessed for 386 species from the Ukrainian Carpathians (Gajdoš et al. 2014), but a com plete detailed list of the spiders from this region still needs to be compiled. The rest of Ukraine remains poorly investigated. The presentday list of Ukrainian spiders as part of the total European list accounts for 1049 species (Nentwig et al. 2018).
The catalogue of the spiders of LeftBank Ukraine con tains information on the history of study as well as published and original records supported by collection material, a list of erroneous and doubtful records, synonymies, geographic coordinates of collecting localities, general geographic distri bution and species habitat preferences within the natural zo nes and subzones. The first catalogue listed 709 spider species in 247 genera and 35 families (Polchaninova & Prokopenko 2013). Four years later, Addendum I enlarged this list to 728 species of 266 genera (Polchaninova & Prokopenko 2017). The analysed data covered the period from 1836 to 2016, and included species collected in 263 localities.
Nevertheless, new finds and changes in nomenclature over the past two years have required data revision, reexamination of some items from personal and museum collections, and updating of the total list. The purpose of the present paper is to summarize the state of knowledge of the spiders of Left Bank Ukraine, to make a checklist based on species zonal distribution, and to outline prospective directions for future studies.

Material and methods
LeftBank Ukraine is defined as the part of Ukraine east of the Dnieper River. Its total area covers more than 200 thousand square kilometres. Traditionally, the plain territory of the country is divided into the right and leftbank parts along the Dnieper flow, which is justified both historically and biogeographically (Fig. 1). LeftBank Ukraine encom passes the southwestern part of the Central Russian Upland as well as western and central parts of the Donetsk Ridge, which are both low altitude hills on the East European Plain. The study area lies in three natural zones: forest, foreststeppe and steppe (Fig. 2). The steppe zone, in its turn, is divided into three subzones: forbbunchgrass steppes (forbfescuefeather grass), bunchgrass steppes (fescuefeather grass) and sage brushbunchgrass, or semidesert steppes (sagebrushfescue feather grass). The borders of the zones/subzones presented on the map are adopted from geobotanical regioning of Uk raine (Barbarych 1977, Didukh & ShelyagSosonko 2003. The checklist of species is organized as a table, which pro vides records from the administrative regions of LeftBank Ukraine and references to the summary surveys (Tab. 1, elec tronic appendix). The regions are arranged from northwest to southeast within the natural zones. Some of the regions are mentioned twice as they are located in two neighbouring zones. Species are given alphabetically by family and then by genera within the families, the nomenclature following the World Spider Catalogue (WSC 2018). Numbers in paren thesis show the number of species in each family in the cor responding zones/subzones, and in the study area as a whole.
We marked with three exclamation marks (!!!) species registe red for the first time in Ukraine, with (!!) species registered for the first time in LeftBank Ukraine, and with (!) species cited in literature as new to LeftBank Ukraine in 2017, i.e. after the issue of the Catalogue and Addendum I (Polchaninova & Prokopenko 2013. We marked boundaries of the species' geographic ranges by a letter in case they are running through the study area: N -northern, NW -northwestern, W -western, NE -northeastern, E -eastern, S -southern, SE -southeastern, and SW -southwestern, intr -introdu ced. The list is based on original and literaturederived data that can be checked on the available collection materials.
If a species was recorded from material in a lost collection (or lost individuals from available collections) and its finding had not been proved later by other authors, we referred it to the category "need confirmation". A list of such species is gi ven separately after the main species list. We also compiled a list of erroneous records based on misidentifications. Seven species were mentioned in both "erroneous" and "doubtful" lists since their misidentifications were proved for some lo calities, but remained unconfirmed for the others (Table 2, 3, electronic appendix). The rationale for the exclusion of these species from the main list is given in the Catalogue and Ad dendum I (Polchaninova & Prokopenko 2013. Species distribution is given based on Mikhailov (2013)

Results
To date, 741 spider species from 270 genera and 34 families have been recorded from LeftBank Ukraine. The number of families has decreased compared with the previous list, since Argyroneta, the only regional genus in Cybaeidae, was transferred to the family Dictynidae. Thus, Cybaeidae was excluded from the araneofauna of LeftBank Ukraine. The following genera are the most speciose:  (Ponomarev et al. 2017) after the publication of the Addendum I of the catalogue, and are now added to the general list. Ostearius melanopygius and Heliophanus kochii were absent in the 2013 catalogue, Gnaphosa rufula and Dys dera longirostris were restored to the list from the doubtful records, and Gnaphosa dolanskyi was distinguished from G. modestior and described as new to science (Řezáč et al. 2018). Thus, the previous list has been replenished with 15 species. On the other hand, G. modestior and G. moesta have been excluded, so the list of erroneous records now comprises 41 species while that of doubtful records accounts for 47 species.
The family Linyphiidae is the most speciesrich in Left Bank Ukraine (215 species, 29% of the fauna), with Gnapho sidae and Salticidae following it (83 and 79 species, respec tively, about 11% each). The ratio of families changes from north to south across zones and subzones (Fig. 3). The pro portion of Linyphiidae declines from 33% in the forest zone to 16% in the bunchgrass steppe subzone (steppe II). In con trast, the ratio of Gnaphosidae grows from 7% in the forest zone to 13% in the steppe subzones. Fluctuation of the relati ve species richness of other families is not so evident. Diversi ty of major spider families is the most even in the bunchgrass steppe subzone (steppe II) due to the lower ratio of Linyphi idae (Fig. 3). The sagebrushbunchgrass steppe subzone has not been analyzed here because of the lack of sufficient data on its spider fauna.
The richest is the araneofauna of the steppe I (583 spe cies). All major families, except Linyphiidae, are the most di verse there (Table 1). The steppe II is the poorest (375 spider  29 species (7% of the zonal fauna) in the forest zone, 41 species (7.9%) in the foreststeppe, 69 species (12 %) in the steppe I, and 24 species (6.4%) in the steppe II. Concerning administra tive divisions, the largest number of spider species has been re gistered in Donetsk Region (Fig. 4). The number of species in the other six regions completely (or almost completely) located within LeftBank Ukraine ranges from 122 to 426.
There are no endemics in the study area. Nevertheless, the boundaries of geographic ranges of a number of species run through its territory. They are mostly northern (47 species) and western (25 species) boundaries. Besides, twelve species have eastern margins of their areas, two species northeastern, four species northwestern, two species southwestern, and three species southern margins (Table 1) Over the entire period of arachnological research in Left Bank Ukraine (since 1836 to the present day), 369 papers based on original material and/or museum collections have been published. The faunistic data were summarized in regio nal species lists, key books and/or catalogues; the most signifi cant of them were compiled by Kharitonov (1932), Mikhailov (1997 and Polchaninova & Prokopenko (2013. The first period of the records' accumulation lasted over 130 years, with no more than one or two papers published a year (Fig. 5). There were only 185 species known from the study area until early 1970s, when interest in spiders increased and resulted in publications of some local species lists. By 1990, the total list of spiders had accounted for about 350 species.    Spiders of transformed lands have been studied mainly in urban ecosystems (33 papers), reclaimed coalmine was te banks, oil drilling sites and/or ash damps of waterpower plants (16 papers). The araneofauna of Donetsk City is inves tigated best (257 species) (Prokopenko 2013). For the city of Kharkiv, the largest city in the study area, only 160 spider spe cies are known (Polchaninova & Prokopenko 2013). Despite the fact that agricultural lands occupy vast areas in LeftBank Ukraine, they are almost neglected in terms of spider studies (nine papers only). Fourteen papers deal with a role of spiders in food webs as predators and prey in natural and manmade ecosystems; nine papers discuss biological aspects of indivi dual spider species.
Systematics studies in LeftBank Ukraine (69 papers) include descriptions of new species and/or genera revisions, which use spider specimens collected in the study area as comparative material (see Kovblyuk 2005, Kovblyuk & Na dolny 2007, Kovblyuk et al. 2012. Twentysix species from the presentday territory of Ukraine were described as new to science and 17 of them are valid. Only the family Dysde ridae (Kovblyuk et al. 2008) and the genus Sintula (Gnelitsa 2012) have been surveyed in the whole of Ukraine. However, both taxa are poor in the leftbank area (six and two species, respectively).

Discussion
Despite the long history of research, the spider fauna of Left Bank Ukraine is still far from being well studied. The number of registered species (741) is lower than in other countries in eastern or easterncentral Europe, regardless of their area (Nentwig et al. 2018): e.g., Bulgaria (110994 km 2 ) -1038 species, Romania (238397 km 2 ) -1007, Slovakia (49035 km 2 ) -980, Czech Republic (78865 km 2 ) -888, Poland (312679 km 2 ) -847 and Hungary (93030 km 2 ) -804. The area of LeftBank Ukraine is approximately 242 088 km 2 . However, the relatively poor faunistic list can be explained not only by the insufficient data but also by the plain landscape of the study area. The adjacent region of Central European Russia also hosts only 698 species (Mikhailov 2013, Nentwig et al. 2018. The lack of geographically detached regions results in the lack of endemic spiders. Though the Donetsk Ridge, lo cated mainly within LeftBank Ukraine, is an endemic area for a number of plant species (Didukh 2009), spiders with the similar geographic ranges are not known.
The araneofauna of the forbbunchgrass steppe subzone is the richest in LeftBank Ukraine. This was to be expected gi ven its large area, variety of climatic conditions, and the high est habitat diversity -from floodplain forests in the north to dry steppes and seashore in the south. Moreover, it hosts the largest number of protected areas and has been best studied. The administrative regions of LeftBank Ukraine remain un equally inventoried. Only the fauna of the Donetsk Region (514 species) can be considered sufficiently studied. We can compare it with the araneofauna of the adjacent Rostovon Don Region of Russia, which accounts for about 600 spider 1 9 7 1 1 9 8 9 1 9 9 3 1 9 9 7 1 9 8 1 1 9 4 0 1 8 9 7 1 8 8 1 1 8 6 6 1 9 3 2 2 0 0 1 1 9 7 6 1 9 8 5 2 0 0 5 2 0 0 9 2 0 1 7 2 0 1 3 1 8 3 6 species (Ponomarev 2005, Ponomarev et al. 2016). Yet here we have to take into consideration that the Rostov Re gion is four times larger and includes an area of semidesert steppes absent in the Donetsk Region. The worst studied in LeftBank Ukraine are the Zaporizhzhia and Poltava regions.
There is a huge gap in arachnological taxonomic studies in both LeftBank Ukraine and Ukraine as a whole. Per manent systematic research is being conducted only in the Crimea, mainly in the families Gnaphosidae, Philodromidae, Linyphiidae, and superfamily Lycosoidea (Gnelitsa 2009, Kovblyuk et al. 2012, Kastrygina & Kovblyuk 2013, 2014, Nadolny 2014. The Linyphiidae is under study throughout Ukraine (V. Gnelitsa's research), but the results have not been summarized yet.