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Molecular Phylogeny and Taxonomy of the Genus Mustela

Molecular Phylogeny and Taxonomy of the Genus Mustela

Mammal Study 33: 25–33 (2008) © the Mammalogical Society of

Molecular phylogeny and of the Mustela (, ), inferred from mitochondrial DNA sequences: New perspectives on phylogenetic status of the back-striped and American

Naoko Kurose1, Alexei V. Abramov2 and Ryuichi Masuda3,*

1 Department of Biological Sciences, Faculty of Science, Kanagawa University, Kanagawa 259-1293, Japan 2 Zoological Institute, Russian Academy of Sciences, Saint-Petersburg 199034, 3 Creative Research Initiative “Sousei”, University, Sapporo 060-0810, Japan

Abstract. To further understand the phylogenetic relationships among the mustelid genus Mustela, we newly determined nucleotide sequences of the mitochondrial 12S rRNA gene from 11 Eurasian of Mustela, including the domestic and the . Phylogenetic relationships inferred from the 12S rRNA sequences were similar to those based on previously reported mitochondrial cytochrome b data. Combined analyses of the two genes demonstrated that species of Mustela were divided into two primary clades, named “the small weasel group” and “the large weasel group”, and others. The (Mustela itatsi) formerly classified as a of the (M. sibirica), was genetically well-differentiated from M. sibirica, and the two species clustered with each other. The (M. lutreola) was closely related to “the ferret group” (M. furo, M. putorius, and M. eversmanii). Both the American mink of and the back-striped weasel (M. strigidorsa) of Southeast were more closely related to each other than to other species of Mustela, indicating that M. strigidorsa originated from an independent lineage that differs from other Eurasian . Based on biochemical, cytogenetic, and molecular differences as well as morphological evidence, it is proposed that the American mink be elevated to a distinct mustelid genus, .

Key words: American mink, mitochondrial DNA phylogeny, Mustela, Mustela strigidorsa, 12S rRNA.

The family Mustelidae, which consists of 59 species, is (M. nivalis), Malaysian weasel (M. nudipes), the most species rich family in the Carnivora European (M. putorius), Siberian weasel (M. (Wozencraft 2005). In this family, the genus Mustela sibirica) and back-striped weasel (M. strigidorsa). Some (mammalian group generally called ‘weasels’) is a poly- of these species have a Holarctic (M. erminea and M. typic genus widely distributed in , Northern nivalis) or a Eurasian (M. eversmanii, M. putorius and M. , Asia, North America, and northern parts of South lutreola) distribution. The distribution range of the other America. These small or middle-sized weasels occur in species is restricted to Asia (M. altaica, M. kathiah and diverse from tropical rainforests to and M. sibirica), and some species have small (or insular) from steppe and to riparian biotopes and coastal distribution areas (M. strigidorsa, M. nudipes, M. itatsi, waters. Mustela is the largest genus of Carnivora and is M. lutreolina). The American mink (M. vison) was comprised 17 species (Abramov 2000a; Wozencraft introduced to the Old World from North America, and 2005). In , 12 species of Mustela are known: naturalized in Eurasia: from the British Islands to Sibe- (M. altaica), ermine (M. erminea), ria, , and the Japanese Islands. (M. eversmanii), Japanese weasel (M. Relationships among the species of Mustela have not itatsi), yellow-bellied weasel (M. kathiah), European been fully clarified. The grouping of species within the mink (M. lutreola), Indonesian weasel (M. lutreolina), genus differ in the classifications of different authors.

*To whom correspondence should be addressed. E-mail: [email protected] 26 Study 33 (2008)

Some authors divided the genus Mustela into two genetic relationships among Mustela species, we newly (Ellerman and Morrison-Scott 1951; Heptner et al. determined partial sequences (about 960 base-pairs, bp) 1967), four (Pavlinov et al. 1995), or five subgenera of the 12S rRNA gene of the mitochondrial DNA (Youngman 1982; Anderson 1989). Recently, Abramov (mtDNA) genome from 11 species of Mustela of Eura- (2000a) divided this genus to nine subgenera and re- sia, including the domestic ferret and the American garded the American mink as a separate genus, Neovison. mink. The poorly studied back-striped weasel (M. Many studies have been performed to understand the strigidorsa) from Southeast Asia was included in the phylogenetic relationships within this group. These genetic study for the first time. Combining the data with studies are based upon the analysis of morphological char- previously reported cytochrome b gene data, we present acters (Youngman 1982; Anderson 1989; Baryshnikov here the molecular phylogeny of Eurasian representa- and Abramov 1997; Abramov 2000a), biochemical data tives of Mustela and discuss evolutionary and taxonomic (Belyaev et al. 1980; Taranin et al. 1991) and genetic relationships among species. data (Graphodatsky et al. 1976; Lushnikova et al. 1989; Masuda and Yoshida 1994a; Davison et al. 1999, 2000; Materials and methods Hosoda et al. 2000; Kurose et al. 2000a; Sato et al. 2003). However, the overall phylogeny of Mustela is still Samples and DNA extraction unresolved. Species of Mustela examined are listed in Table 1. In the present study, to further understand the phylo- Muscle tissue from were preserved in 70–100%

Table 1. Profiles of samples examined in the present study

& Code Chromosome Sampling locality Accession Number Species Common name # Tissue (individual no.) No. (2n) if known 12S rRNA Cytochrome b Mustela nivalis Least weasel MNI (5) 42# muscle Hokkaido, Japan AB119065 AB026106* (38$) Mustela altaica Mountain weasel MAL (RMNG1) 44# muscle Great Hingan Mts, AB119064 AB026100* (ZIN C.83033)@ Mustela erminea Ermine MER (1) 44# muscle Hokkaido, Japan AB119066 AB026101* Mustela itatsi Japanese weasel MIT (MR1) 38$ muscle Iwate, Japan AB119071 AB026104* Mustela sibirica Siberian weasel MSI (KYO1) 38# muscle Kyoto, Japan AB119072 AB026108* Mustela Steppe polecat MEV (RURA1) 38# muscle Chelyabinsk Province, AB119068 AB026102* eversmanii Russia (ZIN O.34843)@ Mustela putorius MPU (RLEN1) 40# muscle Leningrad Province, AB119067 AB026107* Russia (ZIN O.34838)@ Mustela furo Ferret MFU (2) 40! hair Domestic AB119069 AB026103* Mustela lutreola European mink MLU (RPSK1) 38# muscle Pskov Province, AB119070 AB026105* Russia (ZIN C.55065)@ Mustela Back-striped weasel MST (1) – muscle Vinh Phuc Province, AB119073 AB119078 strigidorsa Vietnam (ZIN C.85042)@ Mustela vison American mink MVI (1) 30# muscle Domestic AB119074 AB026109* Martes melampus Japanese MME (1) 38$ muscle Iwate, Japan AB119075 AB012351* Martes zibellina MZI (1) 38+ muscle Hokkaido, Japan AB119076 AB012360* anakuma Japanese MEL (K6) 44$ muscle Kitakyushu, Japan AB119077 AB049800** # Cited from Graphodatsky et al. (1976). $ Obara (1991) reported 38 chromosomes specific to the population of the Island (Japan). + Cited from Graphodatsky et al. (1977). ! Cited from Fredga and Mandahl (1973). @ Specimen no. of Zoological Institute of Russian Academy of Sciences, St. Petersburg (ZIN). & The nucleotide sequence data reported in the present study will appear in the DDBJ, EMBL, and GenBank nucleotide sequence databases with these accession numbers. * Cited from Kurose et al. (2000a). ** Cited from Kurose et al. (2001). Kurose et al., Molecular phylogeny of Mustela 27 ethanol at room temperature until use. As outgroup, the using the cycle labeling system Catalyst (Perkin-Elmer (Martes melampus), sable (Martes Cetus) and sequenced using the ABI PrismTM 377 auto- zibellina) and (Meles anakuma) were mated sequencer. analyzed in addition to cytochrome b (accession no. X82296) and 12S rRNA (AY012149) sequences of the Sequence analysis domestic ( catus). Total genomic DNAs were Sequence alignment was done using the GeneWorks extracted using the phenol/proteinase K/sodium dodecyl computer software (Intelligenetics). Molecular phylo- sulfate method of Sambrook et al. (1989) with some genetic analyses were perfomed using PAUP* version simplified modifications as indicated by Masuda and 4.0b10 (Swofford 2001). The phylogenetic trees were Yoshida (1994b). DNA extracts of M. lutreola (muscle constructed by three methods: neighbor-joining (NJ: tissues preserved in 70% ethanol for about 30 years) Saitou and Nei 1987) using Kimura’s (1980) two- and M. altaica (muscle tissues preserved in 70% ethanol parameter distances, maximum parsimony (MP) and the for about 100 years) were concentrated to approximate- maximum likelihood (ML). Because phylogenetic rela- ly 100 fold using Centricon-30 microconcentrators tionships of species were very similar among separate (Amicon), because these tissues contained fragmented analyses of cytochrome b and 12S rRNA as well as DNAs. DNA from hairs was extracted from M. furo analyses in which the two genes were combined, we using the method of Walsh et al. (1991). An aliquot (1– used the combined sequences (about 2,110 bp) and 10 µl) of each DNA extract was used as template for excluded insertions or deletions (indels) for analysis. the subsequent polymerase chain reaction (PCR). The MP trees were obtained using the heuristic search option with random sequence addition and TBR (tree- PCR amplification and direct sequencing bisection-reconnection) branch swapping. All sites were The sequences of the 12S rRNA gene of all samples treated as unordered and equally weighted. For the ML were PCR-amplified using two primers (L5' and H3') analysis, we selected the best-fitting model of molecular quoted from Ledje and Arnason (1996). Sequencing evolution using the program Modeltest 3.06 (Posada primers were newly designed as follows: M-12S-F2 and Crandall 1998). This test chose GTR (general time 5'-GCCACCGCGGTCATACGATTA-3'; M-12S-F3 5'- reversible; Tavaré 1986) model of substitution taking CCCTCTAGAGGAGCCTGTTCT-3'; M-12S-R2 5'-AT- account of the proportion of invariable sites (0.4182) TAACAGTAGCTTTTTACRGCCTTG-3'; M-12S-R3 5'- and following a gamma distribution shape parameter of GGTTTGCTGAAGATGGCGGTAT-3'. The complete 0.6382 (GTR + I + G). In the rate matrix of this substi- sequence of the cytochrome b gene of one sample of tution model, the rates of substitutions were estimated as M. strigidorsa was PCR-amplified and sequenced using 1.8378 for A-C, 12.2455 for A-G, 2.0966 for A-T, the method of Kurose et al. (2000a). Cytochrome b 0.2885 for C-G, 24.2007 for C-T, and 1.000 for G-T. sequences of the other Mustela species were obtained Bootstrap values (Felsenstein 1985) were derived from from Kurose et al. (2000a) and the accession numbers 1,000 replications in both MP and NJ, and 200 replica- are shown in Table 1. The PCR amplifications were per- tions in ML to assess the confidence of the trees. formed in 50 µl reaction volumes. In cases of aged sam- ples where PCR was inhibited, 20 µg of bovine serum Results albumin (Boehringer) was added to the reaction mixture. Thirty-five cycles of amplification were performed with Nucleotide sequences of the partial 12S rRNA gene the following programs using a DNA thermal cycler (about 960 bp) from the 14 species of Mustelidae and the (PJ2000, Perkin-Elmer Cetus): denaturing 94°C for 1 complete cytochrome b gene (1,140 bp) from Mustela min; annealing 50°C for 1 min; extension 72°C for 2 strigidorsa were obtained in the present study. Table 1 min, and then the reaction was completed at 72°C for 10 shows accession numbers of the newly generated nucle- min. To check PCR amplification, 10 µl of the PCR otide sequences. The sequence alignment of the 14 mus- product was electrophoresed on a 2% agarose gel, telid taxa showed that 231 sites in the 12S rRNA gene stained by ethidium bromide, and visualized under an and 370 sites in the cytochrome b gene were variable. ultraviolet illuminator. The remaining 40 µl of each Because phylogenetic trees reconstructed separately PCR product was purified with the QIAquick purifica- from cytochrome b and 12S rRNA genes formed very tion kit (Qiagen). Purified PCR products were labeled similar topologies, we combined the two genes (2,111 28 Mammal Study 33 (2008)

Fig. 1. Phylogenetic trees of combined sequences of 12S rRNA and cytochrome b genes, constructed using the maximum likelihood method (ML). Numbers near internal branches were bootstrap values of ML (200 replications), the maximum parsimony method (MP; 1,000 replications), and the neighbor-joining method (NJ; 1,000 replications), respectively. Details of analysis conditions were described in the text. Mu, Mustela; Ma, Martes; Me, Meles. bp) for analysis. From the 2,111-bp sequences, 32 bp sibirica was split in ML and MP, the bootstrap values to were excluded as indel sites, leaving 2,079 bp. Phyloge- support the relationship were low (78% and 62%, respec- netic relationships from the combined analysis of the two tively; Fig. 1). These two species were not clustered in genes are almost same among ML, MP, and NJ methods, the NJ tree. The genetic differentiation between M. itatsi so that we showed the ML tree as respresentative. Boot- and M. sibirica corresponded to those between other dis- strap values estimated from the three methods are indi- tinct species. In addition, M. lutreola and the “ferret cated on the ML tree (Fig. 1). group (M. putorius, M. eversmanii, and M. furo)” were For the MP analysis, 394 of 2,079 sites were parsimo- closely related to each other and clustered with 99 or niously informative. The consistency index (CI) was 100% bootstrap values having small genetic distances. 0.6368, the retention index (RI) was 0.5483, and the The domestic ferret (M. furo) examined was closer to M. rescaled consistency index (RC) was 0.3491. eversmanii than to M. putorius. The three genera of Mustela, Martes and Meles were clearly separated. In the genus Mustela, both M. vison Discussion and M. strigidorsa were first to split from the other Mustela species and clustered with 86/79/71% (ML/MP/ Phylogeny of the large weasel group NJ) bootstrap values. The genetic distances between Morphological classification (Youngman 1982; both M. vison + M. strigidorsa and the other Mustela spe- Wozencraft 1989; Pavlinov et al. 1995) as well as karyo- cies were higher than those among the rest of Mustela. taxonomy (Graphodatsky et al. 1976) supported a close Mustela erminea was the next split from the rest of relationship between Mustela lutreola and M. sibirica. the species. Mustela altaica and M. nivalis were clus- The comparative analysis of antigenic structures of the tered with 94/85/89% bootstrap values: the cluster was immunoglobulin chain in Mustelidae (Taranin et al. named the “small weasel group” (Fig. 1). The other spe- 1991) showed that M. lutreola was closer to the ferret cies (eversmanii, putorius, furo, lutreola, sibirica, and group than to M. sibirica. According to Abramov itatsi) formed a clade (named the “large weasel group”). (2000a), M. lutreola belongs to the separate subgenus Although, within this group, a clade of M. itatsi and M. Lutreola which is equidistant to (subgenus Kurose et al., Molecular phylogeny of Mustela 29

Putorius) and M. sibirica (subgenus Kolonokus). The putorius, M. eversmanii, and M. furo (Fig. 1) support- molecular phylogeny of the present study suggests that ing previous results that the parental species of the M. lutreola is nested between “the ferret group” and the domestic ferret were these polecat species. The genetic “M. itatsi + M. sibirica” lineage of the “large weasel differentiation was the same as the level of intra-spe- group”. Davison et al. (1999, 2000) reported that M. cific variations of other mustelids. The closer relation- lutreola was included in the ferret group cluster compris- ship between M. eversmanii and M. furo obtained in the ing M. furo, M. putorius, and M. eversmanii, judging present study suggests that M. eversmanii is a possible from the molecular phylogeny of partial cytochrome b ancestor of the . Further analyses of karyo- sequences (337 bp). The partial sequence (Accession types, mtDNA and nuclear DNA, and morphology of No. AF068544) reported by Davison et al. (1999) was the from different lineages as well as the wild identical with the homologous region within the com- populations of polecats would more precisely illuminate plete cytochrome b sequences obtained through our pre- the history of the ferret’s domestication. vious study (Kurose et al. 2000a). The difference of position of M. lutreola may be ascribed to the short un- Phylogenetic positions of the Japanese weasel M. itatsi informative sequence (337 bp) used by Davison et al. and the Siberian weasel M. sibirica (1999). The taxonomic relationship between M. itatsi and M. sibirica has been obscure for a long time. Usually M. Parental species of the domestic ferret M. furo itatsi is considered conspecific to M. sibirica (Ellerman The domestic ferret (M. furo) is generally thought to and Morrison-Scott 1951; Youngman 1982; Wozencraft be domesticated from M. putorius, or from its congener, 1989; Corbet and Hill 1992; Pavlinov et al. 1995). M. eversmanii. The diploid chromosome number is 2n = Recently, Abramov (2000b) reported that cranial differ- 40 for M. putorius as well as M. furo, while 2n = 38 for ences between these two taxa are greater than geographic M. eversmanii. The former two taxa have morphologi- variations among M. sibirica populations from , cally identical chromosome sets, but the karyotype of , and Japan. Masuda and Yoshida M. eversmanii differs from those of the formers by a sin- (1994b) and Kurose et al. (2000a) based on cytochrome gle Robertsonian rearrangement (Volobuev et al. 1974). b sequences revealed that there is a relatively large The traits of developmental biology of M. furo were genetic distance between M. itatsi and M. sibirica. The reported to be more similar to M. putorius than to M. karyotypical differences were found between the two eversmanii (Ternovsky 1977). Meanwhile, Blandford weasels (Kurose et al. 2000b), although both shared the (1987) suggested that M. eversmanii has a superficially identical diploid chromosome number (2n = 38). In ML more similar cranial morphology with the domestic and MP trees, M. itatsi and M. sibirica were clustered ferret. Experimental hybridization among M. furo, M. with each other. In the NJ tree, however, these taxa putorius, and M. eversmanii was found to be possible, show successive splittings, with M. itatsi was the first to and all hybrids were fertile (Ternovsky 1977; Ternovsky split (Fig. 1). The transversional difference of the third and Ternovskaya 1994). Based on partial cytochrome b codon positions (0.79%) between M. itatsi and M. sequences and control region fragment analysis, Davison sibirica refers to a divergence time of about 1.6 million et al. (1999) investigated the phylogenetic relationships years ago (Table 2) according to the transversional rate among M. putorius, M. furo and M. eversmanii in com- (0.5%/million years) of mammalian cytochrome b of parison to some species of Mustela. Two geographically Irwin et al. (1991). The ancestor of M. itatsi might distinct polecat lineages were found in Britain, where have been derived from M. sibirica probably in conti- one may be ancestral to the British polecat, and the other nental Asia in the early . After that, a certain to the domestic ferret. However, the wild source of the ancestral population of M. itatsi might have immigrated ferret remains obscure. Davison et al. (1999) suggest to the Japanese islands, and then it could have been that the relatively recent from M. lutreola and isolated on the islands through the strait formation. The M. nigripes, and the effects of polecat-ferret hybridiza- other ancestral populations remaining on the continent tion result in an unresolved molecular phylogeny among might have been extinct. Alternatively, from an ancestor these species. common to M. sibirica, M. itatsi might have evolved The present study revealed the close relationships independently on the Japanese islands after their separa- among the three morphologically similar taxa, M. tion from the continent. 30 Mammal Study 33 (2008)

Phylogeny of the small weasel group the specimen for this was of the European Most authors unite small weasels (M. altaica, M. mink Mustela lutreola. At present, the valid genus erminea and M. nivalis) in the subgenus Mustela name is Neovison Barysnikov and Abramov, 1997. (Ellerman and Morrison-Scott 1951; Heptner et al. During the last decades, the presence of large differ- 1967; Youngman 1982; Nowak 1991; Pavlinov et al. 1995). ences in biochemical, cytogenetic, and molecular charac- Abramov (2000a) placed the ermines (M. erminea and teristics between the American mink and the other North American M. frenata) in the subgenus Mustela, Mustela species have been reported. For example, the whereas other small weasels (M. altaica, M. nivalis, and diploid chromosome number of the American mink is 2n M. kathiah) were placed in the separate subgenus Gale. = 30, whereas those of the other Mustela species ranges In the present study, the divergence time between M. from 38 to 44. Graphodatsky et al. (1976) examined erminea and the other Mustela species (except M. vison) karyotaxonomy among seven species of Mustela, and was estimated around 3–5 million years ago (Table 2). considered that the American mink first split from the Thus, species diversification within Mustela might have other Mustela species. Belyaev et al. (1980) provided a started from the end of the Miocene to the . comparative immunochemical study of serum proteins The result that M. erminea first split from the other for Mustela species such as M. lutreola, M. putorius, M. Mustela species is supported by the karyological study eversmanii, M. sibirica, M. altaica, M. nivalis, M. (Graphodatsky et al. 1976; Obara 1991) that M. erminea, and M. vison. The American mink was sharply erminea is the more ancestral form among Eurasian detached from the other species of Mustela and had Mustela. closer immunological affinities to the sable Martes The closer relationship between M. altaica and M. zibellina. These results were confirmed by Taranin et nivalis indicated in the present study was also supported al. (1991) in comparative analysis of antigenic structures by morphological classification (Heptner et al. 1967; of immunoglobulins. A comparative study of chemical Youngman 1982; Wozencraft 1989; Abramov 2000a) composition of anal sac secretion in mustelids (Brinck et and karyotaxonomy (Graphodatsky et al. 1976) as well al. 1983) showed that the American mink is separated as molecular phylogeny: cytochrome b (Kurose et al. from other Mustela species as much as other analyzed 2000a); cytochrome b and nucler DNA (Sato et al. genera (Martes, and Meles). Lushnikova et al. 2003); and nuclear DNA (Sato et al. 2004, 2006). The (1989) examined the patterns of blot-hybridization of bootstrap values supporting the two species’ clade in the cloned BamHI repeats to genome DNAs for estimation present study were larger than those in the previous of the phylogenetic relationships among some Mustela molecular studies mentioned above. The two species species (M. lutreola, M. putorius, M. sibirica, M. erminea, were estimated to have diverged > 5 million years ago and M. vison). They found a distant position of the (at the end of the Miocene) (Table 2). American mink from the other species as well as the Vormela peregusna. Recent studies of Phylogenetic positions of the American mink nucleotide sequences of the mtDNA cytochrome b gene The phylogenetic and taxonomic position of the (Masuda and Yoshida 1994a; Davison et al. 1999; American mink has long been unclear. The phylogenetic Hosoda et al. 2000; Kurose et al. 2000a) and of the relationships between the American mink and the Euro- nuclear interphotoreceptor retinoid binding protein gene pean mink has been questioned for years, with many sci- (Sato et al. 2003, 2004) also showed the high level of entists believing them to be conspecific or at least closely divergence between the American mink and the other related. The morphological resemblance and similar species of Mustela. On the composite super-tree for mode of life of American and European provide Mustelidae by Bininda-Emonds et al. (1999), the Ameri- evidence to group them in the subgenus Lutreola can mink was separate from all Mustela species. (Walker 1964; Heptner et al. 1967; Ternovsky and There are remarkable cranial differences between the Ternovskaya 1994). Most authors now place the American mink and all Mustela (Youngman 1982; American mink in the separate subgenus Vison Gray, Abramov 2000a). The American mink has a small 1865 of genus Mustela (Youngman 1982; Nowak 1991; incipient metaconid on M1 (lower first molar), the wide 1 Pavlinov et al. 1995; Baryshnikov and Abramov 1997; talonid of M1 with lingual rim, large M (upper first Lariviere 1999). According to the International Code of molar) with the extended lingual lobe, and large two- Zoological Nomenclature, this name is invalid because rooted Pm2 (upper second premolar). The lateral part of Kurose et al., Molecular phylogeny of Mustela 31

Table 2. Percentage differences of transversions at the third codon positions of the cytochrome b sequences (above diagonal) and the estimated divergence time (million years, below the diagonal) using the transversional substitution rate (0.5%/million years) at the third codon positions of mammalian cytochrome b reported by Irwin et al. (1991).

Code*123456789101112131415 1. MAL – 2.89 2.63 2.63 2.37 2.63 2.37 2.63 2.37 6.84 5.53 8.42 7.89 11.58 18.68 2. MNI 5.78 – 2.37 2.37 2.11 2.37 2.11 2.37 2.11 5.53 5.79 8.16 7.63 11.84 17.89 3. MER 5.26 4.74 – 2.11 1.84 2.11 1.84 2.11 1.84 5.26 5.00 8.42 7.89 11.05 17.63 4. MPU 5.26 4.74 4.22 – 0.26 0.53 0.26 0.53 0.79 5.79 4.47 7.37 6.84 9.47 17.63 5. MEV 4.74 4.22 3.68 0.52 – 0.26 0 0.26 0.53 5.53 4.21 7.63 7.11 9.74 17.89 6. MFU 5.26 4.74 4.22 1.06 0.52 – 0.26 0.53 0.79 5.79 4.47 7.89 7.37 10.00 18.16 7. MLU 4.74 4.22 3.68 0.52 0 0.52 – 0.26 0.53 5.53 4.21 7.63 7.11 9.74 17.89 8. MIT 5.26 4.74 4.22 1.06 0.52 1.06 0.52 – 0.79 5.79 4.47 7.89 7.37 9.47 17.63 9. MSI 4.74 4.22 3.68 1.58 1.06 1.58 1.06 1.58 – 5.53 4.74 8.16 7.63 10.26 18.42 10. MST 13.68 11.06 10.52 11.58 11.06 11.58 11.06 11.58 11.06 – 5.53 10 9.47 12.63 18.68 11. MVI 11.06 11.58 10.00 8.94 8.42 8.94 8.42 8.94 9.48 11.06 – 8.68 8.16 9.74 20.00 12. MME 16.84 16.32 16.84 14.74 15.78 15.78 15.26 15.78 16.32 20.00 17.36 – 0.53 9.47 17.11 13. MZI 15.78 15.26 15.78 13.68 13.68 14.74 14.22 14.74 15.26 18.94 16.32 1.06 – 8.95 16.58 14. MEL 23.16 23.68 22.10 18.94 19.48 20.00 19.48 18.94 20.52 25.26 19.48 18.94 17.90 – 18.68 15. FCA** 37.36 35.78 35.26 35.26 35.78 36.32 35.78 35.26 36.84 37.36 40.00 34.22 37.36 33.16 – * Codes refer to those in Table 1. ** FCA (Felis catus) was used for outgroup. auditory bullae near the meatus forms a structure resem- only as sighting and distribution reports (Lekagul and bling the meatal tube. Some of these cranial characters McNeely 1988; Duckworth et al. 1999). This species is are typical for the genus Martes (Youngman 1982; distributed in the (from eastern to Abramov 2000a) and probably are plesiomorphic for Assam), Burma, northern , southern China, (see Bryant et al. 1993). and Vietnam. According to Schreiber et al. (1989) The molecular phylogeny in the present study also only about 30 museum specimens exist of this rare spe- demonstrated that the American mink was separate from cies. Usually M. strigidorsa has been included in the the other Mustela species. The genetic distances between subgenus Lutreola together with M. lutreola and M. the American mink and the other species of Mustela sibirica (Youngman 1982; Nowak 1991; Pavlinov et al. nearly corresponded to those between the Mustela spe- 1995). Some authors united M. strigidorsa and M. cies and other mustelid genera such as Martes and Meles nudipes in the subgenus Pocockictis (Gray 1865; Pocock (Fig. 1). Using the molecular clock of cytochrome b 1921, 1941). According to Abramov (2000a), M. (Table 2), the American mink was estimated to have strigidorsa is one of the most morphologically differ- diverged from the other Mustela species approximately entiated species in Mustela (except the American mink). 8–11 million years ago as described in Kurose et al. Based on morphological characters, he placed M. (2000a). Based on the biochemical, cytogenetic, and strigidorsa in the separate subgenus Cryptomustela. molecular differences as well as morphological evidence, The present study reports the mtDNA sequence data we therefore recommend that the American mink be on M. strigidorsa for the first time and revealed a large classified in a distinct mustelid genus, Neovison. genetic divergence between M. strigidorsa and other The divergence times within Mustela estimated in the Mustela. This result leads to a possibility that two present study are not discordant with the data of Sato et distinct lineages of Eurasian weasels exist, and M. al. (2003). strigidorsa belongs to the independent Southeast Asian lineage which differs from other Eurasian weasels. This Phylogenetic position of the back-striped weasel M. taxon probably split early from the Mustela stock and strigidorsa evolved independently at the edge of distribution range The back-striped weasel (M. strigidorsa) is one of the of the genus. Unfortunately the fossil history of M. rarest and most poorly studied species among Mustelidae strigidorsa is absolutely unknown. This species differs in the world. Information on this elusive weasel exists from other Mustela in the unique coloration of the body 32 Mammal Study 33 (2008) and structure. However, as a whole, the Footed Ferret. Pp. 10–20. Yale University Press, New Haven and characters (shape and size of cranium, mandible and den- . Baryshnikov, G. F. and Abramov, A. V. 1997. Structure of baculum tition) of this species are similar to those of other large- (os penis) in Mustelidae (Mammalia, Carnivora), Communication sized Mustela, in contrast to the American mink. 1. Zoologicheskii Zhurnal 76: 1399–1410 (in Russian with Our analysis suggests the genus Mustela may be para- English abstract). Belyaev, D. K., Baranov, O. K., Ternovskaya, Yu. G. and Ternovsky, phyletic with respect to the American mink (as Neovison D. V. 1980. A comparative immunochemical study of serum pro- vison). This result would indicate the necessity of teins in the Mustelidae (Carnivora). Zoologicheskii Zhurnal 59: taxonomic revision with the inclusion of all Mustela 254–260 (in Russian with English abstract). species. To infer the phylogenetic relationship and the Bininda-Emonds, O. R. P., Gittleman, J. L. and Purvis, A. 1999. Building large trees by combining phylogenetic information: a molecular evolution of M. strigidorsa, it is necessary to complete phylogeny of the extant Carnivora (Mammalia). Bio- investigate the Southeast Asian weasels, especially the logical Reviews 74: 143–175. Malayan weasel M. nudipes. It is also important to Blandford, P. R. S. 1987. Biology of the polecat Mustela putorius: a literature review. Mammal Review 17: 155–198. include the South American weasels M. africana and M. Brinck, C., Erlinge, S. and Sandell, M. 1983. Anal sac secretion in felipei, for which no genetic data is available at present. mustelids a comparison. Journal of Chemical Ecology 9: 727– The present study revealed the phylogenetic relation- 745. ships among Eurasian species of the genus Mustela. The Bryant, H. N., Russel, A. P. and Fitch, W. D. 1993. Phylogenetic rela- tionships within the extant Mustelidae (Carnivora): Appraisal of results provide not only invaluable insight to reconstruct the cladistic status of the Simpsonian subfamilies. Zoological the taxonomy of the Mustelidae, but also useful informa- Journal of Linnean Society 108: 301–334. tion to survey genetic characteristics and hybridization Corbet, G. B. and Hill, J. E. 1992. The of the Indomalayan Region: A Systematic Review. Oxford University Press, Oxford, problems between native populations and introduced 488 pp. populations for considering species conservation. In Davison, A., Birks, J. D. S., Griffiths, H. I., Kitchener, A. C., Biggins, addition, further study involving other Mustelidae spe- D. and Butlin, R. K. 1999. Hybridization and the phylogenetic cies of Eurasia and both North and would relationship between polecats and domestic ferrets in Britain. Biological Conservation 87: 155–161. illuminate the worldwide evolution of Mustelidae. 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