Micro- and macrogeographical genetic structure of colonies of naked mole-rats Heterocephalus glaber

Patterns of genetic structure in eusocial naked mole-rat populations were quantified within and among geographically distant populations using multilocus DNA fingerprinting and mitochondrial DNA (mtDNA) sequence analysis. Individuals within colonies were genetically almost monomorphic, sharing the same mtDNA control region haplotype and having coefficients of band sharing estimated from DNA fingerprints ranging from 0.93 to 0.99. Family analysis of a hybrid captive colony of naked mole-rats with increased levels of genetic variability using multilocus DNA fingerprinting gave results consistent with Mendelian inheritance, and has revealed for the first time that multiple paternity can occur. In a survey of wild colonies from Ethiopia, Somalia and locations in northern and southern Kenya, we have examined mtDNA control region sequence variation in 42 individuals from 15 colonies, and together with multilocus DNA fingerprinting and mtDNA cytochrome- b sequence analysis in selected individuals have shown that these populations show considerable genetic divergence. Most of the variance in sequence divergence was found to be between geographical locations (Φ_ct= 0.68) and there was a significant correlation between sequence divergence and geographical separation of haplotypes. Six colonies from Mtito Andei in southern Kenya shared the same control region haplotype, suggesting a recent common maternal ancestor. In contrast, out of four colonies at Lerata in north Kenya, three haplotypes were identified, and phylogenetic analysis suggests that this area may be a zone where two distinct lineages are in close proximity. Genetic distances were maximal between Ethiopian and southern Kenyan populations at 5.8% for cytochrome- b , and are approaching interspecific values seen between other Bathyergids.     

Genetic structure within and among populations of the endangered razorback sucker (Xyrauchen texanus) as determined by analysis of microsatellites

Razorback sucker (Xyrauchen texanus) was once common and widely distributed throughout the Colorado River drainage of western North America. Water development and predation by non-native species led to significant decrease in the species’ range, and dramatic reduction in size of remaining populations. Previous analyses of mtDNA variation determined that most variation was found within locations and that haplotypes were randomly distributed relative to geography, indicating these samples represent remnants of a single, basin-wide population. In addition, both diversity and number of haplotypes declined progressively down- to upstream, consistent with geologically-recent expansion into the northern portions of the basin. Analyses of variation at 13 microsatellite loci also identified a decrease in genetic variation from down- to upstream, also consistent with the hypothesis of recent expansion. Analyses of population structure identified three distinct groups, but the majority of microsatellite variation was found within populations. Most individuals from the upper Colorado River were identified as a discrete unit. These individuals exhibited high levels of relatedness, indicating this represented an isolated group of closely related individuals. There also were significant differences between populations above and below the Grand Canyon; however, estimates of Θ were relatively low. Given nothing is known of local adaptation in this species, populations above and below the canyon should be managed as independent units; however, if numbers become too low it will be possible to translocate individuals from southern populations northward to increase levels of genetic variability and decrease relatedness within units. These results also illustrate the need for careful consideration of all available information when using molecular data in identifying units for management.     

Tripartite genetic subdivisions in the ornate shrew (Sorex ornatus)

We examined cytochrome b sequence variation in 251 ornate shrews (Sorex ornatus) from 20 localities distributed throughout their geographical range. Additionally, vagrant (S. vagrans) and montane (S. monticolus) shrews from four localities were used as outgroups. We found 24 haplotypes in ornate shrews from California (USA) and Baja California (Mexico) that differed by 1-31 substitutions in 392 bp of mitochondrial DNA (mtDNA) sequence. In a subset of individuals, we sequenced 699 bp of cytochrome b to better resolve the phylogeographic relationships of populations. The ornate shrew is phylogeographically structured into three haplotype clades representing southern, central and northern localities. Analysis of allozyme variation reveals a similar pattern of variation. Several other small California vertebrates have a similar tripartite pattern of genetic subdivision. We suggest that topographic barriers and expansion and contraction of wetland habitats in the central valley during Pleistocene glacial cycles account for these patterns of genetic variation. Remarkably, the northern ornate shrew clade is phylogenetically clustered with another species of shrew suggesting that it may be a unique lowland form of the vagrant shrew that evolved in parallel to their southern California counterparts.     

Phylogeography of two European newt species--discordance between mtDNA and morphology

The newts Triturus vulgaris and Triturus montandoni are sister species that exhibit contrasting levels of intraspecific morphological variation. Triturus vulgaris has a broad Eurasiatic distribution encompassing both formerly glaciated and unglaciated areas and shows substantial morphological differentiation in the southern part of its range, while T. montandoni, confined to the Carpathians, is morphologically uniform. We analysed sequence variation of two mtDNA fragments of the total length of c. 1850 bp in 285 individuals of both species collected from 103 localities. Phylogenetic analysis of 200 unique haplotypes defined 12 major clades, their age estimated at c. 4.5-1.0 million years (Myr). Most of the older clades were found in the southern part of the range, and also in central Europe, mainly in Romania. The distribution of mtDNA clades points to the existence of several glacial refugia, located in the Caucasus region, Anatolia, the Balkan Peninsula, Italy, and more to the north in central Europe. The concordance between mtDNA based phylogeny and the distribution of T. vulgaris subspecies was weak. Triturus montandoni haplotypes did not form a monophyletic group. Instead they were found in six clades, in five of them mixed with T. vulgaris haplotypes, most likely as a result of past or ongoing hybridization and multiple introgression of mtDNA from T. vulgaris to T. montandoni. Patterns of sequence variation within clades suggested long-term demographic stability in the southern groups, moderate and relatively old demographic growth in the populations inhabiting central Europe, and high growth in some of the groups that colonized northern parts of Europe after the last glacial maximum.     

Genetic differences between the endangered San Clemente Island loggerhead shrike Lanius ludovicianus mearnsi and two neighbouring subspecies demonstrated by mtDNA control region and cytochrome b sequence variation

We investigated mtDNA sequence variation in five populations of the loggerhead shrike Lanius ludovicianus , representing four subspecies, including the San Clemente loggerhead shrike L. l. mearnsi , a critically endangered California Channel Island endemic. Variability in 200 bp of control region and 200 bp of cytochrome b was extremely low, and defined four haplotypes. Strong structure was apparent among all three southern Californian subspecies, including L. l. mearnsi , with one haplotype predominating in each subspecies. Although potential levels of gene flow between L. l. mearnsi and neighbouring populations are low, mtDNA data support field observations that some shrikes visit the island during winter but do not stay to breed, and suggest that these birds come from the mainland. The similarity in haplotypes between populations from Saskatchewan, Canada and those in southern California suggests post-glacial northern range expansion of the species. Our results confirm the evolutionary distinctiveness of L. l. mearnsi and justify continuing efforts for its conservation.     

Genetic diversity and phylogenetic origin of brown trout Salmo trutta populations in eastern Balkans

The study focuses on the phylogenetic origin and genetic diversity of brown trout in the eastern part of the Balkan Peninsula. It further aims to reveal the impact of human-mediated transfers and stocking with non-indigenous trout on the populations in this area. For these purposes, mtDNA control region and microsatellite variation of 204 individuals from 16 populations were analysed. The results indicate that mtDNA haplotypes from the lower Danube basin and southern Black Sea basins differ substantially from a subclade of the Danubian lineage consisting of haplotypes found so far in the most of the Danube basin and in the Caspian and Aral Sea basins. Considering also the results of demographic analyses, this study evidences a complex evolutionary history of brown trout in the southern and western parts of the Black Sea basin. In the Aegean Sea basin, a high frequency of the central haplotype of Adriatic mtDNA lineage has been found. The other Adriatic lineage haplotypes found in this basin differ from the central haplotype by one mutational step only, indicating a recent evolution of the Adriatic lineage in the Aegean Sea basin. Substantial genetic differentiation among populations and basins was revealed. The hybridization with Atlantic brown trout was indicated in both sea basins, but especially in the Danube basin. Compared to other European regions, it can be inferred that the introgression of exogenous brown trout in the eastern Balkan populations is rather low.     

Variation of the mitochondrial DNA control region in the populations of southern form of Dolly Varden (<Emphasis Type="Italic">Salvelinus malma krascheninnikovi</Emphasis>) from Sakhalin

Analysis of a 551-bp segment of the mitochondrial DNA control region in 23 individuals from nine populations of Dolly Varden from Sakhalin and three individuals from the Shikaribetsu Lake (Hokkaido) revealed the presence of seven haplotypes of southern form, along with one haplotype of northern form of Dolly Varden. All seven haplotypes of southern Dolly Varden were earlier described in the populations from Hokkaido. Hierarchical analysis of molecular variance (AMOVA) based on the haplotype frequencies, performed using literature data, suggested that, during the glacial epoch, there were three regional population groups of Dolly Varden (from eastern and western coasts of Sakhalin, and from Southern Primorye). Population groups from Sakhalin and Primorye were clearly separated. The differences between two Sakhalin population groups in the mtDNA haplotype frequencies were not statistically significant. However, relative to the earlier obtained data on microsatellite loci, these differences were statistically significant. For the populations of Sakhalin Dolly Varden, the data on mitochondrial and microsatellite DNA variation supplement each other.     

Population genetics of shortnose sturgeon Acipenser brevirostrum based on mitochondrial DNA control region sequences

Shortnose sturgeon is an anadromous North American acipenserid that since 1973 has been designated as federally endangered in US waters. Historically, shortnose sturgeon occurred in as many as 19 rivers from the St. John River, NB, to the St. Johns River, FL, and these populations ranged in census size from 10(1) to 10(4), but little is known of their population structure or levels of gene flow. We used the polymerase chain reaction (PCR) and direct sequence analysis of a 440 bp portion of the mitochondrial DNA (mtDNA) control region to address these issues and to compare haplotype diversity with population size. Twenty-nine mtDNA nucleotide-substitution haplotypes were revealed among 275 specimens from 11 rivers and estuaries. Additionally, mtDNA length variation (6 haplotypes) and heteroplasmy (2-5 haplotypes for some individuals) were found. Significant genetic differentiation (P < 0.05) of mtDNA nucleotide-substitution haplotypes and length-variant haplotypes was observed among populations from all rivers and estuaries surveyed with the exception of the Delaware River and Chesapeake Bay collections. Significant haplotype differentiation was even observed between samples from two rivers (Kennebec and Androscoggin) within the Kennebec River drainage. The absence of haplotype frequency differences between samples from the Delaware River and Chesapeake Bay reflects a probable current absence of spawning within the Chesapeake Bay system and immigration of fish from the adjoining Delaware River. Haplotypic diversity indices ranged between 0.817 and 0.641; no relationship (P > 0.05) was found between haplotype diversity and census size. Gene flow estimates among populations were often low (< 2.0), but were generally higher at the latitudinal extremes of their distribution. A moderate level of haplotype diversity and a high percentage (37.9%) of haplotypes unique to the northern, once-glaciated region suggests that northern populations survived the Pleistocene in a northern refugium. Analysis of molecular variance best supported a five-region hierarchical grouping of populations, but our results indicate that in almost all cases populations of shortnose sturgeon should be managed as separate units.     

Population genetic structure of the seed pathogen Pyrenophora semeniperda on Bromus tectorum in western North America

We examined genetic variation in the ascomycete pathogen Pyrenophora semeniperda cultured from seeds of the invasive grass Bromus tectorum in the Intermountain West of North America. We sequenced the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA genome in 417 monoconidial cultures collected from 20 sites in Washington, Idaho, Utah and Colorado, USA. ITS sequence diversity was surprisingly high; 12 unique haplotypes were identified, averaging 1.3% pairwise sequence divergence. All sites had at least two haplotypes present, and three sites had seven or more. One haplotype composed 60% of the isolates and occurred at all 20 locations; the remaining haplotypes generally occurred at low frequencies within sites but at multiple sites throughout the region. Sites in Washington and Idaho were more diverse than those in Utah and Colorado, averaging two more haplotypes and 67% more pairwise differences among haplotypes at a site. Analysis of molecular variance (AMOVA) indicated that more than 80% of the genetic variation was found within sampling locations, while 7-11% of the variation can be attributed to differences between northern (Washington and Idaho) and southern (Utah and Colorado) populations. The wide distribution of even uncommon haplotypes among sampling sites and weak correlations between genetic and geographic distances among populations (< 0.2) suggested that these populations recently were established from a common source. We hypothesize that the strains of P. semeniperda infecting B. tectorum in western North America probably arrived with the invasive grass from its native Eurasian range.     

Analysis of Human Mitochondrial DNA Polymorphisms in the Japanese Population

The highly polymorphic nature and high amplification efficiency of mitochondrial DNA (mtDNA) is valuable for the analysis of biological evidence in forensic casework, such as the identification of individuals and assignment of race/ethnicity. To be useful, a mtDNA polymorphism database for the Japanese population requires an understanding of the range of haplotype variation and phylogenies of mtDNA sequences. To extend current knowledge on the haplotypes in the Japanese population, this study defines new lineages and provides more detail about some of those previously described. We compared the hypervariable regions (HVRs) of 270 healthy, unrelated Japanese individuals and demonstrated 192 haplotypes. Combining HVR1 and HVR2, the genetic diversity was 0.9935, thus providing a high level of identification capability. Haplogroup status was defined for 160 individuals using HVR1, HVR2, and particular coding region polymorphisms; these individuals belonged to 94 haplotypes, four of which were new lineages. The complete mtDNA sequence was also determined from seven individuals.     

Mitochondrial haplotype diversity among Portuguese brown trout Salmo trutta L. populations: relevance to the post-pleistocene recolonization of northern Europe

Mitochondrial haplotype diversity in seven Portuguese populations of brown trout, Salmo trutta L., was investigated by sequencing the 5' end of the mitochondrial DNA (mtDNA) control region. Five new haplotypes were described for this species, each two to three mutational steps distant from the common north Atlantic haplotype. Significant population subdivision of mtDNA haplotypes was also apparent. Based on these results, as well as on published data describing the distribution of both mtDNA haplotypes and allozyme alleles throughout Europe, the postglacial recolonization of northern Europe was re-evaluated. It is argued that the available data do not support the contribution of two major glacial refugia (southwest Atlantic and Ponto-Caspian Basin) to this postglacial recolonization, as proposed in a recently published model. The unique genetic architecture of Portuguese brown trout within the Atlantic-basin clade of this species represents a highly valuable genetic resource that should be protected from introgression with nonendemic strains of hatchery fish.     

Genetic diversity in an Andean population from Peru and regional migration patterns of Amerindians in South America: data from Y chromosome and mitochondrial DNA

The genetic variability of a Quechua-speaking Andean population from Peru was examined on the basis of four Y chromosome markers and restriction sites that define the Amerindian mitochondrial DNA (mtDNA) haplogroups. Forty-nine out of 52 (90.4%) individuals had mtDNA which belonged to one of the four common Amerindian haplogroups, with 54% of the samples belonging to haplogroup B. Among 25 males, 12 had an Amerindian Y chromosome, which exists as four haplotypes defined on the basis of the DYS287, DYS199, DYS392 and DYS19 markers, three of which are shared by Amazonian Amerindians. Thus, there is a clear directionality of marriages, with an estimated genetic admixture with non-Amerindians that is 9 times lower for mtDNA than for Y chromosome DNA. The comparison of mtDNA of Andean Amerindians with that of people from other regions of South America in a total of 1,086 individuals demonstrates a geographical pattern, with a decreasing frequency of A and C haplotypes and increasing frequency of the D haplotype from the north of the Amazon River to the south of the Amazon River, reaching the lowest and the highest frequencies, respectively, in the more southern populations of Chile and Argentina. Conversely, the highest and lowest frequencies of the haplogroup B are found, respectively, in the Andean and the North Amazon regions, and it is absent from some southern populations, suggesting that haplotypes A, C and D, and haplotype B may have been dispersed by two different migratory routes within the continent.     

Genetic evidence for glacial refugia of the temperate tree Eucryphia cordifolia (Cunoniaceae) in southern South America

? Premise of the study: The temperate forests of southern South America were greatly affected by glaciations. Previous studies have indicated that some cold-tolerant tree species were able to survive glacial periods in small, ice-free patches within glaciated areas in the Andes and in southern Patagonia. Here we asked whether populations of the mesothermic species Eucryphia cordifolia also were able to survive glaciations in these areas or only in unglaciated coastal areas. ? Methods: The chloroplast intergenic spacer trnV-ndhC was sequenced for 150 individuals from 22 locations. Genetic data were analyzed (standard indexes of genetic diversity, a haplotype network, and genetic differentiation) in a geographical context. ? Key results: Two of the nine haplotypes detected were widespread in high frequency across the entire range of the species. The highest levels of genetic diversity were found around 40°S, decreasing sharply northward and more moderately southward. No differences in genetic diversity were found between Andean and coastal populations. Notably, seven haplotypes were found in a small area of the Coast Range known as the Cordillera Pelada (40°S). The differentiation coefficients G(ST) and N(ST) revealed that most of the genetic variation detected was due to variation within populations. ? Conclusions: The low levels of population differentiation and the high genetic diversity found in the Cordillera Pelada suggest that this area was the main refugium for E. cordifolia during glaciations. Nevertheless, given the high levels of genetic diversity found in some Andean populations, we cannot discount that some local populations also survived the glaciation in the Andes.     

Phylogeography of a parasitoid wasp (Diaeretiella rapae): no evidence of host-associated lineages

The exceptional diversity of insects is often attributed to the effects of specialized relationships between insects and their hosts. Parasite-host interactions are influenced by current natural selection and dispersal, in addition to historical effects that may include past selection, vicariance, and random genetic drift. Both current and historical events can lead to reduced fitness on some hosts. If trade-offs in fitness on alternate hosts are common, adaptation to one host can prevent adaptation to another, giving rise to genetic differentiation among host-associated lineages. Previous studies of Diaeretiella rapae (Hymenoptera: Aphidiidae), a parasitoid of aphids, have revealed additive genetic differences in performance between populations that parasitize different aphid host species. To determine whether D. rapae populations collected from different aphid hosts have diverged into genetically independent lineages, we constructed a haplotype network based on sequence variation in mitochondrial DNA (mtDNA). We used single strand conformation polymorphism (SSCP) analysis to examine 2041 base pairs of mtDNA and to identify nucleotide sequences of 42 unique SSCP haplotypes. We found no association between mtDNA haplotypes and host species in either the ancestral range (Europe, Mediterranean region, Middle East, Asia) or part of the introduced range (western North America). Haplotypes likely to be ancestral were geographically widespread and found on both hosts, suggesting that the ability to use both hosts evolved prior to the diversification of the mtDNA. Ongoing gene flow appears to prevent the formation of host races.     

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.     

Low genetic diversity and significant structuring of the common hamster populations <Emphasis Type="Italic">Cricetus cricetus</Emphasis> in Poland revealed by the mtDNA control region sequence variation

The genetic diversity of 12 populations in the present range of the common hamster Cricetus cricetus (Linnaeus, 1758) in Poland was established. The 366 bp of the mtDNA control region was sequenced for 195 individuals. As few as seven haplotypes were found and their distribution was geographically structured. The large geographic areas were fixed or almost fixed for a single haplotype and three groups of populations, that do not share any haplotypes, have been defined. Proportions of genetic diversity attributable to variation between groups of populations, between populations within groups and within populations were 93.64, 1.92 and 4.45% (SAMOVA: p < 0.001 for all estimates), respectively. Such pattern of variation is most probably the result of historical, postglacial bottlenecks and present genetic drift after the population decline in the last few decades.     

mtDNA variation of the critically endangered hawksbill turtle (Eretmochelys imbricata) nesting on Iranian islands of the Persian Gulf

Genetic diversity of sea turtles (hawksbill turtle) was studied using sequencing of mitochondrial DNA (mtDNA, D-loop region). Thirty dead embryos were collected from the Kish and Qeshm Islands in the Persian Gulf. Analysis of sequence variation over 890 bp of the mtDNA control region revealed five haplotypes among 30 individuals. This is the first time that Iranian haplotypes have been recorded. Nucleotide and haplotype diversity was 0.77 and 0.001 for Qeshm Island and 0.64 and 0.002 for Kish Island, respectively. Total haplotype diversity was calculated as 0.69, which demonstrates low genetic diversity in this area. The data also indicated very high rates of migration between the populations of these two islands. A comparison of our data with data from previous studies downloaded from a gene bank showed that turtles of the Persian Gulf migrated from the Pacific and the Sea of Oman into this area. On the other hand, evidence of migration from populations to the West was not found.     

Genetic consequences of postglacial range expansion in two codistributed rodents (genus Dipodomys) depend on ecology and genetic locus

How does range expansion affect genetic diversity in species with different ecologies, and do different types of genetic markers lead to different conclusions? We addressed these questions by assessing the genetic consequences of postglacial range expansion using mitochondrial DNA (mtDNA) and nuclear restriction site‐associated DNA (RAD) sequencing in two congeneric and codistributed rodents with different ecological characteristics: the desert kangaroo rat (Dipodomys deserti), a sand specialist, and the Merriam's kangaroo rat (Dipodomys merriami), a substrate generalist. For each species, we compared genetic variation between populations that retained stable distributions throughout glacial periods and those inferred to have expanded since the last glacial maximum. Our results suggest that expanded populations of both species experienced a loss of private mtDNA haplotypes and differentiation among populations, as well as a loss of nuclear single‐nucleotide polymorphism (SNP) private alleles and polymorphic loci. However, only D. deserti experienced a loss of nucleotide diversity (both mtDNA and nuclear) and nuclear heterozygosity. For all indices of diversity and differentiation that showed reduced values in the expanded areas, D. deserti populations experienced a greater degree of loss than did D. merriami populations. Additionally, patterns of loss in genetic diversity in expanded populations were substantially less extreme (by two orders of magnitude in some cases) for nuclear SNPs in both species compared to that observed for mitochondrial data. Our results demonstrate that ecological characteristics may play a role in determining genetic variation associated with range expansions, yet mtDNA diversity loss is not necessarily accompanied by a matched magnitude of loss in nuclear diversity.     

Colonization history of north European field voles (Microtus agrestis) revealed by mitochondrial DNA

The genetic structure of field vole (Microtus agrestis) populations from northern Europe was examined by restriction fragment length polymorphisms of mitochondrial DNA (mtDNA) in 150 individuals from 67 localities. A total of 83 haplotypes was observed, most of which were rare and highly localized geographically. Overall nucleotide diversity was high (134%), but showed a tendency to decrease with higher latitude. Two major mtDNA lineages differing by 2% in nucleotide sequence were identified. A southern mtDNA lineage was observed in field voles from Britain, Denmark and southern and central Sweden, whereas voles from Finland and northern Sweden belonged to a northern lineage. The strict phylogeographic pattern suggests that the present population generic structure in field voles reflects glacial history: the two groups are derived from different glacial refugia, and recolonized Fennoscandia from two directions. A 150–200-km-wide secondary contact zone between the two mtDNA groups was found in northern Sweden. Distinct phylogeographic substructuring was observed within both major mtDNA groups.