Isotomidae, Schaffer, 1896

Antipova, M. D. & Babenko, A. B., 2022, An annotated checklist of the springtails (Hexapoda: Collembola) recorded from the foothill and mountain parts of the Republic of North Ossetia-Alania, North Caucasus, Russia, Russian Entomological Journal 31 (4), pp. 331-345 : 337-339

Family Isotomidae

Anurophorus alpinus Potapov et Stebaeva, 1990 . A montane species described from the nature reserve (Tsey Gorge). It is widely distributed in the North Caucasus, often reaching high densities. There are also records available from Dagestan and the Swiss Alps [ Potapov, 1997]. In the nature reserve, it tends to occur in the moss-lichen cover on rocks and moraines, often being dominant [ Kuchiev, 1984, referred to as A. laricis Nicolet, 1842 ; Kuchiev, 2006].

* A. palearcticus Potapov, 1997 . A boreal species distributed in the northern and eastern parts of European Russia, all of Siberia up to the Far East and Mongolia. In the Caucasus, the species is known from Kabardino-Balkaria [ Potapov, 2001] and the environs of Sochi [ Scherbina, 2020]. In the North Ossetian Nature Reserve it has been found for the first time (Tsey Gorge) and collected from the moss-lichen cover of moraine stones, where it usually prevailed in abundance over A. alpinus .

Ballistura sp. In our material, there are only two specimens of the genus, both collected on an almost bare rocky surface, one freed from ice only 4 years earlier. An exact identification of these specimens is difficult. Among the known European congeners, it is seems to be the closest to B. albertinae Ellis, 1976 by a similar structure of the furca, but it is easily distinguishable by the absence of a tooth on the claw. Kuchiev (1984) seems to have referred to this particular form as Proisotoma sp. , as one of the dominants in plant communities on the rocks of the eastern slopes of Kalper Peak (3500 m a.s.l.).

** Desoria sp. aff. duodecimoculata Denis, 1927. Most likely, this is a new species belonging to the alpine nivaliscomplex [see Potapov, 2001], which is common in the European highlands. The identity is possible to establish only upon a complete revision of the European congeners of this complex. In the nature reserve, it has been encountered exclusively inside a bare ground at the edge of Tsey Glacier This seems to be a member of a unique glacial complex of springtails inhabiting exclusively areas in the affinity to glaciers. It is probable that Isotoma nivalis (Carl, 1910) , listed by Kuchiev [2006] as an inhabitant of high mountains of the nature reserve, is actually a representative of this species.

** D. fennica (Reuter, 1895) . A hygrophilous species with a wide Palaearctic distribution. This is the first record of this species from North Ossetia (vicinity of Fazikau, close to Dargavs collected by O.L. Makarova) .

** D. grisea (Lubbock 1870) . A member of the genus widespread throughout Europe, usually associated with decaying plant material of both natural and anthropogenic origin. It has not been recorded from North Ossetia before. In our collections from the Tsey Gorge , there is only one specimen of this species, collected in a maple forest .

** Desoria nivea (Schäffer, 1896) . A European species collected under the bark and in the litter of the upper part of Tsey Gorge. The specimens found were identical to the summer form of the real D. nivea . Yet it is distinguished by the presence of a weak diffuse pigment throughout the body (even in juveniles) and the absence of any pronounced facets along with maintaining the colour of the ocelli. Nevertheless, M. Potapov (personal communication) confirmed the species identity of these individuals as representing the true D. nivea , which morphs, as it turns out, can be eyeless indeed.

Desoria cf. tolya Fjellberg, 2007 . The presence of this northern European species in such a southern region definitely requires confirmation. Unfortunately, our material contains only a single juvenile specimen. The record of Isotoma violacea ( D. violacea at present) from the pine-birch forests of Tsey Gorge (1750 m a.s.l.) [ Kuchiev, 2006] supposedly belongs to this species. There is also evidence on the presence of the other congeners in the republic [ Kremenitsa, 2002; Kuchiev, 2006, sub Isotoma olivacea Tullb. ]. The species identity of these records remains unknown.

Folsomia alpina Kseneman, 1936 . A European alpine species common in the highland forests of the Caucasus, Carpathians and Alps. It was recorded from the alpine belt of the nature reserve at altitudes over 3000 m [ Kuchiev, 2006], where rarely reached high density levels. We have found one specimen each on a lateral moraine of the Skazsky Glacier at an altitude of ~ 2400 m s.a.l. and at the meadow overgrowing stage in the Tsey foreland at an altitude of 2300 m s.a.l.

F. inoculata Stach, 1947 . A widespread montane species distributed almost throughout the Palaearctic and the Pacific coast of North America [ Potapov et al., 2018]. In the North Ossetian Nature Reserve, this species is quite common [ Kuchiev, 2006]. Kuznetsova et al. [2019] record- ed it from a pine forest near the village of Nar. In our material, the species was abundant in a beech forest at an altitude of 1865 m a.s.l.

F. litsteri Bagnall, 1939 . A European species mainly confined to forest litter [ Potapov, 2001, referred to as F. lawrencei Rusek, 1984 ]. In the European part of Russia, it is common in anthropogenic landscapes, probably introduced [ Kuznetsova, 1995, sub F. lawrencei Rusek, 1984 ]. In the nature reserve, it was earlier recorded from pine forests [ Kuznetsova et al., 2019]. In the Tsey Gorge, we have encountered the species in a birch forest (2240 m a.s.l.), a mixed pine forest and a blueberry pine forest (2070–2205 m a.s.l.), especially abundant in a beech forest at 1865 m a.s.l.

* F. manolachei Bagnall, 1939 . An eurytopic species. In our collections, it has been found in two places: at the shrub stage of overgrowing in the Tsey foreland and in a young mixed forest with rich herbs (2295 m and 2250 m a.s.l., respectively).

F. penicula Bagnall, 1939 . A mesophilic forest species from the spinosa -group, distributed almost throughout Europe, known also from North America [ Potapov, 2001]. Abundant in mountain rendzinas of the Carpathians [ Rusek 1993, 1996]. In the eastern Alps, it was recorded only from subalpine coniferous woods [Kopezski, Meyer, 1996]. In the Caucasus, including North Ossetia was first listed by Stach [1947] and [ Kuchiev, 2006], sub F. multiseta (Stach, 1945) , also found in a pine forest near the village of Nar [ Kuznetsova et al., 2019].

F. ksenemani Stach, 1947 . Another representative of the spinosa -group. Due to unclear distinguishing features largely depending on age, in the fauna of the Caucasus the species has usually appeared under the name F. pseudodiplophthalma Stach, 1947 [ Dobrolyubova, 1984a; Kuznetsova et al., 2019]. At present, these two species considered synonyms [Poinsot, 1972; Potapov, 2001]. In the nature reserve, the species was recorded by Kuchiev [1984, 2006, in the latter paper referred to as F. diplophthalma and perhaps F. spinosa as well] and later also from the vicinity of the village of Nar [ Kuznetsova et al., 2019]. Based on our material, F. ksenemani is common in the belt of pine forests of the Tsey Gorge. In the foreland, it appears first in a forb shrub community (a 14- year old surface since the glacier’s retreat).

F. quadrioculata (Tullberg, 1871) . A Holarctic polyzonal species characterized by the absence of obvious habitat preferences. It was recorded from the republic earlier [ Kuchiev, 1984, 2006; Kuznetsova et al., 2019]. Based on our material, it occurs in a wide range of habitats in the Tsey Gorge, often together with F. manolachei , in fairly large abundance.

Folsomides parvulus Stach, 1922 . A xerophilic and psammophilic cosmopolitan of soils in open habitats. In North Ossetia, it was recorded from a pasture located east of Alagir [ Kremenitsa, 2002]. Our data confirm the xerophile status of this species, because we have found it in two rather dry areas: the herbaceous and shrubby stage of overgrowth of the postglacial surface.

Hemisotoma orientalis ( Stach, 1947) . A xerothermic species. In North Ossetia, it was known from the collections of A.M. Kremenitsa (as a species of the genus Cryptopygus ) in a pasture located east of Alagir [ Kremenitsa, 2002] .

H. pontica ( Stach, 1947) . A xerothermic and ruderal species distributed in the Palaearctic. It was recorded by the same author on the same sampling plot [ Kremenitsa, 2002].

H. thermophila (Axelson, 1900) . A thermophilic and nitrophilic cosmopolitan [ Potapov, 2001]. It was recorded from North Ossetia as a species of the genus Cryptopygus [ Kremenitsa, 2002]. In our material from the Tsey Gorge, it has been found in a pine forest with admixture of birch and rhododendron at 2205 m a.s.l.

Hydroisotoma schaefferi (Krausbauer, 1898) . A neuston species common in Europe and South America. From the Caucasus ( Georgia), it was first recorded by Stach [1947], while from North Ossetia by Potapov [2001], the latter record originate from the outskirts of Alagir. According to Kuchiev [2006], the species is widespread on the northern macro slope of the Caucasus from valley alder forests to mid-mountain pine woodlands.

Isotoma viridis Bourlet, 1839 . One of the most common and polytopic species in the Holarctic. In the nature reserve, it was first found on Mount Kalper at an altitude of 3500– 3800 m a.s.l. [ Kuchiev, 1984, 2006]. It was also recorded as a subdominant on a perennial pasture near Alagir [ Kremenitsa, 2002]. In the Tsey Gorge, we have found it in forests of different ages (areas 34–96 years after the glacier’s retreat), 2200–2250 m a.s.l.

Isotomiella minor (Schäffer, 1896) . The species has been recorded all over the world, but most likely it occurs only in the temperate zone of the Holarctic [ Potapov, 2001]. In the nature reserve it is quite abundant [ Kuchiev, 2006; Kuznetsova et al., 2019]. Based on our material, in the Tsey Gorge the species is mainly confined to forest communities, where it is often dominant. Along the successional series, this species has appeared in a developed birch forest (2244 m a.s.l.), where it immediately reached high density. Farther down the slope, the species retained high density, occasionally yielding only to Parisotoma notabilis .

Isotomodella alticola (Bagnall, 1949) . A predominantly northern Palaearctic species, the southern records of which, including North Ossetia [ Kremenitsa, 2002, referred to as Pseudanurophorus cf. inoculatus ] clearly require clarification .

Isotomodes productus (Axelson, 1906) . A cosmopolitan species of dry open spaces, usually not reaching high abundance levels [ Potapov, 2001], even though in North Ossetia it was recorded as a subdominant from pastures near Alagir [ Kremenitsa, 2002].

** Isotomurus sp. No species of this genus have previously been recorded from the republic. Obviously, this is due to the poor knowledge of hydromorphic habitats of the region. Unfortunately, our material from the Tsey Gorge contains only one immature individual and its identification is impossible. The most notable feature of this individual is elongated claws (especially on the first and second pairs of legs). Several undetermined individuals were also recorded from the vicinity of Verkhny Fiagdon (collection of O.L. Makarova).

Pachyotoma caucasica ( Stach, 1947) . The species was described from Transcaucasia ( Georgia), but it is also known from the Alps ( Italy) [ Dallai, 1970]. From North Ossetia, it was recorded by Potapov [2001], possibly based on the collections of I.T. Kuchiev from Mount Kalper [1984, referred to as Proisotoma sp. ].

** P. crassicauda (Tullberg, 1871) . Several juvenile specimens have been found in our material from the Tsey Gorge (a birch forest in the upper part of the forest belt, near a temporary stream, 2244 m a.s.l.).

Parisotoma notabilis (Schäffer, 1896) . The species is considered cosmopolitan. It seems to occur almost everywhere in the republic [ Kuchiev, 1984, 2006, Kremenitsa, 2002, Kuznetsova et al., 2019]. Based on our material, P. notabilis colonizes the Tsey foreland at the shrub stage, quickly reaching high abundance levels and becoming a dominant in the forest belt.

Parisotoma sp. An undetermined species of the genus, found in the collections of Kuznetsova et al. [2019] from a pine forest of the Tsey Gorge. It is characterized by the presence of 1+1 large ocelli, 3+3 postlabial setae, VT with 2+2 lateral setae, and the absence of setae on the lower subcoxa of the first pair of legs. Unfortunately, there is only one immature individual in this material.

** Proisotoma minima Absolon, 1901 . A widespread Holarctic species. The available South American records require confirmation. The species usually lives under bark and is rare in the forest litter. This is the first record from North Ossetia: only a few individuals in a mature forest of the Tsey Gorge.

P. minuta (Tullberg, 1871) . A thermophilic ruderal cosmopolitan, common in composts. In North Ossetia, it was recorded from near Alagir [ Kremenitsa, 2002]. In the Tsey foreland, it has been found in a birch forest (2244 m a.s.l.) and in a lower maple forest (1984 m a.s.l.) .

Pseudanurophorus binoculatus Kseneman, 1934 . A Holarctic boreo-montane species. In the nature reserve, it was recorded from a pine forest in the vicinity of Nar [ Kuznetsova et al., 2019]. This is a species quite common in coniferous and deciduous communities of the forest belt of Tsey Gorge.

Pseudisotoma sensibilis (Tullberg, 1876) . According to Potapov [2001], P. sensibilis auct . is a complex of closely related species. In the currently accepted broad interpretation, the species occurs almost throughout the Holarctic, including North Ossetia [ Stach, 1947; Kuchiev, 2006]. In the Tsey Gorge, several specimens of this “species” have also been found, but the exact identification requires revision of the entire genus.

Tetracanthella caucasica ( Stach, 1947) . A high-mountainous Caucasian endemic described from the foots of Karaugom and Bezenghi-glaciers [ Stach, 1947] as a subspecies of T. afurcata Handschin, 1919 . It occurs mainly in the central and eastern parts of the North Caucasus, often reaching high abundance levels [ Potapov, 2001]. The species was also recorded from the region of Mount Kazbeg ( Georgia) [ Kováč, 1993] and from the Republic of Dagestan [ Potapov, Kuchiev, 1993]. Regarding North Ossetia, this species is quite common in the highlands, including the nature reserve [ Kuchiev, 1982, 1984, sub T. afurcata ; Potapov, Kuchiev, 1993; Kuchiev, 2006]. In the Tsey Gorge, we have found it only in one of the 12 surveyed plots: the shrub stage of overgrowing of the Tsey foreland (2295 m a.s.l.).

T. osetica Potapov et Kuchiev, 1993 . An endemic Caucasian species described from the North Ossetian Nature Reserve [ Kuchiev, 2006] and still known only from two locations of the republic: Mount Karyukhokh (Skalisty Mountain Range) and Mount Stolovaya (Gerchoch Gorge). According to Kuchiev [2006], another closely related species of the genus, T. arctica Cassagnau , occurs in the nature reserve (Nikolaev peak, 3700 m a.s.l.). The real species identity of this record needs clarification.

Uzelia setifera Absolon, 1901 . The species is distributed throughout Europe, mainly in the mountains.There are records from Crimea and the North Caucasus [ Potapov, 2001], including the nature reserve [ Kuchiev, 2006]. In the Tsey Gorge, we have found only one individual in a maple forest located near the Medik River.

Vertagopus cinereus Nicolet, 1842 . A mostly European species, but many “old” records need to be confirmed due to new descriptions of some related species (in particular, V. pseudocinereus Fjellberg, 1973 and V. haagvari Fjellberg, 1996 ). In the fauna of North Ossetia, V. cinereus was listed by Stach [1947], but its presence in the region has only recently been confirmed [ Lafooraki et al., 2020]. It seems to occur throughout the Caucasus, being a typical inhabitant of spaces under barks and lichens.

** V. haagvari Fjellberg, 1996 . Supposedly a widespread species often occurring together with the previous one. In North Ossetia and in the Caucasus in general, it has not been recorded yet. In the Tsey Gorge , we have revealed it in a pine forest with admixture of birch (2200 m a.s.l.), as well as in a lower beech forest (1865 m a.s.l.).

** Vertagopus sp. Obviously, a new species characterized by weakly developed clavate setae on the tibiotarsi, which brings it similar to species of the genus Desoria . In a recent review of the genus from the Caucasus [ Lafooraki et al., 2020], similar forms have already been observed in the region. These forms seem to be related to high-mountain European species of the genus. In Kuznetsova et al. [2019], this form was listed as Desoria sp. from a pine forest surrounding the village Nar. In our material from the Tsey Gorge, we have found the same form, which turned out to be quite common in forest communities of different ages.