Forgotten for two centuries: redescription of Phoxinus isetensis (Georgi, 1775) (Cypriniformes, Leuciscidae) – the most widespread minnow in Europe

The morphology, phylogenetic position, and distribution of a recently revalidated species of leuciscid minnow, Phoxinus isetensis , were substantially clarified. The species was described in the late 18 th century from the Middle Urals but later synonymized with Phoxinus phoxinus . As believed, P. isetensis is distributed in the Arctic Ocean catchment from the Murman coast via West and East Siberia until the Pacific Ocean catchment in Far East and Northeastern Asia. Our study, with the use of mtDNA markers coupled with extensive morphological data, showed that the distribution of P. isetensis is greatly different. Currently, this is the most wide - spread Phoxinus species in Europe, distributed in Northern and Eastern Europe and on the western edge of Siberia (Iset and Ural basins). In particular, P. isetensis inhabits the basins of the Caspian, Baltic, White, Barents, and Kara seas, possibly occurring in the North Sea basin. The species was redescribed, and the type locality and neotype were designated. The main morphological differ - ence from other Phoxinus spp. is the large total number of vertebrae (39–43, mode 41) due to an increase in the number of caudal vertebrae (16–21, mode 19). Phylogenetically, P. isetensis is a sister to the Caucasian species P. colchicus ( p -distance = 5%). The wide distribution of P. isetensis within the area of the Last Glacial Maximum suggests rapid colonization of deglaciated regions, probably due to its adaptation to a cold climate.


Introduction
Minnows of the genus Phoxinus Rafinesque, 1820, are predominantly rheophilic small freshwater fish of the family Leuciscidae Bonaparte, 1835, widespread in northern Eurasia from the Pyrenees to the Pacific coast.
Along with the productive revision of the taxonomic and genetic diversity of species distributed in Western and Central Europe, the remaining part of the range, including Eastern Europe, was almost unexplored.For instance, taxonomic identification of northern and eastern European minnows with the largest range in Europe was problematic; those were assigned to mitochondrial Clade 17 without species naming (Palandačić at al. 2017(Palandačić at al. , 2020)).Our genetic data showed that unnamed Phoxinus sp.Clade 17 is conspecific to recently revalidated Phoxinus isetensis (Georgi, 1775) (Dyldin et al. 2023) described from the Middle Urals.This study aimed to make taxonomic redescription using the integrative (morphology and genetics) approach, to outline geographic distribution, and to clarify the phylogeny of P. isetensis.

Sampling
Materials for morphological studies and partially for genetic studies were collected by the authors.Fish were caught using a frame net and seine net with a mesh size of 6-8 mm.Fish were euthanized in a solution of clove oil and photographed in an aquarium with artificial lighting using a Nikon D5300 camera (Nikon Corporation, Tokyo, Japan) with a Nikkor 60 mm f/2.8G lens (Nikon Corporation, Tokyo, Japan) using a physical white swatch for color correction.Fin clips (pectoral or pelvic) were taken from some specimens (DNA vouchers) and placed in 96% ethanol for subsequent DNA extraction in the laboratory.Then most fish were preserved in 10% formalin (form.), while some samples (usually small-sized specimens) were preserved in 96% ethanol for molecular analysis.Subsequently, formalin-fixed specimens were washed out in running water and transferred to 70% ethanol for long-term storage.
Neotype and additional material were deposited at the Fish Collection of the Papanin Institute for Biology of Inland Waters of the Russian Academy of Sciences, Borok, Russia (IBIW_FS).

Morphological studies
Morphological material on Phoxinus sp.(Clade 17) from seventeen localities (n=272, Fig. 1, Suppl.material 1) was examined.In studying the morphology of Phoxinus, we follow Bogutskaya et al. (2019Bogutskaya et al. ( , 2023) ) and Artaev et al. (2024).In particular, 42 morphometric (Suppl.materials 2, 3), 17 meristic, and two qualitative characters (Suppl.materials 2, 4) were processed.Abbreviations of morphometric characters are seen in Suppl.material 3. Morphometric measurements were taken from the left side of the body using a digital caliper to the nearest 0.1 mm by one operator for the purposes of consistency as recommended by Mina et al. (2005).Meristics (except for axial skeleton) and type of breast scalation (Bogutskaya et al. 2019) were assessed using material stained in an ethanol solution of alizarin red S (Taylor and Van Dyke 1985 with modifications), followed by short exposure to 1-2% potassium hydroxide and preservation in 70% ethanol.
Sex was determined by the shape and size of the pectoral fins, their rays, and the length of the pelvic fins (Frost 1943;Berg 1949;Chen 1996;Bogutskaya et al. 2019).External meristics were counted on the left side.Standard length (SL) was measured from the tip of the upper lip to the end of the hypural complex.The total number of pectoral and pelvic-fin rays was counted on the left fins.The last two branched rays articulated on a single pterygiophore in the dorsal and anal fins are counted as one.Scales above the lateral line were counted between the lateral line and base of the first unbranched ray in the dorsal fin; scales below the lateral line were between the lateral line and base of the first unbranched ray in the anal fin.In both cases, lateral line scales were not taken into account.The number of anterior gill rakers of the first gill arch was counted on the left and right sides of the specimens.Number lines on the scales were counted on the left and right breast patches, and an average value was taken.The counts of meristic characters (except for the axial skeleton) and assessment of qualitative characters were done using the stereomicroscope MC-2-ZOOM (Micromed, Saint Petersburg, Russia).Vertebrae and pterygiophores were counted following Naseka (1996) and Bogutskaya et al. (2019) using radiographs made by X-ray equipment PRDU II (ELTECH-Med, Saint Petersburg, Russia).Images of pharyngeal teeth were obtained using a JEOL JSM-6510LV scanning electron microscope (Jeol, Tokyo, Japan).
Measurement indexes were statistically processed in Microsoft Excel.Comparison of multiple samples was carried out using the Kruskal-Wallis test followed by Dunn's post hoc test with Bonferroni correction [rstatix (Kassambara 2020) and tidyverse (Wickham et al. 2019) packages in R version 4.3.1 (Ihaka and Gentleman 1996)].Principal component analysis (PCA) was performed using the ggfortify (Tang et al. 2016) package in R. Differences between sexes were tested using the Mann-Whitney U test in Past 4.13 (Hammer and Harper 2001).
Phylogenetic placement and genetic distance.
The average intra-group as well as the average pairwise intergroup p-distances using the concatenated COI+cytb sequences data set were calculated using the MEGA7 program (Kumar et al. 2016) with 1000 bootstrap replicas.

Phylogenetic placement and genetic distance
The phylogenetic Bayesian tree of the genus Phoxinus shows that P. isetensis has its own lineage, being sister to P. colchicus distributed in the eastern Black Sea basin and the Kuban system in the Sea of Azov basin (p-distance = 0.050±0.005)with a high support in both BI (Fig. 2) and ML (Suppl.material 7) analyses.Three species combined together (P.isetensis, P. colchicus, and P. chrysoprasius) are early branching in the Phoxinus tree and represent a sister class to all other European Phoxinus spp.apart from P. adagumicus, although this was weakly supported.Intraspecies divergence of P. isetensis is moderate (0.005) despite its wide distributional range (Suppl.material 8)."Галïанъ" or "солдатъ" (without Latin species name) -Lepechin 1772: 309 (upstreams of the Isset, Chusovaya, and Tura rivers).
Etymology.Since Lepechin (1771: 491) described species from the vicinity of Yekaterinburg, it can be assumed that Georgi (1775: 621) (see taxonomic remarks) gave its name to the Iset River, flowing through Yekaterinburg.
Description.The live and preserved appearance as well as radiograph of neotype is shown on Fig. 3, general appearance of live specimens of Phoxinus isetensis from different basins is shown on Fig. 4, morphometrics of neotype and additional material from the type locality with level of significance of sex-related differences are given in Table 1, meristic and qualitative characters for specimens from the type locality are given in Table 2, and primary morphological data for specimens from the type locality (neotype and additional material) are given in Suppl.material 2, the meristic and qualitative characters of P. isetensis and Phoxinus spp.are given in Suppl.material 4, the morphometrics of P. isetensis, P. adagumicus, P. chrysoprasius, and P. colchicus and their comparison are given in Suppl.material 3.    1, Suppl.material 3).The maximum size among studied specimens 76.3 mm SL.The species has a slender and elongated caudal peduncle.The caudal peduncle depth 6.9% SL in neotype, 6.9-8.8%SL in additional material from type locality, and 6.6-9.5% SL in other additional materials (here and further -from basins of Caspian, Baltic, Barents, and Kara seas); caudal peduncle depth 28.7% in caudal peduncle length in neotype, 28.7-36.5 in additional material from type locality, and 26.9-40.6 in other additional material; caudal peduncle depth 3.5 times the caudal peduncle length in neotype, 2.9-3.4 in additional material from type locality, and 2.5-3.7 in other additional material.The species has a slender body, body depth at dorsal-fin origin 18.0% SL in neotype, 15.9-20.0 in additional material from type locality, and 14.7-21.6 in other additional material.Eyes larger (horizontal eye diameter: 26.2% HL in neotype, 25.3-29.6 in additional materials from type locality, 23.4-33.8 in other additional).
Forty-two total vertebrae in neotype, 40-42 in additional material from type locality, and 39-43 in other additional material from basins of Baltic and Barents seas, Volga and Ob rivers, commonly 41 vertebrae.Twenty-one abdominal vertebrae in neotype, 21-23 in additional material from type locality, and 21-24 in other additional material from basins of Baltic and Barents seas, Volga and Ob rivers, commonly 21-23 vertebrae.Twenty-one caudal vertebrae in neotype, 17-21 in additional material from type locality, and 16-21 in other additional material from basins of Baltic and Barents seas, Volga and Ob rivers, commonly 18-20 vertebrae.Fourteen predorsal vertebrae in neotype, 14-16 in additional material from type locality, and 13-16 for other additional material from basins of Baltic and Barents seas, Volga and Ob rivers, commonly 14-15 vertebrae.Three anal-fin pterygiophores in front of the first caudal vertebrae in neotype, 3-6 in additional material from type locality, and 3-7 in other additional material from basins of Baltic and Barents seas, Volga and Ob rivers, commonly 4-6 pterygiophores.Difference between numbers of abdominal and caudal vertebrae zero in neotype, zero to 6 in additional material from type locality, and zero to 7 for other additional material from basins of Baltic and Barents seas, Volga and Ob rivers, commonly 2-5.
Seven to 10 (mode 8) gill rakers (in series from type locality) on first arch.
Qualitative characters.Pectoral fins do not reach the beginning of pelvic fins in females and most of the males (ca.75%).In the most specimens (ca.85%) tip of the upper lip above horizontal level of lowest point of the eye and in about 5% of specimens -at this level.Origin of anal fin is mainly ahead or at vertical level of posterior insertion of the dorsal fin (ca.45% for each form), rarely behind (ca.8%).Free margin of the dorsal fin is mainly straight or slightly convex, rarely slightly concave; anal fin most often slightly concave and straight, rarely slightly convex.3 rd -6 th type of breast scalation (mode 4 th type, often 3 th type, 5 th and 6 th type are less common) (Fig. 5B, Suppl.material 4).
Coloration.Males and females outside of spawning have predominantly brown coloring of the upper half of the body and light lower part in males and white in females (Fig. 4).Juveniles often show a large contrast: the black horizontal stripe and the white belly.During spawning, color of both sexes becomes much brighter, the color of the sides is dominated by green (many males become dark green, almost black), in front, it is mixed with golden, less often purple and red.In males, as well as some females, the lips and lower jaw, as well as body at the bases of the pectoral, pelvic, and anal fins, become red.The operculum is blue and the suboperculum is yellow in both sexes, but coloration is much more pronounced in males.In both sexes, the bases of ventral and anal fins are light blue.The specimens preserved in formalin had a yellowish color, which is somewhat darker with a brown tint in the upper parts.
Sexual dimorphism.Significant differences are observed in 18 out of 41 morphometric characters (Table 1).In general, females have smaller relative anal (analfin depth), dorsal (dorsal-fin depth), pelvic (pelvic-fin length), and pectoral fins (pectoral-fin length), a greater predorsal length, and pectoral -pelvic-fin origin length.In females, the pectoral fins never reach the pelvic fins, while in ca.25% of males, reach.
Taxonomic remarks.According to the early literary sources reviewed in Berg (1912), the first name within the range of species is Cyprinus isetensis, given by Georgi (1775: 621), which lists species (without description) for the Chusovaya River with reference to Lepechin (1771: 491).Lepechin gives a description of the species but does not give the species name, designated as "CYPRINVS" with the type locality "circa Catharinopolin" (now Yekaterinburg).Although Georgi does not provide a description of species when mentioning the name isetensis, he makes a reference to the description of this species in Lepechin's study, which makes this name valid since it complies with Art.12.1 and 12.2 of the International Code of Zoological Nomenclature (ICZN 1999).
Type locality.The type locality from the original description (Lepechin 1771: 493) is "… habitat in rivis scopulosus circa Catharinopolin," which means "… lives in the rocky streams around Catharinopolin (now Yekaterinburg)."Probably Lepechin meant the upper reaches of the Iset, Chusovaya, and Tura rivers, which were specified in further publication (Lepechin 1772: 311).
Type locality for the neotype: Severka River (56.8830°N, 60.2716°E) upstream of Severka village near Yekaterinburg, Sverdlovsk Oblast, Russia (Fig. 6).A tributary of the Reshotka River → Iset River → Tobol River → Irtysh River → Ob River → Kara Sea.Nomenclatural and taxonomic actions.The need to designate a neotype for P. isetensis is determined by the following considerations: first, our attempts to find a type specimen at the Zoological Institute of the Russian Academy of Sciences, Saint Petersburg, Russia (ZISP), where the largest and oldest ichthyological collection in Russia is stored, were unsuccessful.At the end of the 18 th centu-ry, at the time of the description of P. isetensis, it was the only scientific organization in Russia where type specimens were deposited.The type specimens of P. isetensis were absent in the ZISP already at the beginning of the 20 th century (Berg 1912).Second, no type specimens for all the fish species described by the naturalist and explorer Johann Gottlieb Georgi (1729-1802) were designated   (Fricke et al. 2024).Thus, we conclude that Georgi did not designate a type series for this species.Third, in addition to P. isetensis, at least one more species of this genus inhabits the Ob River basin-P.ujmonensis Kashchenko, 1899 (see Discussion), and their possible sympatric co-occurrence requires further clarification.
Thus, based on the above-mentioned circumstances and in accordance with Article 75 of the ICZN, we designate a neotype for P. isetensis.Our nomenclatural actions do not contradict the statements of Article 75.3 (qualifying conditions), and the designation of a nomenclatural type (neotype) for P. isetensis, as a widespread species living in Europe and Asia, will make it possible to clearly describe both morphological and genetic differences from other species of the genus Phoxinus (Articles 75.3.1 and 75.3.2).
Distribution and habitat.Widespread in northern and eastern Europe and in the western edge of Siberia (Iset and partially Ural basin).Phoxinus isetensis inhabits the basins of the Caspian, Baltic, White, Barents, and Kara seas, possibly occurring in the North Sea basin.In the Caspian Sea basin, it is widely distributed in the upper and middle Volga, Kama, in the mountainous part of the Ural basin.In the Baltic Sea basin, it is widespread in the northern and eastern parts.In the Kara Sea basin, it is known in the Iset basin (Ob basin).According to Palandačić et al. (2017Palandačić et al. ( , 2020)), mtDNA of this species (Clade 17) was detected in Scandinavia and the British Isles, suggesting that minnows from these areas also belong to the species P. isetensis.Dyldin et al. (2023: 671) pointed out the distributional range of P. isetensis as "Arctic Ocean basin, from Murman coast to East Siberian Sea basin (Kolyma basin); rivers of northern and western Sea of Okhotsk basin (Ola and Uda rivers); rivers of Peter the Great Bay drainage, probably Amur River basin, and northwestern Sakhalin Island."This data only partially corresponds to the above-mentioned range.See further explanations in the discussion.
Morphology comparison.PCA of 41 morphometric characters shows differences between P. isetensis and P. adagumicus, P. chrysoprasius, and P. colchicus from the Crimean Peninsula and the Caucasus (Fig. 7).The greatest difference is from P. colchicus (no overlap), while the remarkable overlap with the other two species (P.adagumicus and P. chrysoprasius) is noted.

Discussion
Our study recognized the unnamed Phoxinus sp. with the largest range in Europe (Clade 17 sensu Palandačić et al. 2017) as P. isetensis, the species that was described from the upper reach of the Chusovaya River (Kama-Volga basin) and the Iset River basin (Ob basin) in the Middle Urals.We redescribed the morphology and significantly clarified the distributional range of this species.According to our results, P. isetensis can be distinguished from other neighbor species by the large total number of vertebrae -39-43 (mode 41) (vs. 37-42), primarily due to an increase in the number of caudal vertebrae -16-21 (mode 19) (frequency distribution see in Suppl.material 4) and in sequences of COI mtDNA (minimal p-distance = 0.05 to closely related P. colchicus).Remarkably, there is some discrepancy between the genetic and morphological similarities of P. isetensis.Being close genetically to P. colchicus from the West Caucasus, it has more significant morphological differences with this species compared to other phylogenetically more distant species, P. adagumicus and P. chrysoprasius (Figs 2, 7).In particular, these species are more similar to P. isetensis in total number of vertebrae and number of caudal vertebrae (Suppl.material 4).Of the eighteen populations of P. isetensis, seventeen had modes of 41 or 42 vertebrae, and only one population from the Baltic Sea basin had 40 vertebrae.This main morphological difference -an increased number of vertebrae and northernmost range relative to other European Phoxinus -is consistent with Jordan's rule (vertebral number in fish increases with latitude) (McDowall 2008).However, it is noteworthy that within the species range extended in the latitudinal direction for more than 2000 km within 51-69 northern latitudes, there was no correlation.
Phoxinus isetensis redescribed in this study was recently revalidated in Dyldin et al. (2023), but the authors outlined its range mistakenly for the whole of West and East Siberia as well as for Northeast Asia and the Far East due to the absence of genetic and morphological data.According to our genetic results, the P. isetensis described from the rivers near Yekaterinburg belonging to both the upper stream of left tributaries of the Ob River and the Chusovaya River itself (Kama-Volga basin) are identical or very similar (conspecific) to other samples from the Volga basin, the Ural basin, and the remaining range as outlined for Clade 17 sensu Palandačić et al. (2017).Therefore, P. isetensis has a huge range in northern and eastern Europe, extending approximately 3.800 km from west to east and 2.000 km from north to south.Its range in Europe includes the basins of the Caspian, Baltic, White, Barents, and North Seas.In the Caspian Sea basin, it is widespread in the Upper and Middle Volga and Kama basins.In the Baltic Sea basin, it is widespread in the northern and eastern parts.In the North Sea basin, it is noted for Scandinavia and the British Isles (Palandačić et al. 2017).
To the best of our knowledge, the occurrence of P. isetensis in Asia is restricted to the Ural basin (Caspian Sea basin) and the Iset basin (Tobol River → Irtysh River → Ob River, which flows into the Kara Sea).The Ural Mountains are a well-known biogeographic barrier between Europe and Asia (Abell et al. 2008), which, however, is characterized by the corridor linking Europe and Asia in the Middle Ural via the Chusovaya River Valley.It was assumed this corridor might facilitate aquatic fauna exchange between Siberia (Ob basin) and European Russia (Volga basin) (Kostarev 1973;Makhrov et al. 2021).The Chusovaya River belongs to the Kama-Volga basin, but its upper reaches are located in Siberia -eastward the main Ural ridge and sharing a watershed with the Ob basin through the Iset river basin.We have to note that in the upper reaches of the Chusovaya River, there are a number of man-made reservoirs.One of those, the Volchikha Reservoir, has a connection through a small artificial canal to the Ob basin via the Reshotka River, a tributary of the Iset River.The reservoir and canal are dated to the mid-1940s (Korlyakov and Nohrin 2014).Although it can be assumed that an artificial canal could facilitate the dispersal of P. isetensis from the Kama-Volga system to the Ob basin, populations of minnow, at least in the Iset basin, apparently colonized the Ob basin rather earlier.First, it is supported by early evidence of the presence of conspecific populations in both the Ob and Chusovaya basins by Lepechin (1772) andGeorgi (1775).This is further supported by the fact that not only the Severka (type locality), but other rivers in the Iset basin, inhabited just one species of minnow, P. isetensis -for instance, in the Kushtumga River (genetic data), which is located ca. 750 km along the riverbed from the canal connecting the Volga and Ob basins near Yekaterinburg (Fig. 1).
Our finding in the distributional pattern of P. isetensis is additional evidence of faunal exchange between Siberia and Europe via the Chusovaya River Valley.Contrary to previous observations and suggestions on fish migrations from Siberia to Europe (Kostarev 1973;Marić et al. 2014;Perdices et al. 2015;Levin et al. 2017;Zinoviev and Bogdanov 2017;Vinarski et al. 2021), the case of P. isetensis suggests that fish migrations took place in the reverse direction too.Remarkably, the eastward direction of the recent (seemingly postglacial) colonization pattern of P. isetensis is also corroborated by its presence in the Upper and Middle Ural systems.
Noteworthy, one more Phoxinus species inhabits the Ob basin -P.ujmonensis, described from the upper tributaries of the Ob in the Altai Mountains.This species is genetically distant from P. isetensis (Fig. 2, Suppl.material 7).Our unpublished molecular data indicate that the distribution of P. ujmonensis in the Ob basin is not restricted by the Altai Mountains.The distribution of both species in the Ob basin needs further clarification.
Based on the current distribution of P. isetensis (Fig. 1), this species might rapidly colonize large northern areas following the deglaciation of the last Pleistocene glaciers.This is in line with the previously proposed hypothesis about the colonization of Scandinavia by freshwater fish from the southeast (Museth et al. 2007).Within the boundaries of the Last Glacial Maximum (LGM), the habitation of two other Phoxinus species (clades) is confirmed -P.cf.morella and Clade 10 (P.phoxinus) from Ireland, with an unknown origin of population that might be introduced -Denys et al. (2020) (Fig. 1).However, northern populations of those species are located on the southern periphery of the LGM, while P. isetensis inhabits most of the deglaciated region.One may suggest that during the colonization of new habitats after LGM, P. isetensis could hybridize with other minnow species.This hypothesis may be supported by a decrease in the total number of vertebrae (mean 40.5 vs. 41.1 in the rest of the range, Suppl.material 4) in the potential contact zonethe east of the Baltic Sea basin-and it should be tested in the future.It is noteworthy that in northern Norway, the Phoxinus minnow has been a significant expansion of the range as a result of introductions since the 1900s (Museth et al. 2007); its ancient DNA was not found in the sediments dating to 5.6-13 thousand years ago from the Storsteinhola cave, while the ancient DNA of species currently sharing biotopes with Phoxinus (Barbatula sp. and Gobio gobio) was found (Boilard et al. 2024).Seemingly, along with the post-glacial expansion of P. isetensis northward, a shrinking of the range from the south can be suggested.For example, Falk (1786: 432) recorded Cyprinus phoxinus for the Volga and small rivers ("Zariza, Jelschanka.Sarpa u. f.") near Volgograd city in Russia (Fig. 1).This is > 450 km southward from the most southern contemporary records in the upper reaches of the Tereshka (Artemyeva and Selishchev 2005) and Sura basins within the Volga system.Although the right drainage of the Volga north of Volgograd is steep and rich in small tributaries with fast-flowing water, minnows were not recorded in this region.Probably populations in these small rivers were extinct, being vulnerable to changes in the environment, including general climate warming.

Figure 1 .
Figure 1.Distribution map and range boundaries of Phoxinus isetensis confirmed by morphological and genetic data along with other confirmed Phoxinus spp., whose distributions are partially within the glacier-covered area of the last glacial maximum.Locality numbers are designated in Suppl.materials 1, 5. * -by Palandačić et al. (2020); ** -by Palandačić et al. (2020) and Rothe et al. (2019).

Figure 2 .
Figure 2. BI consensus tree of concatenated COI and cytb mtDNA sequences representing available Phoxinus species in the NCBI data base combined with our data set.The numbers of some yet-unnamed clades are given according to the study of Palandačić et al. (2020).Phoxinus isetensis is highlighted with color.Bootstrap values/posterior probabilities above 70/0.7 are shown; asterisks represent 100/1 bootstrap/posterior probabilities values.The scale bar represents the expected substitutions per site.The nodes with multiple specimens were collapsed into a triangle, with the horizontal depth indicating the level of divergence within the node.

Figure 5 .
Figure 5. Morphological features of Phoxinus isetensis.A. Most frequent variant of the formula of pharyngeal bones: double-rowed formula 2.5-4.2,scale bar 0.5 mm; B. Ventral view of alizarin-stained female and male from the Bekshanka River (Volga basin).Female had 5 th type scalation on breast and belly, male had 6 th type.

Figure 7 .
Figure 7. PCA based on 41 morphometric characters for Phoxinus spp.-P.isetensis, P. chrysoprasius from the Crimean Peninsula, P. colchicus, and P. adagumicus from the Caucasus -and loading plot showing how strongly each character influences principal components.Samples of P. isetensis from the type locality (Severka River) are encircled by black.