The Geography of the Stationary Gene Migration Rate in the Human Population of Northern Eurasia

Approximation of the empirical distribution of gene frequencies by a theoretical steady-state distribution was used to obtain a geographical distribution of the limiting gene migration rates in the Northern Eurasian population. The rate averaged over the map was = 0.0432 ± 0.0003. A geographical map of ²values, which reflect the local nonstationarity character of genetic processes and intensity of selection on the distribution of gene frequencies, is presented. Over 90.1% of Northern Eurasia, the ²values satisfy the goodness-of-fit test at a significance level of = 0.1. The geographical distribution that characterizes the ratio between the stepping-stone and island properties of the population migration structure has been obtained. Combined analysis of the spatial characteristics of population migration structure demonstrated that the Pacific coast of Eurasia has played a special role in population genetic processes. This is most likely related to populating the Far East by humans in the remote past and, probably, their more recent expansion to North America through Beringia. The Caucasian region is shown to be extremely stable in terms of the stationarity of migration processes, which agrees with the general view on traditional Caucasian isolates.     

A method of evaluating the stationary rate of gene migration (a cartographic approach)

A method of geographic mapping of the stationary (limiting) gene migration rate has been developed. The method is based on approximation of the empirical distribution of gene frequencies by a theoretical steady-state distribution. The maximum likelihood method and the chi 2 minimization method are used to obtain consistent estimations of the gene migration rate as a parameter of the steady-state distribution. The new method makes it possible to determine the geographical distribution of the ratio between the properties of the population migration structure described by the stepping-stone and island models and to construct a geographical map of chi 2 values. This map approximately reflects the distribution of natural selection pressure on the gene pool if genetic processes are quasisteady.     

Estimation of the Stationary Gene Migration Rate: A Cartographic Approach

A method of geographic mapping of the stationary (limiting) gene migration rate has been developed. The method is based on approximation of the empirical distribution of gene frequencies by a theoretical steady-state distribution. The maximum likelihood method and the ² minimization method are used to obtain consistent estimations of the gene migration rate as a parameter of the steady-state distribution. The new method makes it possible to determine the geographical distribution of the ratio between the properties of the population migration structure described by the stepping-stone and island models and to construct a geographical map of ² values. This map approximately reflects the distribution of natural selection pressure on the gene pool if genetic processes are quasisteady.     

Geography of genetic processes in the population: genetic migration in Northern Eurasia (Central Asia region)]

Based on the data of the census of 1970, a map of the rates of gene migrations in the rural population of Central Asia and Kazakhstan was drawn. The corrected average value for 35 populations of oblasts (administrative regions) and autonomous republics was m = 0.0606 +/- 0.0102. The estimate obtained from the mapped data was 0.0799 +/- 0.0014, which is 1.2-fold higher than similar values for Europe. The relationship between the rate of gene migration m, the genetically effective population size Ne, and the density of elementary populations in the studied area Pp was analyzed by means of correlation and regression analyses. The following relationship was obtained: m = A/Ne + BPp, where A > 0 and B < 0. This was accounted for by the fact that the migration flow is mainly directed to the less densely populated rural areas. Given that the region was chosen somewhat artificially, studying gene migrations in Central Asia and Kazakhstan as separate historical, geographic, and genetic subregions of northern Eurasia might be a better approach.     

Genetic structure in large, continuous mammal populations: the example of brown bears in northwestern Eurasia

Knowledge of population structure and genetic diversity and the spatio-temporal demographic processes affecting populations is crucial for effective wildlife preservation, yet these factors are still poorly understood for organisms with large continuous ranges. Available population genetic data reveal that widespread mammals have for the most part only been carefully studied at the local population scale, which is insufficient for understanding population processes at larger scales. Here, we provide data on population structure, genetic diversity and gene flow in a brown bear population inhabiting the large territory of northwestern Eurasia. Analysis of 17 microsatellite loci indicated significant population substructure, consisting of four genetic groups. While three genetic clusters were confined to small geographical areas-located in Estonia, southern Finland and Leningrad oblast, Russia-the fourth cluster spanned a very large area broadly falling between northern Finland and the Arkhangelsk and Kirov oblasts of Russia. Thus, the data indicate a complex pattern where a fraction of the population exhibits large-scale gene flow that is unparalleled by other wild mammals studied to date, while the remainder of the population appears to have been structured by a combination of demographic history and landscape barriers. These results based on nuclear data are generally in good agreement with evidence previously derived using mitochondrial markers, and taken together, these markers provide complementary information about female-specific and population-level processes. Moreover, this study conveys information about spatial processes occurring over multiple generations that cannot be readily gained using other approaches, e.g. telemetry.     

Comparative phylogeography and demographic history of the wood lemming (Myopus schisticolor): implications for late Quaternary history of the taiga species in Eurasia

The association between demographic history, genealogy and geographical distribution of mitochondrial DNA cytochrome b haplotypes was studied in the wood lemming (Myopus schisticolor), a species that is closely associated with the boreal forest of the Eurasian taiga zone from Scandinavia to the Pacific coast. Except for a major phylogeographic discontinuity (0.9% nucleotide divergence) in southeastern Siberia, only shallow regional genetic structure was detected across northern Eurasia. Genetic signs of demographic expansions imply that successive range contractions and expansions on different spatial scales represented the primary historical events that shaped geographical patterns of genetic variation. Comparison of phylogeographic structure across a taxonomically diverse array of other species that are ecologically associated with the taiga forest revealed similar patterns and identified two general aspects. First, the major south-north phylogeographic discontinuity observed in five out of six species studied in southeastern Siberia and the Far East implies vicariant separation in two different refugial areas. The limited distribution range of the southeastern lineages provides no evidence of the importance of the putative southeastern refugial area for postglacial colonization of northern Eurasia by boreal forest species. Second, the lack of phylogeographic structure associated with significant reciprocal monophyly and genetic signatures of demographic expansion in all nine boreal forest animal species studied to date across most of northern Eurasia imply contraction of each species to a single refugial area during the late Pleistocene followed by range expansion on a continental scale. Similar phylogeographic patterns observed in this taxonomically diverse set of organisms with different life histories and dispersal potentials reflect the historical dynamics of their shared environment, the taiga forest in northern Eurasia.     

Geographic structure of genetic variation in the widespread woodland grass Milium effusum L. A comparison between two regions with contrasting history and geomorphology.

Allozyme variation in the forest grass Milium effusum L. was studied in 21-23 populations within each of two equally sized densely sampled areas in northern and southern Sweden. In addition, 25 populations from other parts of Eurasia were studied for comparison. The structure of variation was analysed with both diversity statistics and measures based on allelic richness at a standardised sample size. The species was found to be highly variable, but no clear geographic patterns in the distribution of alleles or in overall genetic differentiation were found, either within the two regions or within the whole sample. Thus, no inferences about the direction of postglacial migration could be made. Obviously, migration and gene flow must have taken place in a manner capable of randomising the distribution of alleles. However, there were clear differences in levels and structuring of the variation between the two regions. Levels of variation, both in terms of genetic diversity and allelic richness, were lower in northern Sweden as compared with southern Sweden. In contrast, different measures of geographic structure all showed higher levels of population differentiation in the northern region. This is interpreted as due to different geomorphological conditions in the two regions, creating a relatively continuous habitat and gene flow in the southern region as compared with the northern region where the species, although common, is confined to narrow and mutually isolated corridors in the landscape.     

Genetic Structure and Demographic History Reveal Migration of the Diamondback Moth Plutella xylostella (Lepidoptera: Plutellidae) from the Southern to Northern Regions of China

The diamondback moth Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) is one of the most destructive insect pests of cruciferous plants worldwide. Biological, ecological and genetic studies have indicated that this moth is migratory in many regions around the world. Although outbreaks of this pest occur annually in China and cause heavy damage, little is known concerning its migration. To better understand its migration pattern, we investigated the population genetic structure and demographic history of the diamondback moth by analyzing 27 geographical populations across China using four mitochondrial genes and nine microsatellite loci. The results showed that high haplotype diversity and low nucleotide diversity occurred in the diamondback moth populations, a finding that is typical for migratory species. No genetic differentiation among all populations and no correlation between genetic and geographical distance were found. However, pairwise analysis of the mitochondrial genes has indicated that populations from the southern region were more differentiated than those from the northern region. Gene flow analysis revealed that the effective number of migrants per generation into populations of the northern region is very high, whereas that into populations of the southern region is quite low. Neutrality testing, mismatch distribution and Bayesian Skyline Plot analyses based on mitochondrial genes all revealed that deviation from Hardy-Weinberg equilibrium and sudden expansion of the effective population size were present in populations from the northern region but not in those from the southern region. In conclusion, all our analyses strongly demonstrated that the diamondback moth migrates within China from the southern to northern regions with rare effective migration in the reverse direction. Our research provides a successful example of using population genetic approaches to resolve the seasonal migration of insects.     

Population subdivision in westslope cutthroat trout (Oncorhynchus clarki lewisi) at the northern periphery of its range: evolutionary inferences and conservation implications

Westslope cutthroat trout (Oncorhynchus clarki lewisi, Salmonidae) are native to the upper Columbia, Missouri, and South Saskatchewan river drainages of western North America and are at the northern periphery of their range in southeastern British Columbia, Canada. We examined geographical variation in allele frequencies at eight microsatellite loci in 36 samples of westslope cutthroat trout from British Columbia to assess levels of population subdivision and to test the hypothesis that different habitat types (principally mainstem vs. above migration barrier habitats) would influence levels of genetic diversity, genetic divergence among populations, and attainment of equilibrium between gene flow and genetic drift. Across all samples, the mean number of alleles per locus was 3.9 and mean expected heterozygosity was 0.56. Population subdivision was extensive with an overall Fst (theta) of 0.32. Populations sampled above migration barriers had significantly fewer alleles, lower expected heterozygosity, but greater average pairwise Fst than populations sampled from mainstem localities. We found evidence for isolation-by-distance from a significant correlation between genetic distance and geographical distance (r = 0.31), but the pattern was much stronger (r = 0.51) when above barrier populations and a population that may have been involved in headwater exchanges were removed. By contrast, isolation-by-distance was not observed when only above barrier populations were tested among themselves. Our data support the maintenance of separate demographic management strategies for westslope cutthroat trout inhabiting different river systems and illustrate how differing habitat structure (e.g. presence of migration barriers) may influence patterns of biodiversity and gene flow-drift equilibrium.     

A test of the influence of continental axes of orientation on patterns of human gene flow

The geographic distribution of genetic variation reflects trends in past population migrations and can be used to make inferences about these migrations. It has been proposed that the east-west orientation of the Eurasian landmass facilitated the rapid spread of ancient technological innovations across Eurasia, while the north-south orientation of the Americas led to a slower diffusion of technology there. If the diffusion of technology was accompanied by gene flow, then this hypothesis predicts that genetic differentiation in the Americas along lines of longitude will be greater than that in Eurasia along lines of latitude. We use 678 microsatellite loci from 68 indigenous populations in Eurasia and the Americas to investigate the spatial axes that underlie population-genetic variation. We find that genetic differentiation increases more rapidly along lines of longitude in the Americas than along lines of latitude in Eurasia. Distance along lines of latitude explains a sizeable portion of genetic distance in Eurasia, whereas distance along lines of longitude does not explain a large proportion of Eurasian genetic variation. Genetic differentiation in the Americas occurs along both latitudinal and longitudinal axes and has a greater magnitude than corresponding differentiation in Eurasia, even when adjusting for the lower level of genetic variation in the American populations. These results support the view that continental orientation has influenced migration patterns and has played an important role in determining both the structure of human genetic variation and the distribution and spread of cultural traits.     

Genogeographic analysis of subdivided population. The Adyge gene pool in the Caucasian gene pool system]

A gene geographic analysis of the indigenous population of the Caucasian historical cultural province was carried out with a set of genetic markers extensively studied in the Adyges (39 alleles of 18 loci): AB0, ACP, C3, FY, GC, GLO, HP, KEL, LEW, MN, MNS, P, PGD, PGM1, RH-C, RH-D, RH-E, and TF. Genetic information on 160 Caucasian populations was used (on average, 65 populations per locus). A synthetic map of the first principal component clearly showed a division into two gene geographic provinces: Northern Caucasus and Transcaucasia. The component significantly differed across the Greater Caucasian Ridge. One of the major regions of extreme values corresponded to the Adyge region. A map of the second component revealed two poles, Northwestern (the Adyges) and Caspian, in gene pool variation of the Caucasian population. The analysis of the maps and the space of principal components showed that the Adyge population is an important component of the Caucasian gene pool. A map of genetic distance from all Caucasian populations to the Adyges showed that the north Caucasian populations (excluding the Ossetes) are the most genetically similar to the Adyges, while Georgians from the Kolkhida Valley and Azerbaijanians from the lowlands near the Caspian Sea and highland steppes are the most genetically remote from the Adyges. The genetic diversity (GST x 10(2)) of the entire Caucasian gene pool was studied. The average diversity of subpopulation within a Caucasian ethnos was GS-E = 0.81, the diversity of ethnoses within a linguistic family was GE-L = 0.83, and the diversity of linguistic families was GL-T = 0.58. The race classification of the Caucasian populations (GS-E = 0.81, GS-R = 0.80, GR-T = 0.76) proved to be more genetically informative than the linguistic one. The major parameters of the Adyges (total diversity HT = 0.364, heterozygosity HS = 0.361, and subpopulation diversity within the ethnos GS-E = 0.69) were similar to those averaged over the entire Caucasian population. A comparison with the same set of genetic markers showed that the interethnic diversity in the Caucasian region was lower than in the other north Eurasian regions (GS-E was 1.24 in the European region, 1.42 in the Ural region, 1.27 in Middle Asia, and 3.85 in Siberia).     

Mitochondrial DNA phylogeography of Acrossocheilus paradoxus (Cyprinidae) in Taiwan

Nucleotide sequences of 3' end of the cytochrome b gene, tRNA genes, D-loop control region, and the 5' end of the 12S rRNA of mitochondrial DNA (mtDNA) were used to assess the genetic and phylogeographic structure of Acrossocheilus paradoxus populations, a Cyprinidae fish of Taiwan. A hierarchical examination of populations in 12 major streams from three geographical regions using an analysis of molecular variance (AMOVA) indicates high genetic differentiation both among populations (PhiST = 0.511, P < 0.001) and among regions (PhiCT = 0.368, P < 0.001). Limited migration largely contributed to the genetic differentiation. High nucleotide diversity (1.13%) and haplotype diversity (0.80%) were detected among populations. The degree of genetic differentiation was correlated with geographical distance between populations, a result consistent with the one-dimensional stepping stone models. A neighbour-joining tree recovered by (DAMBE) supports the pattern of isolation by distance and reveals a closer relationship between populations of the central and southern regions. A minimum spanning network based on nucleotide substitutions reflected migration routes from populations of the central region to the northern and southern regions, respectively. Postglacial colonization and expansion can explain the phylogeographical pattern. Single and ancient migration events may have allowed the northern region to attain the monophyly of mtDNA alleles. In contrast, most populations within geographical regions are either paraphyletic or polyphyletic due to the relatively shorter time period for coalescence. Both low haplotype number and genetic variability suggest a bottleneck event in the Chingmei population of northern Taiwan. Based on coalescence theory, the monophyly of the Tungkang population of the southern region may be associated with a founder event.     

Migration between continents: geographical structure and long-distance gene flow in Porpidia flavicunda (lichen-forming Ascomycota)

Historical and contemporary geographical distribution ranges with their associated gene flow patterns interact to produce the genetic diversity observed today. Often it is not possible to separate out the impacts of historical events, e.g. past fragmentation, and contemporary gene flow, e.g. long-distance dispersal. Porpidia flavicunda is a lichen-forming ascomycete occurring circumpolar in the boreal to arctic zones for which vegetation history suggests that its distribution pattern has stayed broadly the same over the past millennia. DNA-sequence diversity in P. flavicunda can, thus, be expected to predominantly represent geographical population differentiation and its contemporary migration rates. The population sample consists of 110 specimens collected in Northern Québec, Baffin Island, Western Greenland and Northern Scandinavia. DNA-sequence data sets of three nuclear gene fragments (LSU, RPB2 and beta-tubulin) were analysed for genetic diversity within, and differentiation between, geographical regions. Tests of population subdivision employing analyses of molecular variance and exact tests of haplotype frequency distributions showed significant structure between the geographical regions. However, the lack of fixed nucleotide polymorphisms and the wide sharing of identical haplotypes between geographical regions suggest recurrent long-distance gene flow of propagules. Still, the means by which propagules are dispersed remain to be discovered. Inference of migration rates shows that in many cases a sufficiently high amount of migrants is exchanged between geographical regions to prevent drastic population differentiation through genetic drift. The observed haplotype distributions and migration rates point to a gene flow model of isolation by distance.     

Structure of allozyme variation in Nordic Silene nutans (Caryophyllaceae): population size, geographical position and immigration history

We investigated allozyme variation in 34 populations of the perennial herb Silene nutans from Sweden and northern Finland, areas that were ice-covered during the last (Weichselian) glaciation. The present geographical structure of genetic variation in S. nutans in Sweden and northern Finland appears to have been mainly shaped by ancient historical processes. Patterns of variation in allele frequencies suggest two major postglacial immigration routes into Sweden, with populations entering the area from both the south and the east and forming a contact zone with admixed populations in central Sweden. While estimates of within-population genetic diversity and allelic richness are significantly correlated with present population size and geographical position (latitude), population size is not correlated with latitude. Low genetic diversity in the northern populations is more likely to have resulted from ancient stochastic events during the process of immigration than from recent population fragmentation. F _IS values are high and increase with latitude. Evidence of recent bottlenecks was detected in several southern Swedish populations: these can be interpreted in terms of population fragmentation as a result of anthropogenic disturbance. Soil pH is uncorrelated with population size and position.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81 , 357–371.     

Medical genetic study of the population of Turkmenia. VI. Intrapopulation variability from an analysis of marriage migrations and ABO and Hp marker systems

By the sampling procedure, the distribution of phenotypic and genotypic frequencies of ABO and Hp systems and the structure of intermarriage migration in Turkmen population was studied. The geographical subdivision of the Turkmen population coincided with its ethnic divergency. The main Turkmen tribes are highly isolated (the gametic index is 0.965 to 1.0) and the differences in gene frequencies between tribes are significant. The mean gene frequencies for the ABO system in the Turkmen population are: I0-0.5373, IA-0.2601, IB-0.2025, these being Hp1-0.284, Hp2-0.716 for the Hp system.     

Genetic relationships among marine and freshwater populations of the European three-spined stickleback (Gasterosteus aculeatus) revealed by microsatellites

To assess the population genetic structure of the three-spined stickleback, Gasterosteus aculeatus, variability at 18 microsatellite loci was examined in 1724 individuals from 74 locations covering most of the species distribution range in Europe. The results revealed high overall degree of differentiation (F(ST) = 0.21) but contrasting level of divergence and genetic variability between habitat types. Marine populations were genetically relatively uniform even across great geographical distances as compared to substantial differentiation among freshwater populations. Analysis of molecular variance indicated low but significant (2.7%) variation in allele frequencies between geographical regions, but a negligible effect of habitat type (0.2%). The phylogenetic pattern was not explained by habitat type, but a weak signal of populations clustering according to geographical or water system origin was found. The results support the view that three-spined stickleback marine ancestors colonized northern European fresh waters during the postglacial marine submergence c. 10,000 years ago, whereas in the Mediterranean region colonization probably dates back to the Pleistocene. The independent origins of river and lake populations indicate that they originate from multiple colonizations rather than sharing common ancestry. In the continuous marine environment, the low degree of differentiation among populations can be explained by gene flow among subpopulations and large effective population size buffering divergence in neutral markers. In contrast, among postglacially established freshwater populations differentiation appears to be driven by genetic drift and isolation. The stepwise mutations appear to have contributed to the population differentiation in the southern part of the three-spined stickleback distribution range.     

Gm and Km allotypes in 74 Chinese populations: a hypothesis of the origin of the Chinese nation

Summary This paper reports the distribution of immunoglobulin Gm and Km allotypes in 74 Chinese geographical populations. These populations are derived from 24 nationalities comprising 96.6% of the total population of China. A total of 9,560 individuals were phenotyped for Gm(1,2,3,5,21) factors, and 9,611 were phenotyped for Km(1). Phylogenetic trees were constructed on the basis of Gm haplotype frequencies and genetic distances. The results of cluster analysis show the heterogeneity of the Chinese nation, and confirm the hypothesis that the modern Chinese nation originated from two distinct populations, one population originating in the Yellow River valley and the other originating in the Yangtze River valley during early neolithic times (3,000–7,000 years ago). Frequencies of the Gm haplotype of 74 Chinese populations were compared with those of 33 populations from major racial groups. The results suggest that during human evolution, the Negroid group and Caucasoid-Mongoloid group diverged first, followed by a divergence between the Caucasoid and Mongoloid. Interrace divergence is high in comparison with intrarace divergence. There appear to be two distinct subgroups of Mongoloid, northern and southern Mongoloid. The northern and southern Mongoloid have Gm^1;21 and Gm^1,3;5 haplotypes as race-associate markers, respectively. Furthermore, the Caucasian-associated haplotype Gm^3;5 was found in several of the minorities living in the northwest part of China. The presence of the Gm^3;5 haplotype is attributed to the Caucasians living in Central Asia throughout the Silk Road. The amount of Caucasian admixture has been estimated. In contrast to the Gm haplotype distribution, Km¹ gene frequencies showed a random distribution in the populations studied.     

Mitochondrial DNA evidence for high levels of gene flow among populations of a widely distributed anadromous lamprey Entosphenus tridentatus (Petromyzontidae)

Mitochondrial DNA variation among 1246 individuals of Pacific lamprey ( Entosphenus tridentatus ) from 81 populations spanning 2600 km from the Skeena River, British Columbia, to the Ventura River, California, was surveyed using five restriction enzymes. A total of 29 composite haplotypes was detected in two gene fragments (ND2 and ND5). The three most common haplotypes, occurring in 91% of all samples, were present at similar frequencies in all regions. Samples were divided into six biogeographic regions based on sample distribution and geographical landmarks to assess geographic genetic structure. Analysis of molecular variance indicated that 99% of the genetic variation was explained by variability within drainages. The lack of geographical population structure is likely related to a life-history pattern that includes a prolonged larval freshwater stage, migration to oceanic feeding and return to fresh water to spawn. The lack of strong natal homing apparently promotes gene flow among drainages and regions.     

Genetic Diversity and Population Structure of Dioscorea tokoro Makino, a Dioecious Climber

Abstract Dioscorea tokoro Makino is a herbaceous climber species widespread in East Asia. Genetic structure of a natural population of D. tokoro was examined employing starch gel electrophoresis of allozymes. Genotypes of seven loci were studied for 1,128 individuals. Twenty-six populations located mainly in the Kinki district of Japan were subgrouped into four large clusters by the geographical distribution of alleles. The D. tokoro population was revealed to contain greater total genetic diversity ( H_T =0.282) and higher intrapopulational genetic diversity ( H_S =0.258) than other outcrossing species for which data are available. On the other hand, interpopulational differentiation ( G_ST =0.096) was smaller than in other outcrossers. For the heterozygosity deficiency observed ( F_IT =0.125), population subdivision ( F_ST =0.096) and inbreeding within the population ( F_IS =0.067) were revealed to contribute to the same extent. From these F -statistics, the migration rate among subpopulations and the rate of between-relative matings were estimated. Overall results on the genetic structure of the D. tokoro population indicated a high gene flow among its subpopulations, and this may be the consequence of its life form as a climber and its habitat in a disturbed environment. During the study, the geographical cline of Pgi allele frequencies was observed. This finding was supposed to be the result of the selection imposed on Pgi by the temperature differences between localities.     

Phylogeography of the black fly Simulium tani (Diptera: Simuliidae) from Thailand as inferred from mtDNA sequences

Intraspecific phylogeography has been used widely as a tool to infer population history. However, little attention has been paid to Southeast Asia despite its importance in terms of biodiversity. Here we used the cytochrome oxidase I gene of mitochondrial DNA (mtDNA) for a phylogeographic study of 147 individuals of the black fly Simulium tani from Thailand. The mtDNA revealed high genetic differentiation between the major geographical regions of north, east and central/south Thailand. Mismatch distributions indicate population expansions during the mid-Pleistocene and the late Pleistocene suggesting that current population structure and diversity may be due in part to the species' response to Pleistocene climatic fluctuations. The genealogical structure of the haplotypes, high northern diversity and maximum-likelihood inference of historical migration rates, suggest that the eastern and central/southern populations originated from northern populations in the mid-Pleistocene. Subsequently, the eastern region had had a largely independent history but the central/southern population may be largely the result of recent (c. 100,000 years ago) expansion, either from the north again, or from a relictual population in the central region. Cytological investigation revealed that populations from the south and east have two overlapping fixed chromosomal inversions. Since these populations also share ecological characteristics it suggests that inversions are involved in ecological adaptation. In conclusion both contemporary and historical ecological conditions are playing an important role in determining population genetic structure and diversity.