Systematic position

The European mink Mustela lutreola belongs to the class of Mammalia, the order of Carnivora, the suborder of Caniformia, the superfamily of Musteleoidea, the family of Mustelidae, the subfamily of Mustelinae the genus of Mustela.

The first confirmed reference to the European mink comes from the work of G. Agricola “De Ammantibus Subterraneis Liber”, in which it was called noerza, while the first scientific name of the species was proposed by Leche – Viverra fusca, ore alba. The first mention of a species in modern times is most likely incorrectly attributed to St. Albert the Great. The modern scientific name in the binomial system was proposed by Linnaeus in 12th edition of his work “Systema Naturae”.

In the first version, as Viverra lutreola, the Latin binomial name appeared in his earlier work – “Fauna Svecica”. There were other synonyms of the binominal name of the species used in the past, for example: Lutra minor, Lutra lutreola, Putorius lutreola, Foetorius lutreola, Lutreola lutreola, Martes lutreola, Vison lutreola, Hydromustela lutreola, Lutreola europeae, Mustela wyborgensis. The scientific Polish name of the Latin species, besides the widely accepted form of “norka europejska” (European mink), sometimes – particularly in the Russian scientific and cultural sphere of influence – has been replaced by the form “norka rosyjska” (Russian mink). The first comprehensive, scientific description of the European mink was published by Leche, and a comprehensive bibliography of the species, covering works published until 1990, was compiled by Youngman.
The original vernacular name in Polish (phonetically probably also in other Slavic languages) appeared in two forms feminine nurka, and masculine nurek (meaning “diver”), and its source is a verb nurkować (“to dive”) or nurzać (“to plunge”). The plural noun nórki, defining the type of precious fur, was used in the old Polish language, appearing for the first time in the sources written in 1562. From the Polish name comes the common name of the European mink in German – nerz (formerly nörz) and Latin – noerza. The feminine form nurka, nowadays completely abandoned, was used in Polish literature even in the first half of the 20th century. The equivalent of the Latin binominal scientific name previously used in Polish language was wyderka błotna (literally: a tiny marshy otter) (aptly translating the diminutive expressed in the species epithet lutreola), as well as łasica nurka (literally: a weasel diver) (correct name as far as the translation of genus name is concerned) and wydra mała (literally: a small otter).

Due to the same ecological niche, the European mink and the American mink Neovison vison show significant similarities: ecological (similar food and habitat), behavioral (similar social structure, lifestyle, locomotor characteristics, instinctive behavior), and morphological (approximate size and general body plan). These similarities caused that traditionally both species were included in a common genus, although this classification system, is now considered outdated. The reason for this state of things is the incidental and secondary nature of the similarities of both species that evolved independently (convergence evolution), in complete genetic isolation. It should be emphasized here that besides very significant genetic and phylogenetic differences, there are also many phenotypic differences between the two species (the differences between the European mink and the American mink are described in a separate chapter).

The present systematic position of the European mink is the result of the phylogenetic molecular analysis of species within the Mustelidae family. The phylogenetic analysis, based on the nucleotide sequence of nuclear gene (gene of interphotoreceptor retinoid binding, itbp), and the nucleotide sequence of mitochondrial gene (gene of cytochrome b, cytb), performed by Sato et al. proved the belonging of the M. lutreola species in the clade including also the European polecat (Mustela putorius), the steppe polecat (Mustela eversmanii), the Siberian weasel (Mustela sibirica) and the Japanese weasel (Mustela itasi). The results of this study confirm the results of a phylogenetic analysis based on the sequences of mitochondrial genes – 12S rRNA, cytb and the gene encoding the NADH dehydrogenase subunit 2 and the nuclear genes – the gene for the thyroxine-binding globulin, irbp and the transthyretin-encoding gene.

The multi-gene phylogenetic studies conducted by Flynn, based on the fragments of sequence of the abovementioned three mitochondrial genes and three nuclear genes, are particularly interesting. The results of these studies indicate that the European polecat is phylogenetically the closest species to the European mink, while other close species include: The Siberian weasel, the least weasel (Mustela nivalis) and the stoat (Mustela erminea). The close evolutionary relationship between the European mink, the European polecat and the steppe polecat is also evidenced by the results of the studies by Davison et al., based on mitochondrial sequence of cytb gene and the D loop. At the same time, it was proved that the evolutionary relationship between the European mink and the American mink is significantly less expressed.

In the past, the European mink was classified by various authors within genus Viverra, Putorius, Lutra, Martes, Hydromustela, Lutreola, and finally Mustela. As early as the first half of the twentieth century, the inconvenience of taxonomic relationships within the traditionally defined Mustela genus was pointed out, particularly with respect to the taxonomic position of M. lutreola in reference to the position of N. vison (then Mustela vison), M. putorius and M. sibirica. Even before the separate Neovison genus was established, it was proposed to separate them into two subgenera within the Mustela genus to emphasize the differences between the two ecologically twin species. According to this a system, the European mink was classified as a representative of the subgenus Lutreola, while the American mink was included in the subgenus Vison Gray, 1843, and finally Neovison Baryshnikov & Abramov, 1997. This approach was supported by the results of karyological, immunological, odontological and craniological studies conducted in the 1970s and 1980s. López-Giráldez et al. developed a simple genetic test based on the PRC-RFLP technique for microsatellite sequence, which in the case of the N. vison contains 213-stonucleotide insertion type SINE (short interspersed nuclear elements) and allows differentiation of the European mink, the American mink and the European polecat. It should be emphasized that the estimated genetic distance between N. vison and the representative of Mustela genus (including M. lutreola) is comparable to the genetic distance between the species of Mustela genus and the species of Martes and Meles genera.

The controversies surrounding the systematic position of the European mink have not ceased and there is still a lack of consensus, primarily on the issue of reflection of the actual phylogenetic relationships between M. lutreola and M. putorius and M. eversmani. It is expected that with the increase in the availability of the Next Generation Sequencing (NGS), and hence the number of phylogenetic analyzes conducted on the genomic (multigene, multilocus) scale, it will be necessary to revise the taxonomic classification of M. lutreola, as well as other representatives of the Mustelidae family. This is demonstrated, for example, by the proved deficiency of the cytochrome b gene as a phylogenetic marker for the Mustelidae.

As far as taxonomic units lower than species are concerned, it is postulated to distinguish six or seven subspecies of the European mink: M. l. lutreola L., 1761, M. l. biedermanni Matschie, 1912, M. l. binominata Ellerman & Morrison-Scott, 1951, M. l. cylipena Matschie, 1912, M. l. novikovi Ellerman & Morrison-Scott, 1951, M. l. transsylvanica Éhik, 1932, M. l. turovi Kuznetsov & Novikov, 1939. The features of the proposed subspecies are presented in the chapter on the geographic differentiation of the European mink.

The currently accepted system of classification of the European mink is confirmed by the results of research on the hybridization of this species with other species of the Mustela genus. Numerous field observations and experimental studies have demonstrated the possibility of hybridization between the European mink and the European polecat, both in laboratory and natural conditions. The possibility of crossbreeding between the European mink and the ferret Mustela putorius furo has also been reported. Natural cases of this type of hybridization are, however, sporadic. At the same time, it was proved there is no possibility of crossbreeding between the European mink and the American mink or Siberian weasel. Hybrid embryos for of these species obtained in laboratory conditions exhibited pathological characteristics and were resorbed in a short time.