Genus Mustela Research Articles

First record of a white phenotype Egyptian weasel (Mustela subpalmata) in Tahta, Sohag, Egypt

Abstract Aberrant pelage colourations have been occasionally detected in carnivores, including mustelids. However, to our knowledge, no cases of leucism have been reported in the genus Mustela to date. On May 1, 2024, an Egyptian weasel (Mustela subpalmata) killed by locals was discovered and photographed in the town of Tahta, Egypt. The specimen exhibited predominantly white fur on its left side and head. Although eye colour was not inspected, the normal lip colouration, dirty white fur hue, and dark brown tail tip suggest a case of leucism rather than albinism. Leucism is often linked to inbreeding caused by population isolation or size reduction, which could arise through urban development, considering that roads can act as social and physical barriers to gene flow. Genetic studies are needed to elucidate the population dynamics and conservation implications for urban Egyptian weasels.

Evolutionary characteristics of the mitochondrial NADH dehydrogenase subunit 6 gene in some populations of four sympatric Mustela species (Mustelidae, Mammalia) from central Europe.

Selection on or reticulate evolution of mtDNA is documented in various mammalian taxa and could lead to misleading phylogenetic conclusions if not recognized. We sequenced the MT-ND6 gene of four sympatric Mustelid species of the genus Mustela from some central European populations. We hypothesised positive selection on MT-ND6, given its functional importance and the different body sizes and life histories of the species, even though climatic differences may be unimportant for adaptation in sympatry. MT-ND6 genes were sequenced in 187 sympatric specimens of weasels, Mustela nivalis, stoats, M. erminea, polecats, M. putorius, and steppe polecats, M. eversmannii, from eastern Austria and of fourteen allopatric polecats from eastern-central Germany. Median joining networks, neighbour joining and maximum likelihood analyses as well as Bayesian inference grouped all species according to earlier published phylogenetic models. However, polecats and steppe polecats, two very closely related species, shared the same two haplotypes. We found only negative selection within the Mustela sequences, including 131 downloaded ones covering thirteen species. Positive selection was observed on three MT-ND6 codons of other mustelid genera retrieved from GenBank. Negative selection for MT-ND6 within the genus Mustela suggests absence of both environmental and species-specific effects of cellular energy metabolism despite large species-specific differences in body size. The presently found shared polymorphism in European polecats and steppe polecats may result from ancestral polymorphism before speciation and historical or recent introgressive hybridization; it may indicate mtDNA capture of steppe polecats by M. putorius in Europe.

Non‐invasive methods for monitoring weasels: emerging technologies and priorities for future research

Abstract Weasels (genus Mustela and Neogale) are of management concern as declining native species in some regions and invasive species in others. Regardless of the need to conserve or remove weasels, there is increasingly a need to use non‐invasive monitoring methods to assess population trends. We conducted a literature review and held the first ever International Weasel Monitoring Symposium to synthesise information on historical and current non‐invasive monitoring techniques for weasels. We also explored current limitations, opportunities, and areas of development to guide future research and long‐term monitoring. Our literature search revealed that in the past 20 years, camera traps were the most commonly used non‐invasive monitoring method (62% of studies), followed by track plates or scent stations designed to collect footprints (23%) and walking transects for tracks in snow or soil (8.7%). Experts agreed that the most promising non‐invasive monitoring techniques available include use of citizen scientist reporting, detection dogs, detecting tracks, non‐invasive genetic surveys, and enclosed or unenclosed camera trap systems. Because each technique has benefits and limitations, using a multi‐method approach is likely required. There is a need for strong commitment to dedicated monitoring that is replicated over space and time such that trend data can be ascertained to better inform future management action. The diversity of non‐invasive monitoring methods now available makes such monitoring possible with relatively minor commitments of funding and effort.

Revalidation and expanded description of Mustela aistoodonnivalis (Mustelidae: Carnivora) based on a multigene phylogeny and morphology.

The lacked-teeth pygmy weasel, Mustela aistoodonnivalis Wu & Kao, 1991, was originally described as being from Taibai Mountain and Zhashui county, Shaanxi, China. Subsequently, it was considered a subspecies or synonym of Mustela nivalis. In a faunal survey of northwestern Sichuan, eight specimens of M. aistoodonnivalis were collected. A molecular phylogenetic analysis of one mitochondrial and six nuclear genes clustered the specimens as a distinct clade and not with M. nivalis. Morphologically, the lack of the second lower molar differentiated them from M. nivalis, and genetic distances were typical of discrete species. These analyses confirmed that M. aistoodonnivalis is an independent species in the genus Mustela.

A new threat for the rarest neotropical carnivore: the vulnerable Colombian weasel, Neogale felipei

Abstract The Colombian weasel, Neogale felipei, previously included in the genus Mustela, is considered the rarest carnivore in the Neotropics and is known from only eight localities in Colombia and Ecuador. It is currently classified as Vulnerable, but little is known about the direct threats that the species faces. We present a new locality record for N. felipei in the Andes of southwestern Colombia based on a road-killed specimen. The record is relevant because it provides additional information about morphological variation and describe a new threat to its populations that even affects individuals within protected areas such as the Puracé National Park, where the specimen was found.

Complete mitochondrial genome of the least weasel Mustela nivalis (Mustelidae) in Korea

The complete mitogenome (MF459691) of Mustela nivalis contains total 16,502 bp in length and consists of a control region and a conserved set of 37 genes. The phylogenetic tree of the family Mustelidae constructed using 18 mitogenome sequences from 16 mustelid species of 6 genera shows that the mustelid species are separated into two main groups. All the members of the genus Martes form a monophyletic group, which has the genus Melogale as sister clade, and the clade of the two genera is sister to that of the genera Enhydra and Lutra. Among species of the genus Mustela, with the exclusion of M. frenata with Neovison vison as sister species, all the other species of the genus Mustela are well grouped. All members of M. nivalis are well placed within the species M. nivalis clade with the clade of M. itatsi and M. sibirica as sister group.

First report of Filaria martis Gmelin, 1790 in the European mink, Mustela lutreola (Linnaeus, 1761).

The riparian European mink (Mustela lutreola), currently surviving in only three unconnected sites in Europe, is now listed as a critically endangered species according to the IUCN. Habitat loss and degradation, anthropic mortality, interaction with the feral American mink (Neovison vison), and infectious diseases are among the principal causes of its decline. Surveys of helminth parasites of this host that also include focus on subcutaneous potentially pathogenic helminths such as those belonging to the genus Filaria are very scarce. We report here the presence of specimens of Filaria martis in the subcutaneous connective tissues of three M. lutreola individuals from Spain. This is the first finding of a subcutaneous nematode in a representative of the genus Mustela. The report also enlarges the known range of the definitive hosts of this nematode. These worms were mainly located in the dorsal region of mink and more rarely in the knees, elbows, and hips. Skin sloughing was only observed in one M. lutreola with both septicaemia and an associated high burden of F. martis. Therefore, more attention should be paid to potentially pathogenic helminths when designing conservation programs dedicated to M. lutreola.

Influence of predation risk on recruitment and litter intervals in common voles (Microtus arvalis)

Research on mammals and birds has shown that predation may have indirect effects on prey reproduction. Some of the indirect effects may give prey an adaptive advantage. Females of several vole species respond to the presence of predators from the genus Mustela L., 1758 with suppressed breeding; this response increases females’ chances of survival. However, breeding suppression is observed only in a certain part of the female population; it is unclear whether predation risk affects the remaining females. We investigated this in a capture–mark–recapture experiment on reproductive effort of female common voles (Microtus arvalis (Pallas, 1778)) facing simulated presence of mustelid predators. We measured two parameters: the number of recruits per litter and the litter interval. Compared with control populations, the number of recruits per litter was not affected, but the litter interval was longer in females facing mustelid risk of predation. This indicates that predation risk affects females in a more complex way than originally proposed: it induces breeding suppression in some, but also influences litter frequency in others. Our result suggests that predatory stress deregulates the estrous cycle. Decreased frequency of litters can be a viable antipredatory adaptation in iteroparous organisms.

Integrative study on static skull variation in the Japanese weasel (Carnivora: Mustelidae)

AbstractWe assessed static skull variation in the Japanese weasel Mustela itatsi by integrating different variation indices. We used the coefficient of variation (CV), residuals of the standard deviation regressed onto the mean of each measurement (RSD) and allometry coefficients (ACs). CV showed nonlinear correlation with mean trait size as reported in many previous studies. RSD has a similar pattern of variation to CV and it has been used as an index to obliterate the trait size bias seen in CV. Furthermore, similarly sized traits showed a wide range of CV, with many largely scattered around a nonlinear regression curve. Therefore, variation in CV is not entirely generated by the bias and to some extent reflects real biological phenomena. Allometric analyses revealed that larger specimens tended to have a relatively larger viscerocranium, smaller neurocranium, more robust mandible, larger canines, smaller carnassials, and smaller M1 compared with smaller specimens. These patterns are possibly consistent with general ontogenetic skull shape change in the genus Mustela. Tooth measurements, as well as cranial and mandibular measurements, showed significant correlations with skull size. CV variation is determined mainly by AC and is weakly related to the correlation between trait and skull size.

New Insights into the Evolution of Intronic Sequences of the β-fibrinogen Gene and Their Application in Reconstructing Mustelid Phylogeny

Mustelidae is the largest and most diverse family in the order Carnivora. The phylogenetic relationships among the subfamilies have especially long been a focus of study. Herein we are among the first to employ two new introns (4 and 7) of the nuclear beta-fibrinogen gene to clarify these enigmatic problems. In addition, two previously available nuclear (IRBP exon 1 and TTR intron 1) and one mt (ND2) data sets were also combined and analyzed simultaneously with the newly obtained sequence data in this study. Detailed characterizations of the two intronic regions not only reveal the remarkable occurrences of short interspersed element (SINE) insertion events, providing a new example supporting the attractive hypothesis that attrition of an earlier retroposition may offer a proper environment for successive retropositions by forming a "dimer-like" structure, but also demonstrate their utility in the resolution of mustelid phylogeny. All of our analyses confirm the assemblage of Mustelinae, Lutrinae, and Melinae with confidence; moreover, two clades within Mustelinae were clearly recognized, i.e., genera Mustela and Martes. Notably, genus Martes of Mustelinae was found to branch off first, followed by Melinae and then a clade containing Lutrinae and genus Mustela of Mustelinae, indicating paraphyly of Mustelinae. In addition, Mephitinae diverges before the other mustelids and the monophyletic Procyonidae in all cases, supporting its elevation to a separate family. Additional independent genetic markers are still in need to resolve the trichotomy among Mephitinae and the other two carnivoran clades, Ailuridae and Procyonidae/non-mephitine Mustelidae.

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

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 species of Mustela, including the domestic ferret and the American mink. 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 Japanese weasel (Mustela itatsi) formerly classified as a subspecies of the Siberian weasel (M. sibirica), was genetically well-differentiated from M. sibirica, and the two species clustered with each other. The European mink (M. lutreola) was closely related to “the ferret group” (M. furo, M. putorius, and M. eversmanii). Both the American mink of North America and the back-striped weasel (M. strigidorsa) of Southeast Asia 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 weasels. 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, Neovison.

Dental Divergence Supports Species Status of the Extinct Sea Mink (Carnivora: Mustelidae:Neovison macrodon)

The sea mink (Neovison macrodon (Prentiss, 1903): Mustelinae) was an unusual late-Cenozoic example of an organism that had rapidly evolved toward a marine niche. Except for the otters, it was probably the most aquatic member of the Musteloidea. Its status as a separate species has not been resolved. A larger relative of the American mink (N. vison), it inhabited the shores of New England and possibly the Canadian Maritime Provinces until it was hunted to extinction in the 19th century. Skeletal and skin specimens were not collected by zoologists, but the former are known from Native American archaeological sites. The hypothesis that the sea mink showed dental divergence from N. vison, an indication of systematic and ecological distinctness, was tested on 111 dentally mature mink specimens originally collected from the Turner Farm archaeological site (Penobscot Bay, Maine). These teeth, dating from about 5,000 to 250 years ago, were compared with 158 other specimens measured for this study and published data from 78 individuals, representing 4 subspecies of N. vison and 22 additional musteloid genera. Thirteen dental measurements were taken on all species and studied using regressions, principal component analysis, and significance testing. Based on comparisons with American mink, it appears likely that the archaeological specimens included primarily N. macrodon but also N. vison. Although pairs of species within the Lutrinae and genus Mustela showed divergence comparable to that of N. vison and N. macrodon, the dental proportions of male and female N. vison and of the several N. vison subspecies were nearly identical. These analyses suggest that N. macrodon was sufficiently distinct from N. vison to support its recognition as a separate species.

Role of fruits in the diet of small mustelids (Mustela sp.) from the western Italian Alps

The food habits of both weasels and stoats (Mustela nivalis and M. erminea) and the occurrence of fruit in their diet were studied by scat analysis in the Gran Paradiso National Park (western Italian Alps). Being impossible to distinguish between stoats and weasels scats, they were grouped together as the genus Mustela. Despite the high consumption of small rodents, which represented the main food item in the diet of small mustelids (41.5% in mean volume), wild fruits (mainly Rosaceae and Ericaceae) were also relatively common (23.3% in mean volume). Fruits were exploited throughout the year, with an intensive use in seasons of high availability. Their consumption did not significantly differ between habitat types, despite a significant decrease of fruit availability from deciduous mixed forest to alpine prairie. This evidence suggests that this trophic behaviour could represent a consolidated feeding strategy of both weasels and stoats, which seem to adopt an opportunistic behaviour as shown by larger size mustelids. We argue that fruits, owing to their good availability and high profitability, could play an important role in the diet of small mustelids in alpine habitats, slackening their well-documented dependence on rodents.

Intrageneric Diversity of the CytochromebGene and Phylogeny of Eurasian Species of the Genus Mustela (Mustelidae, Carnivora)

To illuminate molecular phylogenetic relationships among Eurasian species of the genus Mustela (Mustelidae, Carnivora), we determined nucleotide sequences of the complete mitochondrial cytochrome b gene region (1,140 base pairs). Molecular phylogenetic trees, constructed using the neighbor-joining and the maximum likelihood methods, showed the common topology of species relationships to each other. The American mink M. vison first branched off and was positioned very remotely from the other species of Mustela. Excluding M. vison, the ermine M. erminea first split from the rest of the species. Two small body-sized weasels, the least weasel M. nivalis and the mountain weasel M. altaica, comprised one cluster (named "the small weasel group"). The other species formed another cluster, where the remarkably close relationships among the domestic ferret M. furo, the European polecat M. putorius, and the steppe polecat M. eversmanni were noticed with 87-94% bootstrap values (named "the ferret group"), supporting the history that the ferret was domesticated from M. putorius and/or M. eversmanni. The European mink M. lutreola was the closest to the ferret group. The genetic distance between the Siberian weasel M. sibirica and the Japanese weasel M. itatsi corresponded to differences of interspecific level, while the two species were relatively close to M. lutreola and the ferret group. These results provide invaluable insight for understanding the evolution of Mustela as well as for investigating the hybridization status between native and introduced species for conservation.

Phylogeographic Variation in Two Mustelines, the Least Weasel Mustela nivalis and the Ermine M. erminea of Japan, Based on Mitochondrial DNA Control Region Sequences

Abstract The least weasel Mustela nivalis and the ermine M. erminea of Japan are considered relicts of the last glacial period. To study phylogeographic variation in these mustelines, fragments of the mitochondrial DNA control region were sequenced. In both species, the control region included tandem repeats of 10base motifs at the 3′ portion specific to the genus Mustela. Phylogenetic trees of the 5′ portion (581–584 bases) of M. nivalis indicated that haplotypes in the Hokkaido population clearly diverged from those in the Honshu population. Geographic pattern of intraspecific variations illustrated by this result is concordant with that by the result of a previous cytogenetic study, which revealed the karyotypic differentiation between the two populations. These findings might suggest that the Hokkaido and Honshu populations of M. nivalis were geographically isolated in advance of the formation of the Tsugaru strait between Hokkaido and Honshu. Distribution pattern of the mitochondrial DNA haplotypes w...

Phylogenetic relationships of otters (Carnivora: Mustelidae) based on mitochondrial cytochrome b sequences

Otters are classified in the Lutrinae and are united by a suite of semi-aquatic adaptations that distinguish them from the rest of the Mustelidae. Past systematic studies have been based primarily on overall similarity of morphological characters but have not been concordant, with regard either to relationships within the subfamily or to the relationships of the Lutrinae to other taxa in the Mustelidae. We evaluate the relationships among nine of the 13 species of otters and their position in the Mustelidae through phylogenetic analysis of the complete nucleotide sequence of the mitochondrial cytochrome b gene. Based on the sequence data presented here, our results suggest that otters are divided into three primary clades that include: (1) the North American river, neotropical and marine otters; (2) the sea, Eurasian, spotted-necked, cape clawless and small-clawed otters; and (3) the giant otter. Furthermore, our results indicate that among sampled mustelid taxa, members of the genus Mustela are most closely related to otters. The hierarchical relationships among clades are not well resolved, particularly the monophyly of otters, largely because a pattern of short internal branches combined with long terminal branches suggests a rapid evolutionary radiation. Estimates of divergence time calibrated by the fossil record suggest that the lineages leading to the North American river, neotropical and marine otters, and the giant otter diverged before the end of the Miocene, much earlier than predicted from the fossil record.

Phylogenetic relationships of otters (Carnivora: Mustelidae) based on mitochondrial cytochrome b sequences

AbstractOtters are classified in the Lutrinae and are united by a suite of semi‐aquatic adaptations that distinguish them from the rest of the Mustelidae. Past systematic studies have been based primarily on overall similarity of morphological characters but have not been concordant, with regard either to relationships within the subfamily or to the relationships of the Lutrinae to other taxa in the Mustelidae. We evaluate the relationships among nine of the 13 species of otters and their position in the Mustelidae through phylogenetic analysis of the complete nucleotide sequence of the mitochondrial cytochrome b gene. Based on the sequence data presented here, our results suggest that otters are divided into three primary clades that include: (1) the North American river, neotropical and marine otters; (2) the sea, Eurasian, spotted‐necked, cape clawless and small‐clawed otters; and (3) the giant otter. Furthermore, our results indicate that among sampled mustelid taxa, members of the genus Mustela are most closely related to otters. The hierarchical relationships among clades are not well resolved, particularly the monophyly of otters, largely because a pattern of short internal branches combined with long terminal branches suggests a rapid evolutionary radiation. Estimates of divergence time calibrated by the fossil record suggest that the lineages leading to the North American river, neotropical and marine otters, and the giant otter diverged before the end of the Miocene, much earlier than predicted from the fossil record.

Distribution of cardiac musculature in the pulmonary venous wall of three species of the genus Mustela.

An examination was made of the distribution of cardiac musculature in the pulmonary venous wall of three Mustela species (ermine, American mink and ferret) of different body size. Only the ermine possessed cardiac myocytes in the tunica media of the intrapulmonary venous walls continuing from the left atrium, whereas the two other species had the musculature restricted to the large extrapulmonary vein. The distribution of the musculature is thought to depend on the body weight and heart rate of various species. These findings confirm the supposition that, whereas smaller mammals have more extensive cardiac musculature, even in the intrapulmonary venous wall, in order to regulate venous blood return and to resist reflux resulting from frequent atrial systole, the larger species may not require cardiac musculature in the distal vein.

Genus Mustela

Genus Mustela