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Arvicolinae is a subfamily of rodents that includes the voles, lemmings, and muskrats. Its closest relatives are members of the other subfamilies in the Cricetidae, the hamsters and New World rats and mice[1]. Sometimes the subfamily Arvicolinae is placed in the family Muridae along with all other members of the superfamily Muroidea [2]. It is also sometimes referred to as Microtinae or is recognized as a family, Arvicolidae [3].
[edit] DescriptionThe arvicolines are most easily identified based on their molar teeth, which show prismatic cusps consisting of alternating triangles. These molars are ever-growing and are well adapted to a herbivorous lifestyle. Arvicolines are Holarctic in distribution and represent one of the only major muroid radiations to reach the New World via Beringia. The other are the three subfamilies of New World rats and mice. Arvicolines do very well in the subnival zone beneath the winter snowpack and persist throughout winter without needing to hibernate. They are also characterized by extreme fluctuations in population size. Most arvicolines are small, furry, short tailed voles or lemmings, but some such as Ellobius and Hyperacrius are well adapted to a fossorial lifestyle. Others, such as Ondatra, Neofiber, and Arvicola have evolved a larger body size and associated with an aquatic lifestyle. Some authorities have placed the zokors within the Arvicolinae, but they have been shown to be unrelated. The subfamily Arvicolinae contains ten tribes, seven of which are classified as voles, one as lemmings, and two as muskrats. [edit] Classification Skull of a Bank Vole. Note the distinctive molar pattern characteristic of arvicolines.
[edit] Fossil species
[edit] PhylogenyThe phylogeny of Arvicolinae has been studied using morphological and molecular characters. Markers for the molecular phylogeny of arvicolines included the mitochondrial DNA cytochrome b (cyb) gene [4] and the exon 10 of the growth hormone receptor (ghr) nuclear gene [5]. The comparison of the cyb and ghr phylogenetic results seems to indicate that nuclear genes are useful for resolving relationships of recently evolved animals. As compared to mitochondrial genes, nuclear genes display several informative sites in third codon positions that evolve rapidly enough to accumulate synapomorphies, but slow enough to avoid evolutionary noise. Of note, mitochondrial pseudogenes translocated within the nuclear genome complicate the assessment of the mitochondrial DNA orthology, but they can also be used as phylogenetic markers [6]. Sequencing complete mitochondrial genomes of voles [7] may help to distinguish between authentical genes and pseudogenes. The complementary phylogenetic analysis of morphological and molecular characters [5][8] suggests that :
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[edit] External links
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