Levels Of Gene Diversity Research Articles

Characteristics of microsatellite loci in Odonata

Abstract Microsatellite loci have become the genetic markers of choice for population-level molecular ecological studies. However, microsatellite loci had been isolated for comparatively few species of odonate until the past five years. This review summarises the main characteristics - expected heterozygosity and microsatellite length - of 116 microsatellite loci that have been isolated from the genomes of 11 odonate species and discusses potential problems associated with using microsatellite loci to study odonate biology. It is clear that odonates are characterised by relatively short microsatellites, typically less than 10 core motifs, that demonstrate a high level of heterozygote deficits. Some reasons why some odonate species have particularly low levels of gene diversity are discussed also.

Single sequence repeat markers reflect diversity and geographic barriers in Eurasian populations of the conifer pathogen Ceratocystis polonica

SummaryThe blue‐stain fungus and vascular stain pathogen Ceratocystis polonica and its associated bark beetle vectors, particularly Ips typographus and I. typographus japonicus, cause significant losses to several spruce species in Eurasia. Nothing is, however, known about the population genetics of this conifer pathogen. In this study, a set of single sequence repeat (SSR) markers were developed to determine the population structure and genetic diversity of C. polonica in Europe and Japan. ISSR‐PCR primers were used to target SSR‐rich regions and specific primers were designed flanking the SSR regions found in these amplicons. The SSR primers developed for C. polonica were found to be transferable to six other Ceratocystis species from conifers, residing in the Ceratocystis coerulescens complex. Ninety‐eight isolates representing four populations of C. polonica (Austria, Norway, Poland and Japan) were tested using 10 selected polymorphic SSR markers. A high level of gene diversity was found in C. polonica as a whole (H = 0.53). Analysis of G statistics showed a low degree of population structure in Europe and a high level of gene flow between populations (Gst = 0.05, Nm = 8.5). In contrast, the Japanese and the European populations of C. polonica displayed strong genetic separation, which is likely caused by geographic isolation. The low level of population structure of C. polonica in Europe and the differentiation between the European and the Japanese fungal populations mirror previous findings for I. typographus and I. typographus japonicus, the main insect vectors of this fungus. These results support the view that the fungus and the insect have closely co‐evolved together. This study also suggests that movement of C. polonica and its vectors between Europe and Asia pose a threat to forestry on both continents and this should clearly be avoided.

Genetic characteristics of hybrid populations derived by crossing Chinese and Indian pearl oysters, Pinctada fucata, based on AFLP markers

In selective breeding, hybrid populations of pearl oysters Pinctada fucata were made by crossing Indian pearl oysters with Chinese ones. Genetic characteristics of 2 hybrid populations, Indian(♀) × Sanya(♂) and Sanya(♀) × Indian(♂) and 2 pure populations, Indian × Indian and Sanya × Sanya, were investigated using AFLP markers. A total of 230 loci were generated by 3 pairs of primer combinations. Indian-Sanya hybrid showed the highest proportion of polymorphic loci (99.6%) and the largest number of dominant, monomorphic loci (38). Gene diversity was 0.422 for total, 0.364 for average, ranging from 0.360 to 0.372. The level of gene diversity in Indian-Sanya (0.372) was significantly higher than those inthe other populations (P < 0.001). Significant and high levels of overall and pairwise genetic differentiation were observed among the 4 populations as revealed by GST and AMOVA. These results suggested that both the hybrid and pure populations were characterized by high levels of genetic diversity and genetic differentiation at the beginning of selection, implying that artificial reproduction could have more impact on genetic differentiation than on genetic diversity at the first stage of selective breeding. Yet the high level of genetic divergence among populations suggested that monitoring changes of genetic variation of selected strains is necessary and critical for rational management of brood stocks in selective breeding practice. Key words: AFLP, gene diversity, genetic differentiation, pearl oyster, hybrid population.

Population genetic structure of Sclerotinia sclerotiorum on canola in Iran

The genetic structure of 276 Sclerotinia sclerotiorum isolates representing 37 field populations from four provinces in northern Iran were analysed with six polymorphic microsatellite loci. In total, 80 haplotypes were detected with 19 haplotypes (23.7%) shared amongst at least two regional populations. None of the haplotypes were shared among all four regional populations. Of the 80 haplotypes, 32 haplotypes (40%) occurred in low frequencies represented by only one isolate. Moderate levels of gene diversity (H = 0.51 to 0.61) and genotypic diversity (Ĝ = 12.0 to 22.0; clonal fraction = 0.39 to 0.67) for regional populations were observed. Genotypic diversities (Ĝ) did not differ significantly among populations. All regional populations were in linkage equilibrium indicating the occurrence of outcrossing. Low to moderate levels of population subdivision (0.03 to 0.07), were observed among regional populations. Only one large panmictic population was inferred by Structure, indicating no significant population structure. A Mantel test showed no significant isolation by distance (r = −0.43; P = 0.18), indicating anthropogenic movement of inoculum. The results demonstrated that S. sclerotiorum populations in northern Iran, are randomly mating and have a number of shared haplotypes among regional populations; this possibly represents recent founder populations and/or a high occurrence of anthropogenic migration of infected plant material among populations.

Genic variation at sex-linked loci: quantification of regular selection models.

The level and determinants of genic variation were studied under the following regular selection models: (A) overdominance with identical selection in the sexes, and (B) codominance and (C) dominance with opposite selection in the sexes. In each model, the portion of the fitness space leading to stable allele frequency equilibrium is smaller at sex-linked loci than at autosomal ones. With most fitness values, also the level of gene diversity at equilibrium is lower at sex-linked loci. The models can also be applied to haplodiploid populations. The bearing of the results on social evolution of the Hymenoptera is discussed.

Genetic Variation in the Endangered Astragalus jaegerianus (Fabaceae, Papilionoideae): A Geographically Restricted Species

Abstract Knowledge of genetic variation and population structure is critically important in the conservation of endangered species. The level and partitioning of genetic variation in the narrow endemic Astragalus jaegerianus was investigated using DNA sequence data and AFLP markers. The DNA sequence data for the cpDNA trnL-F and nrDNA ITS regions were monomorphic for A. jaegerianus but polymorphic for two congeners, which suggest A. jaegerianus is genetically depauperate. On the other hand, the genome-wide survey using AFLP markers revealed substantial gene diversity (0.2660) and significant population structure (global FST = 0.133, p < 0.01). This level of gene diversity and its partitioning among populations is comparable to patterns for geographically widespread species. These findings also challenge the hypothesis that levels of gene diversity are best predicted by population size. In this case, levels of gene diversity within populations are significantly correlated with population density, while g...

METAPOP—A software for the management and analysis of subdivided populations in conservation programs

We introduce a computer program for the dynamic and flexible management of conserved subdivided populations. Using molecular marker data or pedigree information, the software determines the optimal contributions (i.e., number of offspring) of each individual, the number of migrants, and the particular subpopulations involved in the exchange of individuals in order to maintain the largest level of gene diversity in the whole population with a desired control in the rate of inbreeding. Restrictions can be introduced for the total number of migrants, and the mating of particular pairs and their contribution. A full genetic diversity analysis of the population is carried out. The optimal contribution from each subpopulation to a pool of maximal gene diversity is also provided by the program.

The evolution of pheromonal communication

Small-brained rodents have been the principle focus for pheromonal research and have provided comprehensive insights into the chemosensory mechanisms that underpin pheromonal communication and the hugely important roles that pheromones play in behavioural regulation. However, pheromonal communication does not start or end with the mouse and the rat, and work in amphibians reveals much about the likely evolutionary origins of the chemosensory systems that mediate pheromonal effects. The dual olfactory organs (the main olfactory epithelium and the vomeronasal organ), their receptors and their separate projection pathways appear to have ancient evolutionary origins, appearing in the aquatic ancestors of all tetrapods during the Devonian period and so pre-dating the transition to land. While the vomeronasal organ has long been considered an exclusively pheromonal organ, accumulating evidence indicates that it is not the sole channel for the transduction of pheromonal information and that both olfactory systems have been co-opted for the detection of different pheromone signals over the course of evolution. This has also led to great diversity in the vomeronasal and olfactory receptor families, with enormous levels of gene diversity and inactivation of genes in different species. Finally, the evolution of trichromacy as well as huge increases in social complexity have minimised the role of pheromones in the lives of primates, leading to the total inactivation of the vomeronasal system in catarrhine primates while the brain increased in size and behaviour became emancipated from hormonal regulation.

Temporal Trends of Variation in Italian Rice Germplasm over the Past Two Centuries Revealed by AFLP and SSR Markers

The aim of this study was to characterize the Italian rice (Oryza sativa L.) gene pool, paying particular attention to its variation over time, to determine whether human activity can reduce genetic variability, and whether such a reduction actually occurred in Italian rice varieties. We analyzed 135 Italian rice accessions, representing genotypes either introduced from abroad or developed in Italy from 1880 to 2001, using two groups of molecular markers, amplified fragment length polymorphisms and simple sequence repeats. These accessions were divided into four groups for which different statistical analyses were performed. The levels of gene diversity, from 0.1023 to 0.1921, and genetic richness, from 0.1579 to 0.3064, increased over time. Genetic structure, as estimated by analysis of molecular variance, revealed that the within‐component was overwhelmingly dominant (92%) compared with the among‐component. These results show that the level of genetic diversity in Italian rice accessions has remained high since 1850 and continues to increase. This is most likely the result of Italian breeding programs that developed new cultivars and introduced others from abroad, without substituting previous accessions. Our results show that the management and improvement of rice germplasm in Italy have been successful in maintaining sufficient genetic diversity.

Genetic structure of an insect-pollinated and bird-dispersed tropical tree in vegetation fragments and corridors: implications for conservation

In the vegetation corridors that connect small remnants of undisturbed primary forest in the Lavras landscape (Brazil), Protium spruceanum is a representative of a mass-flowering insect-pollinated and bird-dispersed tree. Allozyme variation was quantified from five forest remnants (N = 150) from secondary vegetation corridors linking them (N = 80) to generate information for genetic conservation. The species adhered to H-W equilibrium in all fragments in most of the loci. The results indicated high gene diversity in the fragments $$({\hat{H}}_{\rm e}=0.381{-}0.507)$$ and corridors $$({\hat{H}}_{\rm e}=0.336{-}0.470),$$ positively correlated with the plant density (r = 0.742, R 2 = 0.551, d.f. = 4). We did not find evidence of inbreeding within fragments $$(\hat{f}=-0.188, P<0.05)$$ nor overall $$(\hat{F}=-0.101, P<0.05).$$ The genetic differentiation among remnants was low $$(\hat{\theta}_{\rm p}=2.8\%).$$ Evidence of recent bottlenecks by anthropogenic disturbance was detected in fragments (P < 0.05, Wilcoxon sign-rank test). The minimal viable population was estimated for conservation in situ, indicating fragments with possibilities of maintaining genetic equilibrium diversity in the short term (except F3) and in the long term (only F5). The $$\hat{N}_{\rm e}/N$$ ratios was also calculated to contribute to vegetation enrichment, area recovery or creation of new vegetation corridors. We found high levels of gene diversity in the vegetation corridors, genetic identity with the fragments and absence of inbreeding. Thus, our results suggest that landscape management strategies should therefore consider both the creation of new vegetation corridors and the protection of extant ones.

Genetic diversity and structure of farm and GenBank accessions of cacao (Theobroma cacao L.) in Cameroon revealed by microsatellite markers

The genetic diversity of 400 accessions collected in cacao farms, 95 GenBank, and 31 reference accessions was analyzed using the 12 microsatellite markers. The GenBank and reference accessions were subdivided into 12 accession groups (AG) that belong to the traditional cacao genetic groups (GG) Lower Amazon Forastero (LA), Upper Amazon Forastero (UA), Trinitario, and Criollo (Cr). The 12-microsatellite loci revealed a total of 125 alleles, 113 of which were present in the farm accession group (FA). The within and between group variation for all AGs accounted respectively for 81% and 19% of the total molecular variation. The average Fis for the FA was 0.15 suggesting a moderate level of inbreeding. Significant differences for the level of gene diversity were found between the farm (0.50), GenBank (0.42 to 0.62), and reference (0.10 to 0.60) AGs. Genetic differentiation among AGs was variable with Fst values varying between 0.14 and 0.57 for the different AGs. Analysis using a Bayesian model-based method showed the existence of a high level of admixture for the farm accessions group. The LA genes were most represented in the FA (54%), followed by UA (33%) and Cr (7%). The genes of LA were also the most represented in the GenBank (48%), followed by UA (24%) and Cr (14%). Only 14% and 6% of the genes of the GenBank and farm accessions, respectively, could not be attributed to any of the reference GGs. The results suggest the predominating presence of LA genes in the Cameroon farm accessions and a high level of admixture, with apparent presence of genes of more than three GGs in most accessions. The traditional Trinitario types appear to have almost disappeared from farmers fields. The admixture must be the result of hybridization and recombination of these genes from the different GGs in seed gardens and in farmers’ fields. The use of selected farm accessions will depend on the GG that it belongs to and also on their level of heterozygosity. Further implications of the results for breeding and for introduction of new germplasm into the Cameroon GenBank are discussed.

Microsatellite diversity and genetic structure of the commercially important tropical tree species Eucalyptus urophylla, endemic to seven islands in eastern Indonesia

Eucalyptus urophylla (Timor mountain gum) is an economically important plantation species that occurs naturally in a series of disjunct populations on the volcanic slopes of seven islands in eastern Indonesia. Twelve microsatellite markers were used to investigate the distribution of nuclear genetic diversity among 19 geographically defined E. urophylla populations. High levels of gene diversity were observed throughout the geographic range (H E = 0.703 to 0.776). The level of genetic differentiation among populations was low (F ST = 0.031), but the amount of differentiation increased with geographic distance. A phenogram produced by a neighbor-joining analysis illustrated that populations clustered according to islands. However, a Bayesian clustering approach revealed a more cryptic population structure comprising two genetically homogeneous groups. Gene flow among the populations is likely responsible for the apparent weak influence of geographic insularity on the genetic diversity and structure of the island species. These findings provide direction for conservation and breeding strategies in E. urophylla.

Evolutionary history of the endangered fish Zoogoneticus quitzeoensis (Bean, 1898) (Cyprinodontiformes: Goodeidae) using a sequential approach to phylogeography based on mitochondrial and nuclear DNA data

BackgroundTectonic, volcanic and climatic events that produce changes in hydrographic systems are the main causes of diversification and speciation of freshwater fishes. Elucidate the evolutionary history of freshwater fishes permits to infer theories on the biotic and geological evolution of a region, which can further be applied to understand processes of population divergence, speciation and for conservation purposes. The freshwater ecosystems in Central Mexico are characterized by their genesis dynamism, destruction, and compartmentalization induced by intense geologic activity and climatic changes since the early Miocene. The endangered goodeid Zoogoneticus quitzeoensis is widely distributed across Central México, thus making it a good model for phylogeographic analyses in this area.ResultsWe addressed the phylogeography, evolutionary history and genetic structure of populations of Z. quitzeoensis through a sequential approach, based on both microsatellite and mitochondrial cytochrome b sequences. Most haplotypes were private to particular locations. All the populations analysed showed a remarkable number of haplotypes. The level of gene diversity within populations was d = 0.987 (0.714 – 1.00). However, in general the nucleotide diversity was low, π = 0.0173 (0.0015 – 0.0049). Significant genetic structure was found among populations at the mitochondrial and nuclear level (ΦST = 0.836 and FST = 0.262, respectively). We distinguished two well-defined mitochondrial lineages that were separated ca. 3.3 million years ago (Mya). The time since expansion was ca. 1.5 × 106 years ago for Lineage I and ca. 860,000 years ago for Lineage II. Also, genetic patterns of differentiation, between and within lineages, are described at different historical timescales.ConclusionOur mtDNA data indicates that the evolution of the different genetic groups is more related to ancient geological and climatic events (Middle Pliocene, ca. 3.3 Mya) than to the current hydrographic configuration of the basins. In general, mitochondrial and nuclear data supported the same relationships between populations, with the exception of some reduced populations in highly polluted basins (Lower Lerma River), where the effects of genetic drift are suggested by the different analyses at the nuclear and mitochondrial level. Further, our findings are of special interest for the conservation of this endangered species.

Genetic diversity and admixture analysis of Sanfratellano and three other Italian horse breeds assessed by microsatellite markers

Sanfratellano is a native Sicilian horse breed, mainly reared in the north east of the Island, developed in the 19th century from local dams and sires with a restricted introgression of Oriental, African and, more recently, Maremmano stallions. In this study, the genetic relationships and admixture among Sanfratellano, the other two Sicilian autochthonous breeds and Maremmano breed were assessed using a set of microsatellites. The main goals were to infer the impact of Maremmano breed in the current Sanfratellano horse and to provide genetic information useful to improve the selection strategies of the Sanfratellano horse. The whole sample included 384 horses (238 Sanfratellano, 50 Sicilian Oriental Purebred, 30 Sicilian Indigenous and 66 Maremmano), chosen avoiding closely related animals. A total of 111 alleles from 11 microsatellite loci were detected, from four at HTG7 to 15 at ASB2 locus. The mean number of alleles was the lowest in Oriental Purebred (6.7), the highest in Sanfratellano (8.3). All the breeds showed a high level of gene diversity (He) ranging from 0.71 ± 0.04 in Sicilian Oriental Purebred to 0.81 ± 0.02 in Sicilian Indigenous. The genetic differentiation index was low; only about 6% of the diversity was found among breeds. Nei’s standards (DS) and Reynolds’ (DR) genetic distances reproduced the same population ranking. Individual genetic distances and admixture analysis revealed that: (a) nowadays Maremmano breed does not significantly influence the current Sanfratellano breed; (b) within Sanfratellano breed, it is possible to distinguish two well-defined groups with different proportions of Indigenous blood.

Genetic diversity in diploid vs. tetraploid Rorippa amphibia (Brassicaceae)

The frequency of polyploidy increases with latitude in the Northern Hemisphere, especially in deglaciated, recently colonized areas. The cause or causes of this pattern are largely unknown, but a greater genetic diversity of individual polyploid plants due to a doubled genome and/or a hybrid origin is seen as a likely factor underlying selective advantages related to life in extreme climates and/or colonization ability. A history of colonization in itself, as well as a recent origin, and possibly a limited number of polyploidization events would all predict less genetic diversity in polyploids than in diploids. The null hypothesis of higher gene diversity in polyploids has to date hardly been quantified and is here tested in self-incompatible Rorippa amphibia (Brassicaceae). The species occurs in diploid and tetraploid forms and displays clear geographical polyploidy in Europe. On the basis of eight microsatellite loci it can be concluded that the level of gene diversity is higher in tetraploids than in diploids, to an extent that is expected under neutral evolution when taking into account the larger effective population size in the doubled cytotype. There is thus no evidence for reduced genetic diversity in the tetraploids. The evidence presented here may mean that the tetraploids' origin is not recent, has not been affected by bottlenecks and/or that tetraploids were formed multiple times while an effect of introgression may also play a role.

The dynamic of the t-haplotype in wild populations of the house mouse Mus musculus domesticus in Israel

The t-haplotype, a variant of the proximal part of the mouse chromosome 17, is composed of at least four inversions and is inherited as a single genetic unit. The haplotype causes embryonic mortality or male sterility when homozygous. Genes within the complex are responsible for distortion of Mendelian transmission ratio in males. Thus, the t-haplotype in heterozygous males is transferred to over 95% of the progeny. We examined the dynamic and behavior of the t-haplotype in wild populations of the house mouse in Israel. The Israeli populations show high frequency (15%-20%) of both partial and complete t-carrying mice, supporting the suggestion that the t-complex evolved in the M. domesticus line in the Israeli region. In one population that had the highest frequency of t-carrying individuals, we compared the level of gene diversity between t-carrying and normal mice in the marker's loci: H-2 locus of the major histocompatibility complex (MHC) on the t-haplotype of chromosome 17, three microsatellites on other chromosomes, and the mitochondrial D-loop. Genetic variability was high in all tested loci in both t and (+) mice. All t mice carried the same chromosome and showed the same H-2 haplotype. While t-carrying mice showed significant H-2 heterozygotes access, (+) mice expressed significant H-2 heterozygote deficiency. There were no differences in the level of gene diversity between t and (+) mice in the other loci. Heterozygosity level at the MHC may be an additional factor in the selective forces balancing the t-haplotype polymorphism.

Impact of selective logging on inbreeding and gene dispersal in an Amazonian tree population of Carapa guianensis Aubl.

Selective logging may impact patterns of genetic diversity within populations of harvested forest tree species by increasing distances separating conspecific trees, and modifying physical and biotic features of the forest habitat. We measured levels of gene diversity, inbreeding, pollen dispersal and spatial genetic structure (SGS) of an Amazonian insect-pollinated Carapa guianensis population before and after commercial selective logging. Similar levels of gene diversity and allelic richness were found before and after logging in both the adult and the seed generations. Pre- and post-harvest outcrossing rates were high, and not significantly different from one another. We found no significant levels of biparental inbreeding either before or after logging. Low levels of pollen pool differentiation were found, and the pre- vs. post-harvest difference was not significant. Pollen dispersal distance estimates averaged between 75 m and 265 m before logging, and between 76 m and 268 m after logging, depending on the value of tree density and the dispersal model used. There were weak and similar levels of differentiation of allele frequencies in the adults and in the pollen pool, before and after logging occurred, as well as weak and similar pre- and post-harvest levels of SGS among adult trees. The large neighbourhood sizes estimated suggest high historical levels of gene flow. Overall our results indicate that there is no clear short-term genetic impact of selective logging on this population of C. guianensis.

Development of microsatellites for the peat moss Sphagnum capillifolium using ISSR cloning

AbstractSphagnum mosses are major components of peat bogs but populations of many species are under threat due to habitat fragmentation resulting from the cutting of peat for fuel. We have used an intersimple sequence repeat (ISSR)‐based cloning method to develop nine polymorphic nuclear microsatellites for the peat moss species Sphagnum capillifolium. Between three and seven alleles per locus were detected in a sample of 48 haploid gametophytes and levels of gene diversity ranged from 0.5391 to 0.7960. These represent the first microsatellite markers developed for this important genus and most also exhibited cross‐species amplification across a range of common Sphagnum species.

Assessment of EST-microsatellites markers for discrimination and genetic diversity in bread and durum wheat landraces from Afghanistan

Accurate and reliable means for identification are necessary to assess the discrimination between landraces of tetraploid wheat [T.␣turgidum L. subsp. durum (Desf.) Husn.] and hexaploid wheat (T. aestivum L. em. Thell.). In Afghanistan, farmers usually cultivate mixed landraces, and thus distinction between bread and durum is difficult. A set of 18 microsatellites derived from the DuPont EST-database were used to describe genetic diversity in a sample of 82 Afghan wheat landraces. A total of 101 alleles were detected, with allele number per locus ranging from 2 to 13, and a mean allele number of 6.31. The percentage of polymorphic loci was 89%. The EST-SSRs markers showed different level of gene diversity: the highest Polymorphism Information Content value (0.921) was observed with DuPw 221. Our results demonstrated that with a reasonable number of expressed sequences target microsatellites (EST-SSRs) it is possible to discriminate between T. durum and T. aestivum species of wheat germplasm. Our results showed that EST-databases could be a useful source for species-specific markers and have the potential for new genic microsatellites markers that could enhance screening germplasm in gene banks.

Postglacial-period and Recent Invasions Shape the Population Genetics of Botryllid Ascidians along European Atlantic Coasts

The colonial urochordate Botryllus schlosseri is a sedentary species of Mediterranean origin that became cosmopolitan, probably because of postglacial-period dispersal and human-mediated invasions of colonies attached to ship hulls. Here we studied microsatellite allele diversity of Atlantic coast populations from an area ranging from European regions south of the last glacial front to regions that had been permanently ice-covered. Gene diversity levels varied dramatically among populations residing in areas subject to different glacial conditions. Five populations from the Iberian Peninsula, in an area south of the last glacial front, as well as two populations from presumed refugia in Brittany, expressed high gene diversity values (expected heterozygosity [He]: 0.76–0.80; average number of alleles per locus [A]: 7.25–8.75). Two populations inhabiting areas that experienced permafrost conditions (Helgoland Island, Germany, and Plymouth, England) had intermediate values (He: 0.40–0.42; A: 3.0–4.0), whereas the Auchenmalg, Scotland, population, from an area previously covered by ice, showed a remarkably low value (He: 0.17; A: 1.75). Therefore, most European populations of B. schlosseri mirrored the movement of the ice front in the last ice age. A second population from the area that was covered by permanent ice (Lossiemouth, Scotland), however, had a high He of 0.61 and an intermediate A of 3.67. Results were compared with recent invasions (populations less than 200 years old) in the United States and New Zealand that had a higher degree of genetic variation than the European native populations established thousands of years ago. Given the overall dearth of studies on this subject, we suggest that in contemporary established Botryllus populations, gene diversity is affected by ecological factors, some of which can be traced directly to the last ice age. Other parameters of gene diversity are influenced by selection pressure, which might be more intense in northern regions.