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Superior and lateral views of an Arctic fox cranium showing the measurements taken for this study. CBL, overall condylobasal length; RL, absolute rostrum length; BL, braincase length; NASL, nasal bone length; BRCW, maximum braincase width; PORW, postorbital width; BRCH, braincase height.
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Arctic foxes, Vulpes lagopus living on Mednyi Island suffered a drastic decline in population size in the late 1970s due to an outbreak of mange epizootic. This dramatic fall in numbers rendered the subspecies endangered, and the concomitant loss of variability resulted in a population bottleneck. Here, we investigate whether differences in cranial...
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... are housed in the Zoological Museum of M.V. Lomonosov Moscow State University, and were collected in the wild on Mednyi Island before the bottleneck event (29 specimens, including 16 males, 10 females and three of unknown sex) and after it (24 specimens, including nine males, six females and nine of unknown sex), and on Bering Island before (32 specimens, including 17 males and 15 females) and after (32 specimens, including 15 males and 17 females). Seven linear measurements of the cranium (Figure 1; raw data provided as supplementary information, Table S1) were taken with a Sylvac digital calliper (Sylvac, Crissier, Switzerland) to an accuracy of 0.1 mm. The measurements are defined as follows: overall condylobasal length (CBL), defined as the distance between the base of incisors at the midline and the posterior curve of the condyles; absolute rostrum length (RL), defined as the distance between base of incisors at the midline and ectorbitale; braincase length (BL), defined as the ectorbitale-akrokranion distance; nasal bone length (NASL), defined as the maximum length of the nasal bone along the lateral edge; maximum braincase width (BRCW), defined as the maximum width of the cranium at the parietal bones; postorbital width (PORW), defined as the width of the cranium at the postorbital constriction; braincase height (BRCH), defined as the distance between the maximum bend of parietal bones (excluding the sagittal crest) and the base of the cranium between the condyles. ...
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Citations
... It is well documented that isolation and/or large demographic declines affect the ability of a population to maintain genetic diversity over time due to genetic drift (Frankham, 1997;Keller and Waller, 2002). Genetic studies have shown that the current Mednyi population indeed displays low variability (Ploshnitsa et al., 2012;Prôa and Nanova, 2020), a probable consequence of the bottleneck in the 1970s (Ploshnitsa et al., 2012) or of being isolated for such a long period. In this context, a reduction in the diversity of the major histocompatibility complex (MHC), an important genetic system for combatting infections in vertebrates (e.g. ...
... In some cases, the two populations of Arctic foxes of the Commander Islands are considered as a single subspecies (for example, Wozencraft, 2005;Sillero-Zubiri, 2009), which is wrong because of great genetic (Geffen et al., 2007) and morphological (Martin-Serra et al., 2019) differences between the Arctic foxes of Mednyi Island and Bering Island. In addition, each of these isolated populations has its own unique history (Goltsman et al., 1996;Ryazanov, 2002;Shienok et al., 2017;Prôa and Nanova, 2020). ...
... The skull of the Arctic fox of the Commander Islands (especially of the Arctic fox from Mednyi Island) is more stress-resistant and allows greater bite force and more efficient prey holding and butchering (Nanova et al., 2017). The population bottlenecks of Arctic foxes of the Commander Islands, characteristic of island populations, could effectively fix the results of selection, thereby accelerating the evolution on the islands (Prôa and Nanova, 2020). The increase in the size of the Arctic fox of the Commander Islands can also be associated with the feeding on larger prey. ...
The Arctic foxes, Vulpes lagopus, from the Commander Islands are known to be well differentiated in skull morphology from the mainland population. Our study is the first to compare this differentiation with interspecies variations in the family Canidae. The level of skull variations between the Arctic foxes of the Commander Islands and the mainland Arctic fox was compared with skull variations between (1) the gray fox, Urocyon cinereoargenteus, and the island fox, U. littoralis; and (2) three closely related species of the Arctic fox: the swift fox, V. velox, and the kit fox, V. macrotis. The skull variations between the Arctic foxes of the Commander Islands and the mainland Arctic fox were shown to correspond to the interspecies level of skull variation in sister species of the genera Vulpes and Urocyon. No general trend in skull variation has been found between the species studied and isolated populations. The craniological data presented support the separation of foxes from the Commander Islands as a distinct species, V. beringensis Merriam 1902, with two subspecies: V. b. semenovi Ognev 1931 (Medny Island) and V. b. beringensis Merriam 1902 (Bering Island). The Arctic foxes of the Commander Islands are a unique part of the biological diversity and must be strictly protected.
... Studying the morphological variability of recent V. vulpes and V. lagopus from Northern Eurasia, we found significant differentiation in the dental characters between mainland V. lagopus and Commander Islands V. lagopus (Gimranov, 2014). The presence of such differentiation in V. lagopus (exterior, dimensional, and genetic) has been frequently discussed by researchers (Heptner et al., 1967;Džikija et al., 2007;Geffen et al., 2007;Szuma, 2008Szuma, , 2011Ploshnitsa et al., 2012Ploshnitsa et al., , 2013Martín-Serra et al., 2019a;Proa & Nanova, 2019). The reasons for these differences are clearly related to the island specificity of these animals and their isolation from the mainland community. ...
... The dentition of the island groups represents a mixture of primitive, advanced, and unique features. One explanation for this phenomenon is the possible bottleneck event that might have taken place either as a result of long-term isolation on the islands or during the initial settlement of the islands at the turn of the Holocene (Goltsman et al., 2005;Džikija, 2008;Proa & Nanova, 2019). Another potential factor that could have led to a change in dentition might be the narrow range of food resources available on the islands. ...
... генетические (Geffen et al., 2007) и морфологические (Martin-Serra et al., 2019) различия между песцами о-в Медный и о-в Беринга велики. Кроме того, каждая из этих изолированных популяций обладает своей уникальной историей (Рязанов, 2002;Goltsman et al., 1996;Shienok et al., 2017;Prôa, Nanova, 2020). ...
... Во-первых, при изъятии размера из данных изменчивость становится значительно менее структурированной. Так, со включенным размером 90% общей изменчивости (Prôa, Nanova, 2020). Увеличение размеров командорских песцов также может быть связано с питанием более крупной добычей. ...
The Arctic foxes, Vulpes lagopus, from the Commander Islands are known to be well differentiated in skull morphology from the mainland population. Our study is the first to compare this differentiation with interspecific variations in the family Canidae. The level of skull variation between the Commander Islands’ Arctic foxes and the mainland arctic fox was compared with: (1) skull variations between the Grey fox, Urocyon cinereoargenteus, and the Island fox, U. littoralis; and (2) skull variations between three closely related species the Arctic fox; the Swift fox, V. velox, and the Kit fox, V. macrotis. The present study shows that skull variations between the Commander Islands’ Arctic foxes and the mainland Arctic fox correspond to the interspecific level of skull variation in sister species of the genera Vulpes and Urocyon. No general trend in skull variation
has been found between the studied species and isolated populations. The presented craniological data support the separation of the Commander Islands’ foxes as a distinct species, V. beringensis Merriam 1902, with two subspecies involved: V. b. semenovi Ognev 1931 (Mednyi Island) and V. b. beringensis Merriam 1902 (Bering Island). The Commander Islands’ Arctic foxes are a unique part of biological diversity and must be strictly protected.
... Беринга велики. Кроме того, каждая из этих изолированных популяций обладает своей уникальной историей (Рязанов, 2002;Goltsman et al., 1996;Shienok et al., 2017;Prôa, Nanova, 2020). ...
... Медный) более устойчив к нагрузкам, позволяет развивать большую силу укуса и эффективнее удерживать и разделывать добычу . Прохождение командорских песцов через бутылочные горлышки численности, характерные для островных популяций, могли эффективно фиксировать результаты отбора, тем самым ускоряя темпы эволюции на островах (Prôa, Nanova, 2020). ...
The Commander Island arctic foxes Vulpes lagopus are well differentiated in skull morphology from the mainland arctic fox. This differentiation was compared with interspecific variation in Canidae family in our study for the first time. The level of skull variation between the Commander Islands arctic foxes and the mainland arctic foxes was compared with: 1) skull variation between gray fox Urocyon cinereoargenteus and island fox U. littoralis; 2) skull variation between three close species the arctic fox, swift fox V. velox, and kit fox V. macrotis. Results of the present study show that skull variation between the Commander Islands arctic foxes and mainland arctic foxes corresponds to interspecific level of skull variation in sister species of Vulpes and Urocyon genera. We did not find a general trend in skull variation between studied species and isolated populations. Presented craniological data support the separation of the Commander Islands foxes by Ognev, 1931 as distinct species V. beringensis Merriam, 1902 with two subspecies V.b. semenovi Ognev, 1931 (Mednyi Island) and V. b. beringensis Merriam, 1902 (Bering Island). The Commander Islands arctic foxes are unique part of biological diversity and must be strictly protected.
Key words: Commander Islands, island isolation, arctic fox, island fox, cranium, Vulpes, Urocyon
... Vertebrate cranial form Miguel Prôa 53 "The results showed that differences in cranial morphology between the Mednyi population and the Bering population after the 1970s could be attributed to the population bottleneck caused by an outbreak of mange epizootic." (Prôa & Nanova 2019) ...
... "The results showed that differences in cranial morphology between the Mednyi population and the Bering population after the 1970s could be attributed to the population bottleneck caused by an outbreak of mange epizootic."(Prôa & Nanova 2019) Could high mortality have created a bottleneck effect, where alleles were lost at random, affecting cranial morphology?"The results showed that differences in cranial morphology between the Mednyi population and the Bering population after the 1970s could be attributed to the population bottleneck caused by an outbreak of mange epizooti ...
Durante el Pleistoceno, América del Sur tenía varios géneros y especies de grandes cánidos hipercarnívoros, los cuales se extinguieron completamente al final de esta época. En este trabajo se presenta una revisión sistemática exhaustiva del grupo (cuatro géneros y siete especies), sobre la base de nuevos análisis cladísticos que también contemplan información genómica y un estudio de la variación intraespecífica en cánidos. Se discuten los resultados generados sobre la filogenia, sistemática, bioestratigrafía y biogeografía de los cánidos sudamericanos. Se sinonimizó Protocyon orcesi con Protocyon troglodytes y Canis nehringi con Aenocyon dirus. El género Theriodictis sería parafilético por lo que Theriodictis tarijensis fue transferido a Protocyon. “Canis” gezi claramente no pertenece al género Canis. Las distribuciones de A. dirus y P. troglodytes llegarían hasta la región pampeana y México, respectivamente. Por otro lado, se restringió a la región pampeana la distribución de Theriodictis. El carácter fragmentario de varios taxones de América del Norte y del Sur complican su ubicación filogenética y las interpretaciones biogeográficas y evolutivas, pero se pueden inferir varios eventos inmigratorios desde América del Norte y Central y algunos posteriores en sentido contrario, así como también una diversificación importante dentro de América del Sur. Nuevos ejemplares bien preservados son necesarios para evaluar la presencia de Chrysocyon y Theriodictis fuera de América del Sur y la asignación sistemática de los restos de cánidos de los sitios de Orocual (Venezuela). La evidencia disponible no permite corroborar la presencia de grandes cánidos con anterioridad al Ensenadense (>1,8 Ma).
Phenotypic integration and modularity influence morphological disparity and evolvability. However, studies addressing how morphological integration and modularity change for long periods of genetic isolation are scarce. Here, we investigate patterns of phenotypic integration and modularity in the skull of phenotypically and genetically distinct populations of the Artic fox (Vulpes lagopus) from the Commander Islands of the Aleutian belt (i.e. Bering and Mednyi) that were isolated ca 10 000 years by ice-free waters of the Bering sea. We use three-dimensional geometric morphometrics to quantify the strength of modularity and integration from inter-individual variation (static) and from fluctuating asymmetry (random developmental variation) in both island populations compared to the mainland population (i.e. Chukotka) and we investigated how changes in morphological integration and modularity affect disparity and the directionality of trait divergence. Our results indicate a decrease in morphological integration concomitant to an increase in disparity at a developmental level, from mainland to the smallest and farthest population of Mednyi. However, phenotypic integration is higher in both island populations accompanied by a reduction in disparity compared to the population of mainland at a static level. This higher integration may have favoured morphological adaptive changes towards specific feeding behaviours related to the extreme environmental settings of islands. Our study demonstrates how shifts in phenotypic integration and modularity can facilitate phenotypic evolvability at the intraspecific level that may lead to lineage divergence at macroevolutioanry scales.
