New data about hybridization between Vipera nikolskii and Vipera berus berus

New data about hybridization between Vipera nikolskii and Vipera berus berus New data about hybridization between Vipera nikolskii VEDMEDERYA, GRUBANT & RUDAEVA, 1986 and Vipera berus berus (LINNAEUS, 1758) and their contact zones in Ukraine OLEKSANDR ZINENKO Zusammenfassung Neue Daten über die Hybridisierung zwischen Vipera nikolskii VEDMEDERYA, GRUBANT & RUDAEVA, 1986 und Vipera berus berus (LINNAEUS, 1758) und ihre Kontaktzonen in der Ukraine. Die vorhandenen Daten über Hybridisierung zwischen zwei nah verwandten Otternarten, Vipera nikolskii VEDMEDERYA, GRUBANT & RUDAEVA und Vipera berus (L.) werden dargestellt. Die erste Bastardgeneration der Kreuzung zwischen V. nikolskii und V. berus wurde im Terrarium erzeugt. Morphologisch sind die Hybriden intermediär zwischen elterlichen Arten und Individuen, unterscheiden sich aber von den beiden Arten durch eine größere Anzahl der Ventralia und Subcaudalia. Sechs von neun Hybriden haben Anomalien der Bauchbeschuppung in der Körpermitte. Ein Exemplar hat einen deformierten Kopf und unterscheidet sich von den anderen Hybriden durch seine Körperlänge und Beschuppung. Die Untersuchung der Kontaktzone zwischen den beiden Arten zeigte, dass diese verschiedene Landschaftstypen besiedeln, aber in den Kontaktpopulationen werden Merkmale beider Arten beobachtet. Eine Hypothese über Hybridisierung in den untersuchten Gebieten wurde damit bestätigt. Vergleichende Analyse der Literatur und eigener Daten zeigte auf, dass die Populationen von V. nikolskii und V. berus entlang der Arealgrenze intermediäre Charakteristiken haben. Dies lässt eine weitergehende Hybridisierung zwischen zwei Arten vermuten. Der taxonomische Status von V. nikolskii wird unter Berücksichtigung der Hybridisierungsdaten in der Natur und im Terrarium diskutiert. Schlüsselwörter: innerartliche Hybridisierung; Hybridzonen; morphologische Variabilität; Vipera berus, Vipera nikolskii; Viperidae. Abstract Available data on hybridization of Nikolsky s adder (Vipera nikolskii VEDMEDERYA, GRUBANT & RUDAEVA, 1986) and the common adder (Vipera berus [LINNAEUS, 1758]) are summarised. First generation hybrids between V. nikolskii and V. berus were bred in captivity. Morphologically hybrids are intermediate between parental species and specimens, though they differ from both species in the enlarged number of ventral and subcaudal scales. Six of nine hybrids have ventral scale anomalies in the mid-body area. One specimen has abnormalities of skull bones and pholidosis. The study of adders in contact zones of these species from Central and Eastern Ukraine has shown that these species have a different landscape-specific distribution, but in border populations features of both species appear. An assumption about hybridization in these areas was confirmed. Comparison and analyses of literature and own data shows that specimens of V. nikolskii and V. berus populations alongside the border of their ranges possess intermediate features. This fact allows supposing widespread hybridization of these two species in nature. The taxonomic status of V. nikolskii is being discussed. Key words: Vipera nikolskii, Vipera berus; hybrids; morphology; systematics; Viperidae. 1 Introduction Vipera nikolskii VEDMEDERYA, GRUBANT & RUDAEVA, 1986 is closely related to Vipera berus (LINNAEUS, 1758). Investigators express doubts in the species status of V. nikolskii and consider it as an invalid species or subspecies of V. berus (JOGER et al. Mertensiella 15: 17-28. 2004 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.v. (DGHT) 17

OLEKSANDR ZINENKO 1997, BAKIEV & KRENDELEV 1999, BAKIEV et al. 2000). Differences in hemipenis structure and mitochondrial cytochrome b sequence are very small (JOGER et al. 1997). Nevertheless, the distribution range of this form is well defined and includes almost all the territory of the Silva-steppe zone presumably from Podolian height, Ukraine (TABACHI- SHIN et al., 2003) or even Northern Moldova in the west (TSURKAN, 1989) to the left bank of the Volga, Russia, in the east (VEDMEDERJA et al., 1986). It inhabits mainly broadleaves forests in the East European subboreal humid and semi-humid eminent landscapes as opposed to V. berus, which lives chiefly in mixed or coniferous forests in boreal landscapes (landscapes classification is given by ISACHENKO & SHLJAPNIKOV, 1989). The complex of morphological characteristics is stable in the majority of populations (black colour of all adult specimens, pholidosis). The venom structure has a high level of originality (DAVLJATOV 1973, ORLOV et al. 1990, STARKOV & UTKIN 2001). The cranium demonstrates specific features (KOLDOBA 1983). In spite of the length of the border of the ranges and the comparative availability of both species, to date neither hybridization in captivity, nor investigations of contact zones and of variability in edge populations have been carried out. However, these data are very important in understanding the taxonomic status of V. nikolskii. 2 Material In the experimental hybridization a female V. berus which never mated before, originated from the vicinity of Spartak railroad station (Borodjanka district, Kiev region, Ukraine) was used. Two males of V. nikolskii were taken from the vicinity of Rus ka Lozova village (Dergachi district, Kharkiv region, Ukraine). Both populations are far from the border of the ranges (Kaniv Kursk Tambov Buzuluk after VEDMEDERJA et al. 1986, Fig. 1) and specimens, who have been taken from there, were typical specimens of V. berus and V. nikolskii respectively. Interaction of these species was investigated in the Central and North-Eastern Ukraine: in Kaniv Natural Reserve, Kaniv district, Cherkasy oblast and in Putivl district, Sumy oblast in 2002-2003. In total 28 adders from the vicinity of Kaniv and 15 from vicinity of Putivl were analyzed. Except wild-caught snakes, specimens from collections of the Zoological Museum of Kiev National University (ZMKNU), the Zoological Museum, National Museum of Natural History, Ukrainian Academy of Science (ZMNMNH), the Museum of Nature at V. N. Karazin Kharkiv National University (MNKKNU), and the Zoological Museum of M. V. Lomonosov Moscow State University (ZMLMSU) were investigated. Also for comparison unpublished data kindly given by VALERY VEDMEDERJA and available literature data were used. As pattern of colouration is one of the most distinguishing features of V. nikolskii, two types of colouration of mature snakes were defined: type I totally black or black snakes with whitish supralabials (type of colouration usual in adult V. nikolskii (VEDMEDERJA et al. 1986); type II non-black snakes with or without zig-zag band (type of colouration usual for V. berus and non-mature specimens of both species (VEDMEDERJA et al. 1986, GRUBANT et al. 1973). Data on the frequency of different types of colouration in specimens from the banks of Dnieper in Kaniv vicinity were received from the Annals of Kaniv Natural Reserve from 1970 till 2001 (343 cases of adder observations). In some cases the age of the adders is not known from the Annals. As this information is important, for each bank we have three numbers: 18

New data about hybridization between Vipera nikolskii and Vipera berus berus Fig. 1. Distribution of V. berus and V. nikolskii in the study area. The dashed line illustrates the border of the range of V. nikolskii. Rectangles mark the studied contact zones. Verbreitung von V. berus und V. nikolskii im Untersuchungsgebiet. Die gestrichelte Linie zeigt die Verbreitungsgrenze von V. nikolskii. Rechtecke markieren die untersuchten Kontaktzonen. number of black (type I) adult specimens; number of non-black adult specimens (type II); number of non-black specimens with unknown age, these can be related to both types of colouration. So, ratios of type I and type II in population may be treated with the third class, or without it. Colouration of juvenile specimens of both species is hardly differentiated and was not used. In this work several characters traditionally used in the systematics of Vipera were recorded: number of ventrals (Ventr.), subcaudals (S. cd.), mid-body dorsal scale rows (Sq.), supralabials (Lab.), sublabials (Sub.), circumocular scales (S. or.), rows between eye and supralabials (Or. lab.) (VEDMEDERJA 1989). Also number and locality of anomalous ventral scales were counted (MERILA et al. 1992). 3 Results Description of F1-hybrids In the experiment, the female V. berus gave birth to nine hybrid specimens. The duration of pregnancy was approximately 70 days, which seems to be normal for 19

OLEKSANDR ZINENKO captive conditions (pregnancy duration in V. berus can vary from 45 to 121 days (NAULLEAU 1986)). Morphologically hybrids turned out to be intermediate between parental specimens (Table 1). But the number of ventral and subcaudal scales in hybrids were found to be slightly greater than in parental specimens (Fig. 2). Among hybrid offspring the frequency of ventral scale anomalies in the mid-body area is increased (6 of 9 specimens) (Fig. 3). One male hybrid specimen has hereditary abnormalities: shortened upper jaw, broadened head. Also it has a lower number of ventral scales and is shorter than other specimens (Table 1, Fig. 2). Newborn hybrids are coloured similar to juveniles of both species: brown zig-zag band on light-grey background. There is sexual dimorphism in colouration of hybrids, like as in V. berus (DE SMEDT 2001) and as in juveniles of V. nikolskii (own data). Male specimens have more contrast, fewer and larger dark zig-zag turns and general 20

New data about hybridization between Vipera nikolskii and Vipera berus berus colouration of males is greyish in opposite to brownish colouration of females. Like V. nikolskii (GRUBANT et al. 1973), hybrids become darker after several moults. Male hybrids still keep light elements in colouration (white or light spots on supralabials, mental, canthals, rostral and nasorostral scales, on the edges of ventral and adjacent row of dorsal scales, weakly pronounced zig-zag dorsal band) when they get 450-500 mm in length and become two years old. Female hybrids of the same age and length have a berus-like colouration, which gets darker with time, too. In all specimens the anterior part of the body is brighter than the posterior one (Fig. 4 and 5). Interaction of species and border population morphology The right bank of the Dnieper near Kaniv is known as the limit of the range of V. nikolskii from the description (VEDMEDERJA et al. 1986) (Fig. 1). In the same time, light, berus-like coloured adders have been known from the left bank of the Dnieper near Kaniv (TARASCHUK 1959). Also V. berus inhabits both banks of the Dnieper at a small distance from Kaniv in the Kiev region (own data, collections of ZMNMNH). Suitable habitats alongside the river connect populations and make interaction possible. adders from the population which inhabits deciduous hornbeam-oak forests on the right bank of Dnieper in Kaniv vicinity, are very similar to V. nikolskii. However, several characteristics of external morphology differ from V. nikolskii from Kharkiv region and tend towards V. berus (Table 1, Fig. 2). The majority of the investigated adders are totally black, but with white or lighter coloured supralabials (in both sexes) and light throat (in females) (type I). In spite of the fact that this pattern of colouration Left page: Fig. 2. Variation in number of ventral and subcaudal scales in hybrids and in different populations of V. berus and V. nikolskii. Linke Seite: Variation in Schuppenzahlen (Ventralia und Subcaudalia) bei Hybriden und in verschiedenen Populationen von V. berus und V. nikolskii. Great Britain ($$ n = 21;!! n = 33) (after BOULENGER 1896); NW Russia ($$ n = 29;!! n = 33); Kaniv 1, the left bank of the Dnieper, Ukraine ($$ n = 6;!! n = 2) Kaniv 2, right bank of the Dnieper, Ukraine ($$ n = 11;!! n = 9); Samara, Russia; number of subcaudal scales is unknown ($$ n = 59,!! n = 19) (after BAKIEV et al. 2000); Moscow region, Russia ($$ n = 16,!! n = 24) Nyzhnij Novgorod, Russia (after TABACHISHIN et al. 1996, numbers of specimens are unknown) Tatarstan, Russia ($$ n = 59;!! n = 38) (after PAVLOV 2000); Saratov 1, Russia ($$ n = 2;!! n = 2) (after TABACHISHIN et al. 1996); Saratov 2, Russia ($$ n = 49;!! n = 28) (after TABACHISHIN et al. 1996); Hybrids, V. berus V. nikolskii, F1, ($$ n = 4;!! n = 4); Hybrids, V. berus V. nikolskii, F1, specimen with reduced number of ventral scales; Belgorod, Russia ($$ n = 11;!! n = 21); Kharkiv 1, Ukraine ($$ n = 30;!! n = 28); Kharkiv 2, Ukraine ($$ n = 19;!! n = 18). 21

OLEKSANDR ZINENKO V. berus from Adders from the Parental Female hybrid Male hybrid Anomalous Parental Parental Adders from the V. nikolskii from Pskov and left bank of the specimen, specimens specimens hybrid specimen, specimen, right bank of the Kharkiv vicinities Novgorod regions, Dnieper near! V. berus n=4 n=4 specimen, $ No. 1 $ No. 2 Dnieper near (MNKKNU N-W Russia Kaniv male. V. nikolskii V. nilkolskii Kaniv collection) (MNKKNU and ZMLMSU collections) L., mm 560,00 170,25±2,95 156,00±2,04 140,00 507,00 502,00 L. cd., mm 77,00 22,25±1,03 28,50±0,96 24,00 82,00 96,00 Ventr. $$ - 144,67±0,55 $$ - 147,75±1,62 147,00 155,25±1,38 151,50±1,19 135,00 151,00 151,00 $$ - 149,36±1,00 $$ - 149,78±0,53 (140-149), n=18 (142-153), n=6 (144-155), n=11 (146-155), n=23!! - 148,75±0,35!! - 147, 149!! - 153,78±0,84!! - 153,87±0,65 (146-151), n=16 (150-158), n=9 (148-159), n=23 Sq. 20,34±0,15 (19-21) 21,13±0,48 21,00 21,75±0,48 21,25±0,25 21,00 21,00 23,00 21,15±0,11 21,42±0,12 (19-23), n=8 (21-23), n=20 (21-23), n=46 S. cd. $$ - 41,12±0,28 $$ - 40,67±0,21 31,00 33,75±1,44 44,00±0,71 41,00 41,00 44,00 $$ - 40,55±0,88 $$ - 40,42±0,57 (39-43), n=18 (40-41), n=6 (35-45), n=11 (36-46), n=21!! - 32,0±0,43!! - 31,33!! - 32,63±0,75!! - 34,05±0,48 (30-35), n=16 (30-35), n=8 (30-38), n=21 Lab. 8,69±0,07 (8-10), 8,63±0,16 9,00 8,75±0,25 9,00 9,00 9,00 9,00 8,98±0,06 8,97±0,05 n=34 (8-9), n=8 (8-10), n=20 (8-10), n=46 S. or. 8,79±0,13 (7-10), 8,94±0,27 8,00 7,75±0,25 8,25±0,48 8,00 9,00 9,00 9,25±0,18 9,49±0,14 n=34 (8-10), n=8 (8-11), n=20 (7-11), n=45 Or. lab. $$ - 1, n=18 $$ - 1, n=6 1,5/1,5 1 1 1 1/1 1,5/1 $$ - 1, n=11 $$ - 1,15±0,06!! - 1,04±0,02!! - 1/1,5; 1/1!! - 1,39+-0,13 (1-2), n=23 (1-1,5), n=16 (1-2), n=9!! - 1,26±0,06 (1-2), n=22 Tab. 1. Morphology of hybrids, parental specimens and specimens of adders from the vicinity of Kaniv in comparison with V. berus and V. nikolskii populations. Morphologie von Hybriden, Elternarten und Exemplaren von Vipern aus der Region Kaniv im Vergleich mit Populationen von V. berus und V. nikolskii. 22

New data about hybridization between Vipera nikolskii and Vipera berus berus Fig. 3. Frequency of ventral scales anomalies in the hybrid brood and different populations of V. berus and V. nikolskii. Häufigkeit von Ventralschuppen-Anomalien im Hybridwurf und in verschiedenen Populationen von V. berus und V. nikolskii. Sweden, V. berus, n = 229 (after MERILÄ et al. 1991); NW Russia, V. berus, n = 20; Moskow, V. berus, Russia, n = 24; Voronezh, V. nikolskii, Russia, n = 14; Kharkiv, V. nikolskii, Ukraine, n = 59; Hybrids, V. berus V. nikolskii, F1, n = 9; Kaniv 1, left bank of the Dnieper, Ukraine, n = 8; Kaniv 2, right bank of the Dnieper, Ukraine, n = 9. was included in the description of V. nikolskii (VEDMEDERJA et al. 1986), specimens with light supralabials and throat are very rare in most populations of V. nikolskii. Nonblack, berus-like coloured adult specimens (type II) (Fig. 7) were observed here with a frequency of 5,9-11,2 %. The morphology of specimens from the left bank territories of Kaniv Nature Reserve is more similar to V. berus, but considerably tends towards V. nikolskii (Table 2, Fig. 2). Adult specimens with a colouration of type II were observed with a frequency of 33,3-45,5 %, whereas the proportion of nikolskii-like coloured specimens in the population can be estimated as 54,5-77,7 % (n = 45-55). adders inhabit newly formed islands in the Dnieper between the two previously mentioned populations. Unfortunately, we have no specimens from islands, but after Annals of Kaniv Natural Reserve the ratio of different types of colouration here appears strongly displaced towards the berus-type (80,0-94,2 %, n = 10-35). The frequency of mid-body anomalies of ventral scales is low in left- and is comparatively high in right-bank populations (Fig. 3). Maximum number of anomalies of ventral scales per specimen is 25. This is surprising, because of the compara- 23

OLEKSANDR ZINENKO Fig. 4. Male hybrid specimen at an age of 3 months. Männlicher Bastard im Alter von 3 Monaten. Fig. 5. Female hybrid specimen at an age of 3 months. Weiblicher Bastard im Alter von 3 Monaten. tively small number of investigated snakes it is an extremely high quantity. For comparison the maximum number of anomalous scales for 229 specimens from Sweden is seven (MERILA et al. 1992). Also we observed one adult female specimen from the right bank population, which has unusual morphological features. It has dark colouration, a weakly pronounced zig-zag band, unusual body proportions too short tail, only 26 subcaudal scales, comparatively thin body and high, but short and small head, big eyes, highly oligomerized pileus (Fig. 6). This specimen differs strongly from any other specimens in this population and seems to be anomalous. In the vicinity of Kaniv V. berus and V. nikolskii occupy different landscapes and biotopes (LOPAREV & SYTNIK 2003, own data). V. nikolskii populates deciduous hornbeam-oak forests on heights of the right bank of the Dnieper at an absolute altitude 24

New data about hybridization between Vipera nikolskii and Vipera berus berus Fig. 6. Adult female specimen with zig-zag band from a V. nikolskii population on the right bank of Dnieper near Kaniv. Adultes Weibchen mit Zickzackband aus einer V. nikolskii-population auf dem rechten Ufer des Dnieper bei Kaniv. Fig. 7. Very rare berus-like coloured male adult specimen from V. nikolskii population on the right bank of Dnieper near Kaniv. Sehr seltenes berusartig gefärbtes adultes Männchen aus einer V. nikolskii-population auf dem rechten Ufer des Dnieper bei Kaniv. of about 200 m. The common adder lives here in intra zonal mixed forests on the edge of river-plane and on the alluvial terraces along left bank of the Dnieper at an altitude about 130 m. 25

OLEKSANDR ZINENKO Another case of contact between these species is known in the north of the Sumy oblast, North-Eastern Ukraine (fig 1). In contrast to the Kaniv area, a transition from V. berus to V. nikolskii was found along the same, right bank of the Seym river in Putivl district of Sumy oblast. Populations of V. berus and V. nikolskii were found in 30 km one from another. A shared feature with the Kaniv populations is the association of different species with different landscapes. V. nikolskii inhabits deciduous forests on the edge of the Middle Russian Heights at the absolute altitude of about 200 m in the vicinity of Nova Sloboda village. V. berus lives in mixed deciduous-coniferous forests on lowland plain with an absolute altitude of about 130 m in the vicinity of Spadschina village. The small number of studied snakes in this region is not sufficient for a complete analysis of the situation here but the same tendencies as in the first place are obvious. Like in Kaniv, populations of both species have features of introgression. In case of V. nikolskii these are changed pholidosis characters (Fig. 2) and light elements in colouration. In the V. berus population black specimens are frequent and morphology has common features with V. nikolskii. From 17 specimens of both species from this region one specimen has nine ventral scale anomalies. The analysis of literature and own data on variability of adders from other regions, where sympatric or parapatric occurence of V. nikolskii and V. berus may be supposed, shows that almost all of such populations possess intermediate features. Light elements in colouration are observed in populations of V. nikolskii from Tambov (SOKOLOV 1979), berus-like coloured specimens in V. nikolskii populations are known from the north of Saratov region and Tatarstan (TABACHISHIN et al. 1996, PAVLOV 2000), black adders with morphological characteristics of V. berus inhabit vicinity of Samara (BAKIEV et al. 2000). Similarly, populations of V. berus from Nyzhnij Novgorod (TABACHISHIN et al. 1996) and Moscow region differ from V. berus populations in the North-Western Russia and Western Europe and have enlarged numbers of ventral and subcaudal scales (Fig. 2). These facts allow to suppose widespread hybridization and introgression among these two species. Intermediate populations are known mainly alongside big rivers (Dnieper and Volga), which are connecting their natural habitats. But some conclusions arise because V. nikolskii-like adders occur in mixed forests on Kama and Volga banks in Tatarstan Republik (PAVLOV 2000). These data considerably enlarge the distribution range of V. nikolskii and leaves the question about the existence of isolation mechanisms in nature still unsolved. 4 Conclusions Thus, V. berus and V. nikolskii can hybridize and give viable F1 hybrids. In addition to own data, F1-hybrids between V. berus from the vicinity of Tula and V. nikolskii from Voronezh region, the Khopior river basin were obtained in Tula exotarium (SHIRYAEV KONSTANTIN pers. comm.). Indication of fertility of F2-hybrids between V. nikolskii from Kaniv and Kharkiv and V. berus from Russia, Byelorussia and Ukraine was published without any data about conditions of experiment and description of hybrids (KURILENKO 2003). Numerous populations with intermediate morphology may testify that V. berus and V. nikolskii hybridise easily both in nature and have a wide zone of introgression. Certainly, all these facts can be arguments for subspecies level of V. nikolskii. However free hybridization alone is insufficient to make a final decision about the status of V. nikolskii. Hybrids are also known between good species in the genus Vipera (for example Vipera seoanei Vipera aspis zinnikeri or in a complex of Caucasian vipers, 26

New data about hybridization between Vipera nikolskii and Vipera berus berus SAINT GIRONS 1977, ORLOV & TUNIYEV 1986). On the other hand, increasing of mid-body ventral scales anomalies and malformations in hybrid brood and in nature population from the contact zone may indicate that some barriers for free hybridization exist. An important fact in understanding the interaction of these species is the separate distribution in different landscapes and comparatively small distance of transition from one species to another. However, V. berus and V. nikolskii in other regions can inhabit both types of these landscapes. Thus landscape differentiation probably is not only a result of differentiation in ecology or species competition, but chiefly is effected by different origin of species and the colonization history of this territory. We suggest that Vipera nikolskii has appeared after the range disjunction during one of the ice ages in refuges on heights in eastern Europe. After climate changed recently V. berus recolonized boreal landscapes and in absence of strict geographical and reproductive isolation started to hybridize with V. nikolskii. The last word in the dispute about the status of V. nikolskii could be based upon results of investigations of the most isolated populations from the southern part of the species range. Distribution of both species, their hybrid zone, possible ecological divergence in these areas, are to be investigated, too. Acknowledgements The author would like to express gratitude to all people who have helped them in obtaining data for this paper, namely CHORNIY M., KIRILENKO I., MALYJ A., NARSEEVA L., ORLOVA V., PISANETS E., ROZORA ZH., local people in Sumy oblast and especially to RUZHELENKO N. Also the author would like to thank ZINENKO E. for support and patience, KOTENKO T. for general guidance and help, SHABANOV D., STRELKOV D., RUDIK A. PERETS A. and especially VEDMEDERJA V. for advice and critique. References BAKIEV, A.G. & V.V. KRENDELEV (1999): Comparison of topography of internal organs of common adder and Nikolsky s adder. Actual problems of herpetology and toxinology, 3: 60-62 (in Russian)., MALENEV, A.L., A.N. PESKOV & D.V. GRIDNEV (2000): Morphological characteristics of adders from the forest-park zone of Samara. Actual problems of herpetology and toxinology, 4: 3-8 (in Russian). BOULENGER G.A. (1896): Catalogue of the Snakes in the British museum., Vol. 3. London: 476-481. DAVLJATOV, J.D. (1973): Some results of an investigation on snake venoms variability. Questions of herpetology, Proceedings of the III herpetological conference, Leningrad: 65 (in Russian). GRUBANT, V.N., A.V. RUDAEVA & V.I. VEDMEDERJA (1973): On the systematic status of the black morph of the common adder. Questions of herpetology, Proceedings of the III herpetological conference, Leningrad: 68-71 (in Russian). ISACHENKO, A.G. & A.A. SHLJAPNIKOV (1989): Nature of the world. Landscapes. Moskow, Mysl : 504. JOGER, U., P. LENK, I. BARAN, W. BÖHME, T. ZIEGLER, P. HEIDRICH & M. WINK (1997): The phylogenetic position of Vipera barani and of V. nikolskii within the Vipera berus complex. Herpetologia Bonnensis: 185-194. KOLDOBA, I.V. (1983): Comparative eco-morphological analysis of skull structure of some Vipera species from USSR (Vipera berus berus, Vipera kaznakovi, Vipera ursinii renardi). The degree project. Kharkiv National University: 107 (in Russian). KURILENKO, V.E. (2003): About reliability of presence of Vipera nikolskii in the Kaniv Nature Reserve. Nature reserves in Ukraine 4, 1: 55-56 27

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