Comparative Genomics of Mitochondrial DNA in Drosophila simulans

The current study compares the nucleotide variation among 22 complete mitochondrial genomes of the three distinct Drosophila simulans haplotypes with intron 1 of the alcohol dehydrogenase-related locus. This is the first study to investigate the sequence variation of multiple complete mitochondrial genomes within distinct mitochondrial haplotypes of a single species. Patterns of variation suggest distinct forces are influencing the evolution of mitochondrial DNA (mtDNA) and autosomal DNA in D. simulans. First, there is little variation within each mtDNA haplotype but strong differentiation among them. In contrast, there is no support for differentiation of the mitochondrial haplotypes at the autosomal locus. Second, there is a significant deficiency of mitochondrial variation in each haplotype relative to the autosomal locus. Third, the ratio of nonsynonymous to synonymous substitutions is not equal in all branches of the well-resolved phylogeny. There is an excess of nonsynonymous substitutions relative to synonymous substitutions within each D. simulans haplotype. This result is similar to that previously observed within the mtDNA of distinct species. A single evolutionary force may be causally linked to the observed patterns of mtDNA variation—a rickettsia-like microorganism, Wolbachia pipientis, which is known to directly influence mitochondrial evolution but have a less direct influence on autosomal loci. Received: 16 September 1999 / Accepted: 14 March 2000     

Mitochondrial DNA and microsatellite DNA variation in domestic reindeer (Rangifer tarandus tarandus) and relationships with wild caribou (Rangifer tarandus granti, Rangifer tarandus groenlandicus, and Rangifer tarandus caribou)

Reindeer (Rangifer tarandus tarandus) in Alaska are semidomestic livestock descended from 1280 animals introduced from Siberia, Russia, approximately 100 years ago. Genetic variation at 18 microsatellite DNA loci and the cytochrome b gene of mitochondrial DNA (mtDNA) was quantified in reindeer from Alaska, Siberia (Russia), and Scandinavia and compared with wild North American caribou. Mean sequence divergence among 15 mtDNA haplotypes in reindeer was 0.007 substitutions per nucleotide site, and reindeer mtDNA is polyphyletic with caribou mtDNA. Microsatellite allele and mtDNA haplotype frequencies are similar between Alaskan and Russian reindeer and differentiated between these and Scandinavian reindeer. The frequencies of microsatellite alleles and mtDNA haplotypes are different in reindeer and wild caribou (Rangifer tarandus granti, Rangifer tarandus groenlandicus, and Rangifer tarandus caribou). Alaskan reindeer have maintained a genetic variation comparable to that in Russia and differentiated from that of wild caribou, >100 years after their introduction to Alaska.     

MITOCHONDRIAL DNA VARIABILITY OF STRIPED DOLPHINS (STENELLA COERULEOALBA) IN THE SPANISH MEDITERRANEAN WATERS

Frozen muscle samples from 44 striped dolphins stranded on the Spanish Mediterranean coasts from 1990 to 1993 have been studied by means of mitochondrial DNA (mtDNA) restriction site analysis. Thirty-five of these dolphins were affected by a die-off occurring during this time in the western Mediterranean Sea. The mtDNA from each dolphin was digested with 15 restriction endonucleases that recognized 61 different restriction sites. The specific location of these sites on the mitochondrial gene map allowed us to determine the distribution of variability along this molecule. From the restriction analysis, a total of 15 different composite patterns or haplotypes was obtained and their phylogenetic relationships established both by cladistic and phenetic methods.
Estimates of sequence divergence among the 15 haplotypes ranged from 0.148% to 0.919%. Haplotype diversity (average heterozygosity) obtained was 0.789, a high value compared to other available data on cetaceans, especially considering that only a small area of the distribution of the species has been sampled. Neither population subdivision nor any evidence of correlation between haplotype frequencies and temporal or geographic distribution of dolphins has been detected.     

Genetic structure among continental and island populations of gyrfalcons

Little is known about the possible influence that past glacial events have had on the phylogeography and population structure of avian predators in the Arctic and sub-Arctic. In this study, we use microsatellite and mitochondrial control region DNA variation to investigate the population genetic structure of gyrfalcons (Falco rusticolus) throughout a large portion of their circumpolar distribution. In most locations sampled, the mtDNA data revealed little geographic structure; however, five out of eight mtDNA haplotypes were unique to a particular geographic area (Greenland, Iceland, or Alaska) and the Iceland population differed from others based on haplotype frequency differences (F(ST)). With the microsatellite results, significant population structure (F(ST), principal components analysis, and cluster analysis) was observed identifying Greenland and Iceland as separate populations, while Norway, Alaska and Canada were identified as a single population consistent with contemporary gene flow across Russia. Within Greenland, differing levels of gene flow between western and eastern sampling locations was indicated with apparent asymmetric dispersal in western Greenland from north to south. This dispersal bias is in agreement with the distribution of plumage colour variants with white gyrfalcons in much higher proportion in northern Greenland. Lastly, because the mtDNA control region sequence differed by only one to four nucleotides from a common haplotype among all gyrfalcons, we infer that the observed microsatellite population genetic structure has developed since the last glacial maximum. This conclusion is further supported by our finding that a closely related species, the saker falcon (Falco cherrug), has greater genetic heterogeneity, including mtDNA haplotypes differing by 1-16 nucleotide substitutions from a common gyrfalcon haplotype. This is consistent with gyrfalcons having expanded rapidly from a single glacial-age refugium to their current circumpolar distribution. Additional sampling of gyrfalcons from Fennoscandia and Russia throughout Siberia is necessary to test putative gene flow between Norway and Alaska and Canada as suggested by this study.     

Association between chloroplast DNA and mitochondrial DNA haplotypes in Prunus spinosa L. (Rosaceae) populations across Europe

Chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) were studied in 24 populations of Prunus spinosa sampled across Europe. The cpDNA and mtDNA fragments were amplified using universal primers and subsequently digested with restriction enzymes to obtain the polymorphisms. Combinations of all the polymorphisms resulted in 33 cpDNA haplotypes and two mtDNA haplotypes. Strict association between the cpDNA haplotypes and the mtDNA haplotypes was detected in most cases, indicating conjoint inheritance of the two genomes. The most frequent and abundant cpDNA haplotype (C20; frequency, 51 %) is always associated with the more frequent and abundant mtDNA haplotype (M1; frequency, 84 %). All but two of the cpDNA haplotypes associated with the less frequent mtDNA haplotype (M2) are private haplotypes. These private haplotypes are phylogenetically related but geographically unrelated. They form a separate cluster on the minimum-length spanning tree.     

Bumblebee commercialization will cause worldwide migration of parasitic mites

We investigated natural populations of three Japanese native bumblebee species to determine the status of infestation by a tracheal mite, Locustacarus buchneri, which we had earlier detected in introduced commercial colonies of the European bumblebee, Bombus terrestris. We also investigated mite infestation in commercial colonies of a Japanese native species, B. ignitus, which are mass-produced in the Netherlands and reimported into Japan. We detected the mite in both natural and commercial colonies of the Japanese species. Comparison of 555 bp sequences of the mitochondrial DNA (mtDNA) cytochrome oxidase 1 (CO1) gene from the mite showed that there were seven haplotypes, on the basis of combinations of substitutions at eight sites in the gene. The haplotypes of the mites in the Japanese native bumblebees and the haplotypes of the mites in B. terrestris did not overlap; however, mtDNA of mites detected in the commercial colonies of B. ignitus possessed the same sequence as a European haplotype. These results indicate that transportation of bumblebee colonies will cause overseas migration of parasitic mites of different origins.     

Discovery of a new nucleotide substitution in the MC1R gene and haplotype distribution in native and non-Japanese chicken breeds

Melanocortin 1-receptor (MC1R) is one of the major genes that controls chicken plumage colour. In this study, we investigated the sequence and haplotype distribution of the MC1R gene in native Japanese chickens, along with non-Japanese chicken breeds. In total, 732 and 155 chickens from 30 Japanese and eight non-Japanese breeds respectively were used. Three synonymous and 11 non-synonymous nucleotide substitutions were detected, resulting in 15 haplotypes (H0–H14). Of these, three were newly found haplotypes (H9, H13 and H14), of which one (H9) was composed of known substitutions C69T, T212C, G274A and G636A. The second one (H13) possessed newly found non-synonymous substitution C919G, apart from the known substitutions C69T, G178A, G274A, G636A and T637C. The third one (H14) comprised a newly discovered substitution C919G in addition to the known C69T, G274A and G409A substitutions. The homozygote for this new haplotype exhibited wt like plumage despite the presence of G274A. In addition to discovering a new nucleotide substitution (C919G) and three new haplotypes, we defined the plumage colour of the bird that was homozygous for the A644C substitution (H5 haplotype) as wheaten-like for the first time; although the substitution has been already reported, its effect was not revealed. Besides detecting the new plumage colour, we also confirmed that the A427G and G274A substitutions contribute in expressing brownish and black plumage colour respectively, as reported by the previous studies. Moreover, we confirmed that the buttercup allele does not express black plumage despite possessing a G274A substitution, under the suppression effect of A644C. In contrast, the birds homozygous for the birchen allele presented solid black plumage, which was contradictory to the previous reports. In conclusion, we revealed a large diversity in the MC1R gene of native Japanese chicken breeds, along with the discovery of a new non-synonymous nucleotide substitution (C919G) and three novel haplotypes (H9, H13 and H14).     

Cryptic introgression between murre sister species (Uria spp.) in the Pacific low Arctic: frequency, cause, and implications

As southern species undergo northward range expansions, reports of hybridization between temperate and arctic taxa are increasing, which may have important implications for the evolution, conservation, and management of arctic species. The extent of hybridization between temperate common murres (Uria aalge) and arctic thick-billed murres (U. lomvia), seabirds in the family Alcidae, has been the subject of debate. In a previous survey of variation in mitochondrial DNA (mtDNA) in common and thick-billed murres sampled from throughout the North Pacific and low Arctic, 12 of 327 common murres (~4%) were found to possess DNA sequences characteristic of thick-billed murres. In the present study, we surveyed variation in three nuclear introns in 230 common murres and 56 thick-billed murres and report that these putative hybrids carry various combinations of intron alleles from common and thick-billed murres. Analysis using the program STRUCTURE indicated that nine of these individuals possessed high proportions of thick-billed murre intron alleles, two possessed alleles in F1 and F2 proportions, and one individual possessed predominantly common murre intron alleles. We propose that the asymmetric mtDNA introgression we observed is most likely the result of mate choice at mixed colonies based on differences in male mating behaviours. Our results highlight that hybridization between thick-billed and common murres is more prevalent than previously thought, which may have important implications for the conservation and management of arctic-dwelling thick-billed murres as common murres expand northward.     

Declining trends in the majority of Greenland’s thick-billed murre (Uria lomvia) colonies 1981–2011

Large population declines were reported for the thick-billed murre (Uria lomvia) in Greenland for the period 1930s–1980s, but no national status has been published for the past 20 years. Meanwhile, the murres have gained more protection and several human-induced mortality factors have been markedly reduced. Here, we give an updated status based on the past 30 years of murre count data. The total Greenland population in 2011 was estimated to 468,300 birds (95 % CI 430,700–505,900) or around 342,000 breeding pairs, distributed within 19 colonies. This represents an overall reduction of 13 % since the mid-/late 1980s. In the same period, five colonies went extinct. Large and apparently stable colonies in Qaanaaq (Northwest Greenland) account for more than half the population (68 %), but most other colonies declined heavily, with up to 6 % p.a. in the most critical areas. So far, nothing indicates that food is a limiting factor in Greenland during the breeding season, although rather few colonies have been studied in details. In contrast, illegal hunting and disturbances during the breeding season are still a problem in Greenland, despite more restrictive hunting regulations, and may explain much of the continued population decline. In addition, recent studies from Svalbard indicate that a large-scale deterioration of the marine environment in the North Atlantic, due to oceanographic changes, may impact recruitment to some of the Greenland colonies. Murre colonies in southern Upernavik, Disko Bay, South Greenland and East Greenland are in urgent need of additional conservation initiatives to avoid further declines and local extinctions.     

Mitochondrial DNA distributions indicate colony propagation by single matri-lineages in the social spider Stegodyphus dumicola (Eresidae)

Colony-dwelling social spiders of the genus Stegodyphus are characterized by high colony turnover, within-colony mating, inbreeding and skewed sex ratios. These phenomena may purge genetic variation from the entire species gene pool. Social Stegodyphus have previously been discussed as ecologically unstable and evolutionary dead ends. We investigated the distribution and age (sequence divergence) of mitochondrial DNA variation for inferences of colony propagation, colony discreteness and maintenance of genetic variation in the social spider S. dumicola . In contrast to our expectations, we found abundant mtDNA variation, consisting of 15 haplotypes belonging to four haplotype lineages. Lineage divergence ranged between 2.75 and 6% for the gene ND1. Nearly all colonies (86%) were monomorphic and even neighbour colonies showed fixed differences. Simulations show that genetic drift in multifounder colonies cannot alone explain monomorphism within colonies. Haplotypes in polymorphic colonies and from neighbouring colonies were always genealogically similar. Monomorphism and the genealogical pattern among colonies suggest 'clonal' colony propagation involving single matrilineages. The divergence of haplotype lineages and distribution of haplotypes imply that colony turnover is not high enough to purge genetic variation in the species gene pool, and that S. dumicola as a species is old enough to question the instability (in ecological time) of a social spider.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 591–600.     

Mitochondrial DNA phylogeography of least cisco Coregonus sardinella in Alaska

This study presents the first detailed analysis of the mitochondrial DNA diversity of least cisco Coregonus sardinella in Alaska using a 678 bp segment of the control region (D‐loop) of the mitochondrial genome. Findings suggest that the history of C. sardinella in Alaska differs from that of other species of Coregonus present in the state and surrounding regions. The examined populations of C. sardinella are genetically diverse across Alaska. Sixty‐eight distinct mitochondrial haplotypes were identified among 305 individuals sampled from nine locations. The haplotype minimum spanning network and phylogeny showed a modest level of geographic segregation among haplotypes, suggesting high levels of on‐going or recent connectivity among distant populations. Observed Φ_ST values and the results of homogeneity and AMOVAs indicate incipient genetic differentiation between aggregations in three broad regional groups. Sites north of the Brooks Range formed one group, sites in the Yukon and Selawik Rivers formed a second group and sites south of the Yukon drainage formed the third group. Overall, the sequence data showed that a large proportion of mtDNA genetic variation in C. sardinella is shared across Alaska, but this variation is not homogeneously distributed across all regions and for all haplotype groups.     

Phylogeographical approaches to assessing demographic connectivity between breeding and overwintering regions in a Nearctic-Neotropical warbler (Wilsonia pusilla)

We characterized the pattern and magnitude of phylogeographical variation among breeding populations of a long-distance migratory bird, the Wilson's warbler (Wilsonia pusilla), and used this information to assess the utility of mtDNA markers for assaying demographic connectivity between breeding and overwintering regions. We found a complex pattern of population differentiation in mitochondrial DNA (mtDNA) variation among populations across the breeding range. Individuals from eastern North America were differentiated from western individuals and the eastern haplotypes formed a distinct, well-supported cluster. The more diverse western group contained haplotype clusters with significant geographical structuring, but there was also broad mixing of haplotype groups such that no haplotype groups were population specific and the predominance of rare haplotypes limited the utility of frequency-based assignment techniques. Nonetheless, the existence of geographically diagnosable eastern vs. western haplotypes enabled us to characterize the distribution of these two groups across 14 overwintering locations. Western haplotypes were present at much higher frequencies than eastern haplotypes at most overwintering sites. Application of this mtDNA-based method of linking breeding and overwintering populations on a finer geographical scale was precluded by the absence of population-specific markers and by insufficient haplotype sorting among western breeding populations. Our results suggest that because migratory species such as the Wilson's warbler likely experienced extensive gene flow among regional breeding populations, molecular markers will have the greatest utility for characterizing breeding-overwintering connectivity at a broad geographical scale.     

Genetic status of the wood stork (Mycteria americana) from the southeastern United States and the Brazilian Pantanal as revealed by mitochondrial DNA analysis

The wood stork (Mycteria americana) is a colonial wading bird that inhabits the Neotropical region from the southeastern United States (US) to northern Argentina. The species is considered to be endangered in the US due to degradation of its foraging and breeding habitat. In other parts of its range, such as in the Brazilian Pantanal region, breeding populations of this species appear to be stable. We compared the levels of genetic variability and population structuring of the US and the Pantanal breeding populations using mitochondrial DNA (mtDNA) control region sequences. Twenty-seven haplotypes were identified among 88 wood stork samples collected from eight breeding colonies in the US and eight in the Pantanal. Patterns indicative of heteroplasmy were observed in 35.3% of the mtDNA sequences that were examined. Significantly higher levels of haplotype diversity were observed in the Pantanal samples compared to those from the US, suggesting that during the last century, demographic declines or a recent evolutionary bottleneck reduced the levels of mtDNA variability of the US population. Analyses of genetic structuring revealed non-significant genetic differentiation between these regions, indicating that either the populations were only recently separated or that gene flow continues to occur at low levels. Haplotype network analysis indicated low current levels of gene flow between populations that were closely related in the past.     

Origin and history of mitochondrial DNA lineages in domestic horses

Domestic horses represent a genetic paradox: although they have the greatest number of maternal lineages (mtDNA) of all domestic species, their paternal lineages are extremely homogeneous on the Y-chromosome. In order to address their huge mtDNA variation and the origin and history of maternal lineages in domestic horses, we analyzed 1961 partial d-loop sequences from 207 ancient remains and 1754 modern horses. The sample set ranged from Alaska and North East Siberia to the Iberian Peninsula and from the Late Pleistocene to modern times. We found a panmictic Late Pleistocene horse population ranging from Alaska to the Pyrenees. Later, during the Early Holocene and the Copper Age, more or less separated sub-populations are indicated for the Eurasian steppe region and Iberia. Our data suggest multiple domestications and introgressions of females especially during the Iron Age. Although all Eurasian regions contributed to the genetic pedigree of modern breeds, most haplotypes had their roots in Eastern Europe and Siberia. We found 87 ancient haplotypes (Pleistocene to Mediaeval Times); 56 of these haplotypes were also observed in domestic horses, although thus far only 39 haplotypes have been confirmed to survive in modern breeds. Thus, at least seventeen haplotypes of early domestic horses have become extinct during the last 5,500 years. It is concluded that the large diversity of mtDNA lineages is not a product of animal breeding but, in fact, represents ancestral variability.     

Genetic evidence of extensive introgression of short-tailed ground squirrel genes in a hybridization zone of Spermophilus major and S. erythrogenys, inferred from sequencing of the mtDNA cytochrome b gene

We have completely sequenced the mtDNA cytochrome b gene of ground squirrels from the zone of overlapping ranges of Spermophilus major and S. erythrogenys in the Tobol-Ishim interfluve, which is a putative hybridization zone of these species. The results of the sequencing showed extensive introgression of mtDNA genes of the short-tailed ground squirrel S. e. brevicauda, whose haplotype had fully replaced the S. major haplotype. All of the ground squirrels from the Tobol-Ishim interfluve had a variant of the S. e. brevicauda mtDNA haplotype that was specific for this zone. On average, 119 substitutions (10.44%) were found between S. major from Ul'yanovsk oblast and S. e. brevicauda from the northern Kazakhstan, the mean genetic distance (D) between them being 0.115, which conforms to the corresponding parameters for the S. e. brevicauda-S. pygmaeus pair (122 substitutions, D = 118). Insignificant differences (seven substitutions, D = 0.043) were found between the S. major and S. pygmaeus haplotypes, which suggest that these species have similar mitochondrial haplotypes. Five to ten nucleotide substitutions (0.44--0.88%) were detected between the animals from the Tobol--Ishim interfluve and S. e. brevicauda. The mtDNA haplotype divergence D within the genus Spermophilus (ten species) for all codon positions ranged from 0.035 to 0.158. Phylogenetic reconstructions (MP, ML, and NJ trees) showed two well-differentiated clusters with high bootstrap support. However, there was different branching topology within the cluster and their species composition varied. The maximum likelihood tree, ML, differentiating the species into two subgenera, Citellus and Colobotis, most reliably reflected taxonomic relationships of the species from the genus Spermophilus, inferred from morphological and genetic biochemical data. The morphologically pure S. major (subgenus Colobotis) animals, used in the analysis, proved to carry the haplotype of another species, S. pygmaeus (subgenus Citellus). This poses a question on the existence of the specific haplotype of S. major, the reason of its replacement by haplotype of other species, and possible consequences of this phenomenon for survival of the species.     

藏鸡主要组织相容性复合体B-LBⅡ基因第二外显子序列遗传变异分析

根据鸡主要组织相容性复合体B-LBⅡ基因序列设计特异性引物,在藏鸡基因组中扩增了一个包括其第二外显子和第二内含子在内长度为374 bp的片段,并通过克隆和PCR直接测序获得了该片段的核苷酸序列。发现了15个B-LBⅡ新等位基因。对18个B-LBⅡ等位基因核苷酸序列和其所编码的MHCB-LBⅡ分子β1结构域的氨基酸序列分析显示,第二外显子核苷酸序列遗传多态性异常丰富,存在着62个多态变异位点(共包括80个突变),其中41个为简约性多态位点;衡量该序列遗传多样性的π值为0.0718;反映其群体内遗传变异度的平均遗传距离为0.056±0.008,低于在5个外来品种所估算的平均遗传距离。该编码区核苷酸相对异义替换率(15.61±2.69%)显著高于其同义替换率(3.25±0.94%),进一步分析表明,基因重组和平衡选择机制可能是引起B-LBⅡ基因序列变异的主要因素。在β1结构域氨基酸序列中,存在11个同义替换和27个异义替换;在24个肽结合位点中有12个变异位点;与其他6个中国地方鸡品种和一个外来品种比较发现,有11个异义氨基酸替换仅出现在藏鸡群体中,并被认为与藏鸡的免疫特异性有关,可为鸡的抗病力研究提供分子依据。     

Mitochondrial DNA variability in the Canary Islands honeybees (Apis mellifera L.)

The mitochondrial DNA (mtDNA) of individuals from 79 colonies of Apis mellifera from five Canary Islands was studied using the Dra I test based on the restriction of PCR products of the tRNAleu–COII intergenic region. Five haplotypes of the African (A) lineage and one of the west European (C) lineage were found. The haplotypes A14 and A15 are described for the first time. These haplotypes have a new P sequence named P₁. The wide distribution and high frequency of haplotype A15 suggest that it is characteristic of the Canarian Archipelago. Sources of haplotype variability of honeybee mtDNA in the Canary Islands (waves of colonization from Africa, queen importations, habitat diversification) are discussed.     

Detection of mitochondrial DNA from domestic cattle in bison on Santa Catalina Island

In 1924, 14 American bison (Bison bison) were introduced to Santa Catalina Island, California and sporadically supplemented thereafter with additional animals. To reduce the herd and its impact on native vegetation, over 2000 animals have been exported during the past four decades. Today, the herd is estimated to contain around 250 individuals. Genetic analysis was performed on 98 animals removed from the island in 2004. Forty-four samples (45%) had domestic cattle mitochondrial DNA (mtDNA), 12 (12%) had previously reported bison haplotypes and 42 (43%) had a new haplotype differing by one base pair from a previously reported bison haplotype. A complement of five restriction enzymes was found to be useful in identifying bison with domestic cattle mtDNA.     

Nonshivering thermogenesis capacity associated to mitochondrial DNA haplotypes and gender in the greater white-toothed shrew, Crocidura russula

A selection gradient was recently suggested as one possible cause for a clinal distribution of mitochondrial DNA (mtDNA) haplotypes along an altitudinal transect in the greater white-toothed shrew, Crocidura russula (Ehinger et al. 2002). One mtDNA haplotype (H1) rare in lowland, became widespread when approaching the altitudinal margin of the distribution. As H1 differs from the main lowland haplotype by several nonsynonymous mutations (including on ATP6), and as mitochondria play a crucial role in metabolism and thermogenesis, distribution patterns might stem from differences in the thermogenic capacity of different mtDNA haplotypes. In order to test this hypothesis, we measured the nonshivering thermogenesis (NST) associated with different mtDNA haplotypes. Sixty-two shrews, half of which had the H1 haplotype, were acclimated in November at semioutdoor conditions and measured for NST throughout winter. Our results showed the crucial role of NST for winter survival in C. russula. The individuals that survived winter displayed a higher significant increase in NST during acclimation, associated with a significant gain in body mass, presumably from brown fat accumulation. The NST capacity (ratio of NST to basal metabolic rate) was exceptionally high for such a small species. NST was significantly affected by a gender x haplotype interaction after winter-acclimation: females bearing the H1 haplotype displayed a better thermogenesis at the onset of the breeding season, while the reverse was true for males. Altogether, our results suggest a sexually antagonistic cyto-nuclear selection on thermogenesis.     

mtDNA variation in Inuit populations of Greenland and Canada: migration history and population structure

We examined 395 mtDNA control-region sequences from Greenlandic Inuit and Canadian Kitikmeot Inuit with the aim of shedding light on the migration history that underlies the present geographic patterns of genetic variation at this locus in the Arctic. In line with previous studies, we found that Inuit populations carry only sequences belonging to haplotype clusters A2 and D3. However, a comparison of Arctic populations from Siberia, Canada, and Greenland revealed considerable differences in the frequencies of these haplotypes. Moreover, large sample sizes and regional information about birthplaces of maternal grandmothers permitted the detection of notable differences in the distribution of haplotypes among subpopulations within Greenland. Our results cast doubt on the prevailing hypothesis that contemporary Inuit trace their all of their ancestry to so-called Thule groups that expanded from Alaska about 800-1,000 years ago. In particular, discrepancies in mutational divergence between the Inuit populations and their putative source mtDNA pool in Siberia/Alaska for the two predominant haplotype clusters, A2a and A2b, are more consistent with the possibility that expanding Thule groups encountered and interbred with existing Dorset populations in Canada and Greenland.