Population structure,colonization processes and barriers for dispersal in Polish common hamsters (Cricetus cricetus)

The phylogeographic relationships of common hamster (Cricetus cricetus) populations in Poland were determined by the analysis of three partial mtDNA sequences: control region, cytochrome b and 16S rRNA. A phylogenetic tree as well as parsimony network, consistently separate Polish common hamsters into two groups: E1 being so far specific for the area of Poland, and P3 which clusters inside a Pannonian lineage, previously described from the Carpathian Basin. Polish hamsters do not share any haplotypes with the ‘North’– lineage from Germany and Western Europe, although Poland most likely represents the main migration corridor from the eastern distribution centre to the western boundary of the species range. Fossil and DNA data indicate a very recent appearance of the E1 lineage in the Polish Uplands, probably at the very end of the last glaciation. On the other hand, the Pannonian group entered southern Poland as early as the second stadial of the last glaciation (Middle Vistulian 53.35 ka). The hamster lineages in Poland seem to show different population structures and demographic histories.     

Natural and anthropogenic influences on the population structure of white‐tailed eagles in the Carpathian Basin and central Europe

European populations of the white‐tailed eagle Haliaeetus albicilla suffered a drastic decline during the 20th century. In many countries, only a few dozen breeding pairs survived or the species disappeared completely. By today, the populations have recovered, naturally or through restocking (e.g. in Scotland or the Czech Republic). In the Carpathian Basin, which is now a stronghold in southern Europe for the species in the southern part of the distribution range with more than 500 breeding pairs, only about 50 pairs survived the bottleneck. This region provides important wintering places for individuals arriving from different regions of Eurasia. In the present study, we investigated 249 DNA samples from several European countries, using 11 microsatellites and mitochondrial control region sequences (499 bp), to answer two main questions: 1) did the Carpathian Basin population recover through local population expansion or is there a significant gene flow from more distant populations as well? 2) Does the Czech population show signs in its genetic structure of the restocking with birds of unknown origin? Our microsatellite data yielded three genetically separate lineages within Europe: northern, central and southern, the latter being present exclusively in the Carpathian Basin. Sequencing of mitochondrial DNA revealed that there is one haplotype (B12) which is not only exclusive to the Carpathian Basin but it is frequent in this population. Our results suggest that in accordance with the presumably philopatric behaviour of the species, recovery of the Carpathian Basin population was mainly local, but some of the wintering birds coming from the northern and central populations contributed to its genetic composition as well. We detected considerably higher proportions of northern birds within the Czech Republic compared to the neighbouring areas, making it likely that parents of the reintroduced birds came from northern populations.     

Phylogeography and Pleistocene refugia of the adder (Vipera berus) as inferred from mitochondrial DNA sequence data

In order to contribute to the debate about southern glacial refugia used by temperate species and more northern refugia used by boreal or cold-temperate species, we examined the phylogeography of a widespread snake species (Vipera berus) inhabiting Europe up to the Arctic Circle. The analysis of the mitochondrial DNA (mtDNA) sequence variation in 1043 bp of the cytochrome b gene and in 918 bp of the noncoding control region was performed with phylogenetic approaches. Our results suggest that both the duplicated control region and cytochrome b evolve at a similar rate in this species. Phylogenetic analysis showed that V. berus is divided into three major mitochondrial lineages, probably resulting from an Italian, a Balkan and a Northern (from France to Russia) refugial area in Eastern Europe, near the Carpathian Mountains. In addition, the Northern clade presents an important substructure, suggesting two sequential colonization events in Europe. First, the continent was colonized from the three main refugial areas mentioned above during the Lower-Mid Pleistocene. Second, recolonization of most of Europe most likely originated from several refugia located outside of the Mediterranean peninsulas (Carpathian region, east of the Carpathians, France and possibly Hungary) during the Mid-Late Pleistocene, while populations within the Italian and Balkan Peninsulas fluctuated only slightly in distribution range, with larger lowland populations during glacial times and with refugial mountain populations during interglacials, as in the present time. The phylogeographical structure revealed in our study suggests complex recolonization dynamics of the European continent by V. berus, characterized by latitudinal as well as altitudinal range shifts, driven by both climatic changes and competition with related species.     

Increased genetic structuring of isolated Salamandra salamandra populations (Caudata: Salamandridae) at the margins of the Carpathian Mountains

The traditional southern Pleistocene refugia hypothesis in Europe has lately been challenged for several animal and plant species. The Carpathian Basin, especially at the marginal regions, is one of the recently recognized biodiversity hotspots in Europe. Marginal populations are prone to have lower genetic diversity and higher genetic differentiation than central populations. Here, we examined one mitochondrial DNA fragment (D‐loop) and nine nuclear (microsatellite) loci to describe the genetic diversity and phylogeographical pattern of fire salamander (Salamandra salamandra) populations in the Carpathian Basin with focusing on the southern margins of the Western Carpathians, where isolated populations of this species are present. Analyses of microsatellites indicated reduced genetic diversity for most of the isolated populations. Based on the mitochondrial DNA, only two haplotypes were found, whereas the analyses with the nuclear markers revealed a more recent genetic split between Western (Alpine) and Eastern (Carpathian) populations, and separated the Apuseni Mountains population (part of the Western Carpathians). Using approximate Bayesian computation analyses, we identified the most probable colonization scenario for the isolated North Hungarian Carpathian Basin populations. The split between isolated salamander populations from the central populations in the Carpathian Mountains dates back to the beginning of the Late Pleistocene, while the split between most of the Hungarian populations can be associated with the Last Glacial Maximum. We found evidence for long‐time isolation between the marginal Carpathian Basin and central populations. Our results also show that S. salamandra survived glacial periods in the temperate forests of north‐east Pannonia (North Hungarian Mountains), confirming that the Carpathian Basin served as important northerly refugia during the Pleistocene climatic oscillations.     

Phylogeography of field voles (Microtus agrestis) in Eurasia inferred from mitochondrial DNA sequences

In a distribution-wide phylogeographic survey of the field vole (Microtus agrestis), 75 specimens from 56 localities across Eurasia were examined for DNA sequence variation along the whole 1140 base pair (bp) mitochondrial (mt) cytochrome b gene. The species is subdivided into three main mtDNA phylogeographic groups - western, eastern and southern - with largely allopatric distributions. The western phylogeographical group is found in west and central Europe and spread most probably from a glacial refugium in the Carpathians. The eastern group covers a large range from Lithuania to central Asia, and probably originated from a southeast European source (e.g. the southern Urals or the Caucasus). The southern group occupies an area from Portugal to Hungary, with division into two distinct mtDNA sublineages that presumably derive from separate glacial refugia in the Iberian Peninsula. Molecular clock estimates suggest that the western and eastern field vole populations separated during the last glaciation, whereas the southern population dates back 0.5-0.9 Myr. High levels of mtDNA variation indicate relatively large population sizes and subdivisions within phylogeographic groups during the last glaciation. We report a possible new suture zone in east Europe.     

Fine-scale phylogeographical analysis of Mediterranean Anacamptis palustris (Orchidaceae) populations based on chloroplast minisatellite and microsatellite variation

The phylogeographical history of the rare marsh orchid Anacamptis palustris (Orchidaceae) was reconstructed using highly polymorphic chloroplast minisatellite and microsatellite loci. Allelic variation at chloroplast microsatellite loci was due to length variation in poly(A/T) repeats and was informative on a regional scale, but was not sufficient to unravel relationships among populations on a local geographical scale. The minisatellite locus, however, was found to be highly variable. Nine distinct repeat types were found and variation in repeat number occurred in five repeat types. The distribution of chloroplast haplotypes, combining microsatellite and minisatellite repeat type variation, provided a clear phylogeographical picture on a large geographical scale, whereas length variation in one highly polymorphic minisatellite repeat type provided fine-scale phylogeographical information. Mediterranean populations could be divided into four main lineages, a western European lineage, a northern and central Italian lineage, a well-isolated southern Italian (Apulian) lineage, and an eastern European lineage. Variation at the most variable minisatellite repeat type N revealed 19 alleles and allowed the study of seed-mediated gene flow and an estimation of the ratio of pollen to seed flow among neighbouring populations.     

Development of novel microsatellite markers to identify the different invasive lineages in the Corbicula complex and to assess androgenesis

Reliable markers are needed to identify the lineages in the invasive clam genus Corbicula. Previous studies have demonstrated that mitochondrial (mt) DNA poorly resolves Corbicula phylogeny, owing to its androgenetic reproductive mode. Moreover, hybridization and mitochondrial/nuclear mismatches occur. We developed the first eleven polymorphic markers to detect these phenomena and to investigate the nuclear identity of Corbicula populations. These microsatellite loci revealed three main lineages in Western Europe. One locus allowed rapid discrimination of these three lineages on agarose gel, saving time and money. Moreover, the eleven markers were successfully cross-amplified in the invasive Corbicula lineages found in North America.     

Holarctic phylogeography of the root vole (Microtus oeconomus): implications for late Quaternary biogeography of high latitudes

A species-wide phylogeographical study of the root vole (Microtus oeconomus) was performed using the whole 1140 base pair mitochondrial (mt) cytochrome b gene. We examined 83 specimens from 52 localities resulting in 65 unique haplotypes. Our results demonstrate that the root vole is divided into four main mtDNA phylogenetic lineages that seem to have largely allopatric distributions. Net divergence estimates (2.0-3.5%) between phylogroups, as well as relatively high nucleotide diversity estimates within phylogroups, indicate that the distinct phylogeographical structure was initiated by historical events that predated the latest glaciation. European root voles are divided into a Northern and a Central mtDNA phylogroup. The mtDNA data in concert with fossil records imply that root voles remained north of the classical refugial areas in southern Europe during the last glacial period. The currently fragmented populations in central Europe belong to a single mtDNA phylogroup. The Central Asian and the North European lineages are separated by the Ural Mountains, a phylogeographical split also found in collared lemmings (Dicrostonyx) and the common vole (M. arvalis). The Beringian lineage occurs from eastern Russia through Alaska to northwestern Canada. This distribution is congruent with the traditional boundaries of the Beringian refugium and with phylogeographical work on other organisms. In conclusion, similarities between the phylogeographical patterns in the root vole and other rodents, such as Arctic and subarctic lemmings, as well as more temperate vole species, indicate that late Quaternary geological and climatic events played a strong role in structuring northern biotic communities.     

Mitochondrial DNA and microsatellite analyses of the genetic status of the presumed subspecies Cervus elaphus montanus (Carpathian red deer)

The possibly distinct Carpathian red deer was compared genetically to other European populations. We screened 120 red deer specimens from Serbia, the Romanian lowland and the Romanian Carpathians for genetic variability using 582 bp of the mitochondrial control region and nine polymorphic nuclear microsatellite loci. The study aimed at a population genetic characterization of the Carpathian red deer, which are often treated as a distinct subspecies (Cervus elaphus montanus). The genetic integrity of the Carpathian populations was confirmed through the haplotype distribution, private alleles and genetic distances. The Carpathian red deer are thus identified as one of the few remaining natural populations of this species, deserving special attention among game and conservation biologists. The history of the populations studied, in particular the introduction of Carpathian red deer into Romanian lowland areas in the 20th century, was reflected by the genetic data.     

Circum Black Sea phylogeography of Barbus freshwater fishes: divergence in the Pontic glacial refugium

We used DNA sequence variation at the mitochondrial cytochrome b gene (1141 bp) to assess the phylogeography of Barbus fishes in the Black Sea region. Our aim was to test whether the recent ( approximately 22 000-7500 years ago) freshwater phase of the Black Sea was a conduit for gene flow among freshwater fishes that today are found in streams entering the saltwater Black Sea. Deep phylogeographical breaks suggestive of allopatric divergence were observed between four regional groups of populations. Coalescent simulation used to distinguish between this and an alternative scenario that the phylogeographical structure was due to random lineage sorting showed that the contemporary populations were unlikely (P < 0.001) to have been founded by a single ancestral population. Divergences between the lineages (0.86-2.54%) were dated to the Middle to Late Pleistocene using distances and a molecular clock corrected for superimposed substitutions. Taken together, this evidence suggests that multiple refugial populations survived over several later glaciations in the vicinity of the Black Sea. This Pontic refugium served as the primary source for the postglacial expansion throughout Europe as far as the Atlantic basin. However, only one of the phylogeographical lineages contributed to this dispersion, whereas the others remain restricted to the Black Sea region and followed independent evolutionary trajectories.     

Identification of the barrier to gene flow between phylogeographic lineages of the common hamster <Emphasis Type="Italic">Cricetus cricetus</Emphasis>

In anthropogenically disturbed habitats, natural barriers still exist and have to be recognized, as they are important for conservation measures. Areas of phylogeographic breaks within a species are often stabilized in inhospitable regions which act as natural barriers. An area of contact between phylogeographic lineages of the common hamster (Cricetus cricetus) was found in the Małopolska Upland in Poland. A total of 142 common hamsters were captured between 2005 and 2009. All hamsters were genotyped at 17 microsatellite loci and partial sequences of the mitochondrial (mtDNA) control region were obtained. No mixed populations with mtDNA haplotypes of both lineages were found. The distance between marginal populations was about 20 km; no hamsters were found in the area between. A principal components analysis (PCA) was performed on microsatellite data and the greatest change in PC1 scores was found between marginal samples. To define the habitat components responsible for the phylogeographic break, we compared the habitat composition of sites occupied by hamsters with those from which hamsters were absent. We found that hamsters avoided forested areas and sandy soils. The area of the potential barrier was characterized by a high proportion of woodland and unfavorable soils in comparison with neighboring areas inhabited by hamsters. They cannot settle in this area due to their high winter mortality in shallow burrows and high predation in the fields adjacent to forests.     

Multiple bottlenecks in threatened western European populations of the common hamster Cricetus cricetus (L.)

Common hamsters Cricetus cricetus (L.)show a highly fragmented distributionpattern across Europe. Over the last decades,human influence caused significant populationdeclines in particular at the western rangeboundary. Despite the initiation of breedingand release programs the genetic structure anddiversity of European common hamsterpopulations is largely unknown. In this study,hamsters from ten localities in five Europeancountries were investigated. Mitochondrialcontrol region was sequenced from 145 animalsrepresenting all sampled populations. 385hamster were screened for polymorphisms at 11microsatellite loci. Both marker systemsrevealed extensive genetic differentiationamong European common hamsters. Westernpopulations displayed very low levels of mtDNAdiversity (H = 0 – 0.2, Alsace, Limburg,Flanders, Baden-Wuerttemberg) compared toeastern populations from Saxony-Anhalt,Thuringia and Southern Moravia (H = 0.663– 0.816). Microsatellite analyses revealed asimilar pattern with low to moderate diversityvalues in western hamsters (A = 1.636 –5.364; H _e = 0.111 – 0.504) and highlevels of polymorphism in eastern hamsters(A = 8.909 – 9.818; H _e = 0.712– 0.786). High microsatellite based F _STmeasures (up to 0.635) suggest a typical islandmodel of distribution with no current gene flowbetween most areas. Western hamster populationsexhibit obvious similarities in mitochondrialhaplotype and microsatellite alleledistributions. Gene trees group westernhamsters consistently together on the samebranch but bootstrap values never reachedsignificance. There are strong indications thatlow diversity in western populations ispartially caused by a joint historic founderevent and not only by recent population breakdowns. Overlapping mitochondrial haplotypesprove a close association between westernhamsters and animals from the east German rangein the recent past which does not support theexistence of a separate subspecies C. c.canescens in Europe. Hamsters from southernMoravia emerged as the genetically mostdistinguished population and could be part of a different genetic lineage in Europe.     

Phylogeographical footprints of the Strait of Gibraltar and Quaternary climatic fluctuations in the western Mediterranean: a case study with the greater white-toothed shrew, Crocidura russula (Mammalia: Soricidae)

We used mitochondrial cyt b sequences to investigate the phylogenetic relationships of Crocidura russula (sensu lato) populations across the Strait of Gibraltar, western Europe, Maghreb, and the Mediterranean and Atlantic islands. This revealed very low genetic divergence between European and Moroccan populations. The application of a molecular clock previously calibrated for shrews suggested that the separation of European from Moroccan lineages occurred less than 60 000 bp, which is at least 5 million years (Myr) after the reopening of the Strait of Gibraltar. This means that an overwater dispersal event was responsible for the observed phylogeographical structure. In contrast, genetic analyses revealed that Moroccan populations were highly distinct from Tunisian ones. According to the molecular clock, these populations separated about 2.2 million years ago (Ma), a time marked by sharp alternations of dry and humid climates in the Maghreb. The populations of the Mediterranean islands Ibiza, Pantelleria, and Sardinia were founded from Tunisian populations by overwater dispersal. In conclusion, overwater dispersal across the Strait of Gibraltar, probably assisted by humans, is possible for small terrestrial vertebrates. Moreover, as in Europe, Quaternary climatic fluctuations had a major effect on the phylogeographical structure of the Maghreb biota.     

The postglacial recolonization of Northern Europe by Rana arvalis as revealed by microsatellite and mitochondrial DNA analyses

The postglacial history of the moor frog (Rana arvalis) in Northern Europe was investigated with the aid of eight variable microsatellite loci and a 661 bp sequence of the mitochondrial cytochrome b gene. A division between eastern and western mitochondrial lineages was discovered, supporting two recolonization routes to Fennoscandia since the last glacial maximum. This result was corroborated by the microsatellite data, which revealed a contact zone between the two lineages in Northern Sweden. These findings add to the increasing evidence that an intraspecific genetic biodiversity founded on the existence of eastern and western clades is a common element in Fennoscandian fauna and flora.     

The genetic structure of adders (Vipera berus) in Fennoscandia: congruence between different kinds of genetic markers

In order to elucidate the colonization history of Fennoscandian adders (Vipera berus), the phylogeographical patterns of two nuclear sets of DNA markers (random amplified polymorphic DNA and microsatellite) are compared with that previously obtained from mitochondrial DNA. An eastern and a western lineage within Fennoscandian adders is readily distinguishable using both sets of nuclear markers, corroborating the hypothesis that the lineages stem from separate glacial refugia. Moreover, the same contact zones as were derived from mitochondrial data are clearly identifiable. Both sets of nuclear markers detect a high level of admixture across one zone in northern Finland, with introgression reaching far west into Sweden.     

Mitochondrial gene diversity in the common vole Microtus arvalis shaped by historical divergence and local adaptations

The phylogeography of the common vole (Microtus arvalis) was examined by analysing mitochondrial DNA (mtDNA) sequence variation in 1044 base pairs (bp) of the cytochrome b (cytb) gene and in 322 bp of the control region (ctr) among 106 individuals from 58 locations. The geographical distribution of four previously recognized cytb evolutionary lineages in Europe was refined and a new lineage was found in southern Germany. All lineages were distributed allopatrically, except in one sample that was probably located in a contact zone. The occurrence of several lineages in the Alps is in keeping with their recent recolonization from distinct sources. The translation of 84 cytb DNA sequences produced 33 distinct proteins with relationships that differed from those of the DNA haplotypes, suggesting that the mtDNA lineages did not diverge in response to selection. In comparison with M. agrestis, a neutrality test detected no overall evidence for selection in the cytb gene, but a closer examination of a structural model showed that evolutionarily conserved and functionally important positions were often affected. A new phylogeographical test of random accumulation of nonsynonymous mutations generated significant results in three lineages. We therefore conclude that the molecular diversity of cytb in M. arvalis is overall the result of the demographic history of the populations, but that there have been several episodes of local adaptation to peculiar environments.     

Genetic Structure of Brown Trout (Salmo trutta) Populations from Turkey Based on Microsatellite Data

This present study investigated micro- and macro-geographic microsatellite DNA variations using five polymorphic microsatellite loci from 27 brown trout populations in Turkey. Average number of alleles and average observed heterozygosity were 7.4 and 0.254, respectively. Even populations from the same sea basin and river system (the so called micro-geographic regions) had unique alleles. Genetic variation among the populations from macro-geographic regions (different sea basins and river systems) was 45.78%. The mtDNA lineages of brown trout that have previously been identified by mtDNA analyses were supported by the analysis of the microsatellite DNA data in general. The Çatak population, which belongs to the Tigris lineage, was clustered together with the Euphrates populations within the Adriatic mtDNA lineage, based on microsatellite data. Both mitochondrial and microsatellite DNA analyses have made it possible to determine a secondary contact between Adriatic and Tigris lineages.     

Genetic differentiation of the marbled white butterfly, Melanargia galathea, accounts for glacial distribution patterns and postglacial range expansion in southeastern Europe

Isolation of Mediterranean species in the southern European peninsulas during the cold glacial phases often resulted in differentiation of several genetic lineages confined to the respective peninsulas. However, whilst there is good genetic evidence for multiple refugia in Iberia, there are only limited data available for the Balkans. Therefore, we wish to examine the hypothesis of a strong genetic structuring within southeastern Europe for the existence of multiple Balkan differentiation centres and/or several leading edges. As a model we use the marbled white butterfly, Melanargia galathea. We studied 18 allozyme loci of 564 individuals from 16 populations distributed over a large part of southeastern Europe. The single populations showed moderately high genetic diversity and no northward decline of genetic diversity was detected. The overall genetic differentiation between populations was considerable (F(ST) 7.0%). Cluster analysis discriminated three genetic groups: (i) a western flank in the former Yugoslavia, parts of eastern Austria and Hungary; (ii) an eastern flank with populations from Bulgaria and Romania (south of the southern Carpathians and eastern Carpathians); and (iii) the eastern Carpathian Basin. Hierarchical variance analysis distributed 53% of the variance among populations between these three groups. One sample from the Greek-Bulgarian border clustered within the eastern flank, but showed some tendency towards the eastern Carpathian Basin populations. Two populations from Carinthia clustered together with the eastern Carpathian Basin ones and a population from Styria showed an intermediate genetic composition between the three groups. Most probably, the eastern and the western flank groups are due to postglacial range expansion from the northeastern and the northwestern edges of the glacial differentiation centre (so-called leading edges). The eastern Carpathian Basin group may have resulted from postglacial expansion from northern Greece through valley systems of the central Balkan peninsula, maybe even expanding westwards north of the Balkan mountains reaching some parts of eastern Austria (e.g. Carinthia). Therefore, the Balkanic refugium of M. galathea may or may not have been continuous along the coastal areas of the Mediterranean, but must have been strongly genetically structured.     

Phylogeography of a subalpine tall‐herb Ranunculus platanifolius (Ranunculaceae) reveals two main genetic lineages in the European mountains

A phylogeographical analysis of Ranunculus platanifolius, a typical European subalpine tall‐herb species, indicates the existence of two main genetic lineages based on amplified fragment length polymorphism (AFLP) markers. One group comprises populations from the Balkan Peninsula and the south‐eastern Carpathians and the other includes the remaining part of the range of the species, encompassing the western Carpathians, Sudetes, Alps, Pyrenees and Scandinavia. The main phylogeographical break observed in this species runs across the Carpathians and separates the main parts of this range (western and south‐eastern Carpathians), supporting a distinct glacial history of populations in these areas. The high genetic similarity of the Balkan Peninsula and south‐eastern Carpathian populations could indicate a common glacial refugium for these contemporarily isolated areas of species distribution. The western and northern part of the species range displays an additional weak differentiation into regional phylogeographical groups, which could have been shaped by isolation in glacial refugia or even by a postglacial isolation. The observed weak phylogeographical structure could also be linked with ecological requirements, allowing survival along streams in relatively low, forested mountain ranges. © 2013 The Linnean Society of London     

Molecular characterization of clonal population structure and biogeography of arctic apomictic Daphnia from Greenland and Iceland

As part of a continuing international project to characterize the population genetic (clonal) structure of arctic members of the Daphnia pulex complex, 34 populations from western Iceland (N= 1373), and 76 populations from western Greenland (N= 2917), were surveyed for allozymic variation at six polymorphic enzyme loci. Mean clonal richness (±SE) was 1.91±0.19 and 1.50±0.12 for Iceland and Greenland populations, respectively. Mean clonal diversity (±1 SE) was 1.20±0.07 and 1.13±0.04 for Iceland and Greenland populations, respectively. Four widely distributed clones constituted 92.2% of the total animals surveyed from Iceland, while three locally abundant clones constituted 80.1% of the total animals collected primarily from Disko Island, western Greenland. Selected populations were screened for mitochondrial (mt)DNA variation using PCR-based RFLP analysis of a 2100 bp fragment containing part of the ND4 and ND5 genes. One mtDNA haplotype was very widespread in both western Greenland and western Iceland, although, a number of mutational derivatives were also detected. These data indicate the potential for long-distance dispersal of mtDNA lineages, of the order of hundreds or thousands of kilometers across the arctic. Phylogenetic analysis of the sequence of a 254 base pair (bp) fragment of the control region of the mtDNA molecule revealed two major clades one of which consisted solely of non-melanic lineages, and the other of which consisted almost exclusively of melanic lineages (i.e. one non-melanic lineage also clustered in this clade). Sequence divergence between the two clades averaged 7.3%. Both mitochondrial analyses did not reveal any distinct intraregional clustering of lineages. We discuss our results in reference to previous molecular work done on this arctic Daphnia complex, and we attempt to infer phylogeographic patterning based on geological/glaciological historical events in this region of the arctic.