African DNA lineages in mitochondrial gene pool of Europeans

Mitochondrial DNA (mtDNA) nucleotide sequences of African origin have been found at low frequency (1%, in average) in different European populations. In the present study, data on mtDNA variability in populations of Eurasia and Africa are analyzed and search of African-specific lineages present in Europeans is conducted. The results of analysis indicate that, despite a high diversity of African mtDNA haplotypes found in Europeans, monophyletic clusters of African mtDNA lineages, arisen in Europe and characterized by long-term diversity, are nearly absent in Europe. Only two respective clusters (belonging to haplogroups L1b and L3b), which evolutionary age does not exceed 6.5 thousands years, were revealed. Comparative analysis of distribution of frequencies of autosomal microsatellite alleles found in Russian individuals, carrying the African-specific mitochondrial haplotypes, in populations of Europe and Africa has indicated that autosomal genotypes of those Russian individuals are characterized by the presence of alleles characteristic mostly for Europeans.     

Mitochondrial diversity in European and Chinese pigs is consistent with population expansions that occurred prior to domestication

Mitochondrial DNA (mtDNA) diversity in European and Asian pigs was assessed using 1536 samples representing 45 European and 21 Chinese breeds. Diagnostic nucleotide differences in the cytochrome b (Cytb) gene between the European and Asian mtDNA variants were determined by pyrosequencing as a rapid screening method. Subsequently, 637bp of the hypervariable control region was sequenced to further characterize mtDNA diversity. All sequences belonged to the D1 and D2 clusters of pig mtDNA originating from ancestral wild boar populations in Europe and Asia, respectively. The average frequency of Asian mtDNA haplotypes was 29% across European breeds, but varied from 0 to 100% within individual breeds. A neighbour-joining (NJ) tree of control region sequences showed that European and Asian haplotypes form distinct clusters consistent with the independent domestication of pigs in Asia and Europe. The Asian haplotypes found in the European pigs were identical or closely related to those found in domestic pigs from Southeast China. The star-like pattern detected by network analysis for both the European and Asian haplotypes was consistent with a previous demographic expansion. Mismatch analysis supported this notion and suggested that the expansion was initiated before domestication.     

Mitochondrial DNA phylogeography of the three-spined stickleback (Gasterosteus aculeatus) in Europe-evidence for multiple glacial refugia

An analysis of mitochondrial DNA sequence variation in 172 three-spined sticklebacks (Gasterosteus aculeatus) sampled across the European distribution range revealed three major evolutionary lineages occupying relatively large and separate geographic areas. The trans-Atlantic lineage comprised of populations spanning from the East Coast of USA to the continental Europe and was basal group to the other European lineages in the phylogeny. The European lineage included populations located in the Western and Eastern Europe, British Isles, Scandinavia as well as some parts of the Mediterranean region. The third lineage was specific to the Black Sea drainages. The within lineage structure was characterized by significant excess of low frequency haplotypes and star-like mtDNA genealogies, which suggest a recent population expansions to the formerly glaciated marine and freshwater environments. A coalescent-based method dated the splits between the major lineages to have occurred during the Saalian and Weichselian glaciations in the late Pleistocene, depending on the molecular clock calibration. The coalescent simulations further indicate high degree of genetic diversity within the lineages and a substantial increase in the genetic diversity in the European lineage relative to the ancestral level. In addition to the three major lineages, the freshwater populations in R. Neretva and L. Skadar in the Adriatic Sea coast region harboured unique and highly divergent haplotypes suggesting long independent histories of these populations. Evidence from mtDNA analyses suggests that these populations deserve a status of an evolutionary significant unit.     

Speciation and paraphyly in western mediterranean hares (Lepus castroviejoi,L. europaeus,L. granatensis,andL. capensis) revealed by mitochondrial DNA phylogeny

Mitochondrial DNA (mtDNA) variation among specimens of the northwestern African hare (Lepus capensis schlumbergeri) and three European hares sampled in Spain (L. castroviejoi andL. granatensis, which are endemic to the Iberian Peninsula, andL. europaeus) was analyzed using seven restriction endonucleases. Fourteen haplotypes were found among the 34 animals examined. Restriction site maps were constructed and the phylogeny of the haplotypes was inferred. mtDNA ofL. capensis was the most divergent, which is consistent with its allopatric African distribution and with an African origin of European hares. We estimated that mtDNA in hares diverges at a rate of 1.5–1.8% per MY assuming that the European and African populations separated 5–6 MYBP. Maximum intraspecies nucleotide divergences were 1.3% inL. capensis, 2.7% inL. castroviejoi, and 2.3% inL. granatensis but 13.0% inL. europaeus. The latter species contained two main mtDNA lineages, one on the branch leading toL. castroviejoi and the other on that leading toL. granatensis. The separation of these two lineages from theL. castroviejoi orL. granatensis lineages appears to be much older than the first paleontological record ofL. europaeus in the Iberian peninsula. This suggests that the apparent polyphyly ofL. europaeus is due not to secondary introgression, but to the retention of ancestral polymorphism inL. europaeus. The results suggest thatL. europaeus either has evolved as a very large population for a long time or has been fractionated. Such a pattern of persistence of very divergent lineages has also been reported in other species of highly mobile terrestrial mammals. As far as mtDNA is concerned,L. europaeus appears to be the common phylogenetic trunk which has diversified during dispersion over the European continent and from whichL. castroviejoi andL. granatensis speciated separately in southwest Europe.     

Genetic diversity and linkage disequilibrium in the Polynesian population of Niue Island

Isolated populations that recently have been derived from small homogeneous groups of founders should have low genetic diversity and high levels of linkage disequilibrium and should be ideal for mapping ancestral polymorphisms that influence complex genetic disease susceptibility. Populations that fulfill these criteria have been difficult to identify. We have been looking for Polynesian populations with these characteristics, because Polynesians have high rates of complex genetic diseases. In Niue Islanders all ancestral female (mitochondrial HSVI sequence) and 90.4% of ancestral male (Y-chromosome haplogroup) lineages are of Southeast Asian origin. The frequency of European Y-chromosome haplogroups is 7.2%. The diversities of mitochondrial HSV1 sequences (h = 0.18 +/- 0.05) and Y-chromosome haplo-groups (h = 0.18 +/- 0.05) are lower than values published for any other population. Ten autosomal microsatellites spaced over 5.8 cM show low allele numbers in Niue Islanders relative to Europeans (55 vs. 88 total alleles, respectively) and a modest reduction in heterozygous loci (0.71 +/- 0.02 vs. 0.78 +/- 0.02, p = 0.04). The higher linkage disequilibrium (d2) between these loci in Niue Islanders relative to Europeans (p = 0.001) is negatively correlated (r = -0.47, p = 0.01) with genetic distance. In summary, Niue Islanders are genetically isolated and have a homogeneous Southeast Asian ancestry. They have reduced autosomal genetic diversity and high levels of linkage disequilibrium that are consistent with the influence of genetic drift mechanisms, such as a founder effect or bottlenecks. High-powered linkage disequilibrium studies designed to map ancestral polymorphisms that influence complex genetic disease susceptibility may be feasible in this population.     

Evaluation of Group Genetic Ancestry of Populations from Philadelphia and Dakar in the Context of Sex-Biased Admixture in the Americas

Background

Population history can be reflected in group genetic ancestry, where genomic variation captured by the mitochondrial DNA (mtDNA) and non-recombining portion of the Y chromosome (NRY) can separate female- and male-specific admixture processes. Genetic ancestry may influence genetic association studies due to differences in individual admixture within recently admixed populations like African Americans.

Principal Findings

We evaluated the genetic ancestry of Senegalese as well as European Americans and African Americans from Philadelphia. Senegalese mtDNA consisted of ∼12% U haplotypes (U6 and U5b1b haplotypes, common in North Africa) while the NRY haplotypes belonged solely to haplogroup E. In Philadelphia, we observed varying degrees of admixture. While African Americans have 9–10% mtDNAs and ∼31% NRYs of European origin, these results are not mirrored in the mtDNA/NRY pools of European Americans: they have less than 7% mtDNAs and less than 2% NRYs from non-European sources. Additionally, there is <2% Native American contribution to Philadelphian African American ancestry and the admixture from combined mtDNA/NRY estimates is consistent with the admixture derived from autosomal genetic data. To further dissect these estimates, we have analyzed our samples in the context of different demographic groups in the Americas.

Conclusions

We found that sex-biased admixture in African-derived populations is present throughout the Americas, with continual influence of European males, while Native American females contribute mainly to populations of the Caribbean and South America. The high non-European female contribution to the pool of European-derived populations is consistently characteristic of Iberian colonization. These data suggest that genomic data correlate well with historical records of colonization in the Americas.     

Geographical patterns of mitochondrial DNA variation in Apis mellifera iberiensis (Hymenoptera: Apidae)

An extensive survey of mitochondrial haplotypes in honeybee colonies from the Iberian Peninsula has corroborated previous hypotheses about the existence of a joint clinal variation of African (A) and west European (M) evolutionary lineages. It has been found that the Iberian Peninsula is the European region with the highest haplotype diversity (12 haplotypes detected of the M lineage and 10 of the A lineage). The frequency of A haplotypes decreases in a SW-NE trend, while that of M haplotypes increases. These results are discussed in relation to hypotheses about the African origin of Apis mellifera and an early colonization of west Europe during intermediate Pleistocene glaciation events, followed by a regional differentiation. The extant pattern of haplotype frequency and distribution seems to be influenced at a regional scale by adaptation to local climatic conditions and the mobile beekeeping that has become a large-scale practice during the last decades. Other previous anthropogenic influences (Greek, Roman and Arab colonizations) are thought to be of minor importance in present day populations.     

Mitochondrial DNA sequence variation in Greeks.

Mitochondrial DNA (mtDNA) control region sequences were determined in 54 unrelated Greeks, coming from different regions in Greece, for both segments HVR-I and HVR-II. Fifty-two different mtDNA haplotypes were revealed, one of which was shared by three individuals. A very low heterogeneity was found among Greek regions. No one cluster of lineages was specific to individuals coming from a certain region. The average pairwise difference distribution showed a value of 7.599. The data were compared with that for other European or neighbor populations (British, French, Germans, Tuscans, Bulgarians, and Turks). The genetic trees that were constructed revealed homogeneity between Europeans. Median networks revealed that most of the Greek mtDNA haplotypes are clustered to the five known haplogroups and that a number of haplotypes are shared among Greeks and other European and Near Eastern populations.     

Estimates of African, European and Native American ancestry in Afro-Caribbean men on the island of Tobago

BACKGROUND/AIMS: The Tobago Afro-Caribbean population is a valuable resource for studying the genetics of diseases that show significant differences in prevalence between populations of African descent and populations of other ancestries. Empirical confirmation of low European and Native American admixture may help in clarifying the ethnic variation in risk for such diseases. We hypothesize that the degree of European and Native American admixture in the Tobago population is low. METHODS: Admixture was estimated in a random sample of 220 men, from a population-based prostate cancer screening survey of 3,082 Tobago males, aged 40 to 79 years. We used a set of six autosomal markers with large allele frequency differences between the major ethnic populations involved in the admixture process, Europeans, Native Americans and West Africans. RESULTS: The ancestral proportions of Tobago population are estimated as 94.0+/-1.2% African, 4.6+/-3.4% European and 1.4+/-3.6% Native American. CONCLUSIONS: We conclude that Tobago Afro-Caribbean men are predominantly of West African ancestry, with minimal European and Native American admixture. The Tobago population, thus, may carry a higher burden of high-risk alleles of African origin for certain diseases than the more admixed African-American population. Conversely, this population may benefit from a higher prevalence of protective alleles of African origin.     

Origins and affinities of modern humans: a comparison of mitochondrial and nuclear genetic data.

To test hypotheses about the origin of modern humans, we analyzed mtDNA sequences, 30 nuclear restriction-site polymorphisms (RSPs), and 30 tetranucleotide short tandem repeat (STR) polymorphisms in 243 Africans, Asians, and Europeans. An evolutionary tree based on mtDNA displays deep African branches, indicating greater genetic diversity for African populations. This finding, which is consistent with previous mtDNA analyses, has been interpreted as evidence for an African origin of modern humans. Both sets of nuclear polymorphisms, as well as a third set of trinucleotide polymorphisms, are highly consistent with one another but fail to show deep branches for African populations. These results, which represent the first direct comparison of mtDNA and nuclear genetic data in major continental populations, undermine the genetic evidence for an African origin of modern humans.     

Molecular Analysis Using Mitochondrial DNA and Microsatellites to Infer the Formation Process of Japanese Native Horse Populations

To assess the genetic diversity of Japanese native horse populations, we examined seven such populations using mitochondrial DNA (mtDNA) and microsatellite analyses. Four reference populations of Mongolian horses and European breeds were employed as other equids. In the mtDNA analysis, the control region (D-loop) of 411 bp was sequenced, and 12 haplotypes with 33 variable sites were identified in the Japanese native horses. The phylogenetic tree constructed by haplogrouping and using worldwide geographic references indicated that the haplotypes of the Japanese native horses were derived from six equid clusters. Compared with the foreign populations, the Japanese native populations showed lower within-population diversity and higher between-population differentiation. Microsatellite analysis, using 27 markers, found an average number of alleles per locus of 9.6 in 318 native and foreign horses. In most native populations, the within-population diversity was lower than that observed in foreign populations. The genetic distance matrix based on allelic frequency indicated that several native populations had notably high between-population differentiation. The molecular coancestry-based genetic distance matrix revealed that the European populations were differentiated from the Japanese and Mongolian populations, and no clear groups could be identified among the Japanese native horse populations. The genetic distance matrices had few correlations with the geographic distribution of the Japanese native populations. Based on the results of both mtDNA and microsatellite analyses, it could be speculated that each native population was formed by the founder populations derived from Mongolian horses. The genetic construction of each population appears to have been derived from independent breeding in each local area since the time of population fission, and this was accompanied by drastic genetic drift in recent times. This information will help to elucidate the ancestry of Japanese native horses. An erratum to this article can be found at     

Genetic structure and distinctness of Apis mellifera L. populations from the Canary Islands

The genetic structure of Apis mellifera populations from the Canary Islands has been assessed by mitochondrial (restriction fragment length polymorphisms of the intergenic transfer RNAleu-COII region) and nuclear (microsatellites) studies. These populations show a low level of genetic variation in terms of average number of alleles and degree of heterozygosity. Significant differences in the distribution of alleles were found in both data sets, confirming the genetic differentiation among some of the islands but not within them. Two mitochondrial haplotypes characteristic of the Canary Islands are found at high frequencies, although populations are introgressed by imported honeybees of eastern European C lineage. This introgression is rather high on Tenerife and El Hierro and low on Gran Canaria and La Gomera, whereas on La Palma it has not been recorded. The finding of microsatellite alleles characteristic of the eastern European lineage corroborates the genetic introgression. Phylogenetic analyses indicate that the Canarian honeybees are differentiated from other lineages and provide genetic evidence of their African origin.     

Structural analysis of insulin minisatellite alleles reveals unusually large differences in diversity between Africans and non-Africans

The insulin minisatellite (INS VNTR) associates with susceptibility to a variety of diseases. We have developed a high-resolution system for analyzing variant repeat distributions applicable to all known minisatellite alleles, irrespective of size, which allows lineages of related alleles to be identified. This system has previously revealed extremely low structural diversity in the minisatellite among northern Europeans from the United Kingdom, with all alleles belonging to one of only three highly diverged lineages called "I," "IIIA," and "IIIB." To explore the origins of this remarkably limited lineage diversity, we have characterized an additional 780 alleles from three non-African and three African populations. In total, 22 highly diverged lineages were identified, with structural intermediates absent from extant populations, suggesting a bottleneck within the ancestry of all humans. The difference between levels of diversity in Africans and non-Africans is unusually large, with all 22 lineages identified in Africa compared with only three lineages seen not only in the United Kingdom but also in the other non-African populations. We also find evidence for overrepresentation of lineage I chromosomes in non-Africans. These data are consistent with a common out-of-Africa origin and an unusually tight bottleneck within the ancestry of all non-African populations, possibly combined with differential and positive selection for lineage I alleles in non-Africans. The important implications of these data for future disease-association studies are discussed.     

Comparison between mitochondrial and chloroplast DNA variation in the native range of Silene vulgaris

A detailed survey of mitochondrial and chloroplast diversity in eight populations of Silene vulgaris from Central Europe was conducted for comparison with previously published data on diversity from S. vulgaris populations in the introduced range. Mitochondrial DNA (mtDNA) variation around the coxI gene was assessed with Southern blotting/restriction fragment length polymorphism methods. Chloroplast variation was assessed by sequencing the intergenic spacer separating the trnH and psbA genes. Thirty mtDNA haplotypes and 24 chloroplast DNA (cpDNA) haplotypes were found within 86 individuals. The overall genetic diversity h (0.941 for mitochondrial, and 0.893 for chloroplast markers) and within-population diversity were higher than reported in previous population studies of S. vulgaris in the USA and Europe. The frequency of private alleles was surprisingly high - more than 90% for both kinds of markers. Most of our populations were large and located in relatively undisturbed meadows, whereas surveys in Virginia consisted of smaller roadside populations. The slow rate of population turnover in European populations is discussed as a factor responsible for the relatively high diversity of S. vulgaris in undisturbed areas of its native range. Association between mtDNA and cpDNA haplotypes was also demonstrated. Finally, gender and mtDNA haplotype were associated in the Alps populations, where females were very rare.     

mtDNA and the origin of the Icelanders: deciphering signals of recent population history

Previous attempts to investigate the origin of the Icelanders have provided estimates of ancestry ranging from a 98% British Isles contribution to an 86% Scandinavian contribution. We generated mitochondrial sequence data for 401 Icelandic individuals and compared these data with >2,500 other European sequences from published sources, to determine the probable origins of women who contributed to Iceland’s settlement. Although the mean number of base-pair differences is high in the Icelandic sequences and they are widely distributed in the overall European mtDNA phylogeny, we find a smaller number of distinct mitochondrial lineages, compared with most other European populations. The frequencies of a number of mtDNA lineages in the Icelanders deviate noticeably from those in neighboring populations, suggesting that founder effects and genetic drift may have had a considerable influence on the Icelandic gene pool. This is in accordance with available demographic evidence about Icelandic population history. A comparison with published mtDNA lineages from European populations indicates that, whereas most founding females probably originated from Scandinavia and the British Isles, lesser contributions from other populations may also have taken place. We present a highly resolved phylogenetic network for the Icelandic data, identifying a number of previously unreported mtDNA lineage clusters and providing a detailed depiction of the evolutionary relationships between European mtDNA clusters. Our findings indicate that European populations contain a large number of closely related mitochondrial lineages, many of which have not yet been sampled in the current comparative data set. Consequently, substantial increases in sample sizes that use mtDNA data will be needed to obtain valid estimates of the diverse ancestral mixtures that ultimately gave rise to contemporary populations.     

The western and eastern roots of the Saami--the story of genetic "outliers" told by mitochondrial DNA and Y chromosomes

The Saami are regarded as extreme genetic outliers among European populations. In this study, a high-resolution phylogenetic analysis of Saami genetic heritage was undertaken in a comprehensive context, through use of maternally inherited mitochondrial DNA (mtDNA) and paternally inherited Y-chromosomal variation. DNA variants present in the Saami were compared with those found in Europe and Siberia, through use of both new and previously published data from 445 Saami and 17,096 western Eurasian and Siberian mtDNA samples, as well as 127 Saami and 2,840 western Eurasian and Siberian Y-chromosome samples. It was shown that the “Saami motif” variant of mtDNA haplogroup U5b is present in a large area outside Scandinavia. A detailed phylogeographic analysis of one of the predominant Saami mtDNA haplogroups, U5b1b, which also includes the lineages of the “Saami motif,” was undertaken in 31 populations. The results indicate that the origin of U5b1b, as for the other predominant Saami haplogroup, V, is most likely in western, rather than eastern, Europe. Furthermore, an additional haplogroup (H1) spread among the Saami was virtually absent in 781 Samoyed and Ob-Ugric Siberians but was present in western and central European populations. The Y-chromosomal variety in the Saami is also consistent with their European ancestry. It suggests that the large genetic separation of the Saami from other Europeans is best explained by assuming that the Saami are descendants of a narrow, distinctive subset of Europeans. In particular, no evidence of a significant directional gene flow from extant aboriginal Siberian populations into the haploid gene pools of the Saami was found.     

Mitochondrial DNA studies show asymmetrical Amerindian admixture in Afro-Colombian and Mestizo populations

The origin of the African populations that arrived on the Colombian coasts at the time of the Spanish conquest and their subsequent settlement throughout the country and interaction with Amerindian and Spanish populations are features that can be analyzed through the study of mitochondrial DNA (mtDNA) markers. For this purpose, the present study investigates the admixture between these populations by analyzing the markers defining the main (A, B, C, D) and minor (X) founder haplogroups in Native Americans, the principal African haplogroup (L), and additional generic markers present in Caucasian (I, J, K, H, T, U, V, W) and minor African lineages (L3). As part of an interdisciplinary research program (the Expedición Humana, furthered by the Universidad Javeriana and directed by J.E. Bernal V.), 159 Afro-Colombians from five populations in which they are the majority and 91 urban Mestizos were studied. No Amerindian haplogroups (A-D, X) were detected in 81% of the Afro-Colombians. In those samples with Amerindian lineages (average 18.8%, with a range from 10% to 43%), haplogroup B predominated. When analyzed for the presence of African haplotypes, Afro-Colombians showed an overall frequency of 35.8% for haplogroup L mtDNAs, although with broad differences between populations. A few Afro-Colombian samples (1.9%) had mutations that have not been described before, and might therefore be considered as previously unsampled African variants or as new mutations arising in the American continent. Conversely, in Mestizos less than 22% of their mtDNAs belonged to non-Amerindian lineages, of which most were likely to be West Eurasian in origin. Haplogroup L mtDNAs were found in only one Mestizo (1.1%), indicating that, if present, admixture with African women would bring in other, rarer African lineages. On the other hand, in an accompanying paper (Keyeux et al. 2002) we have shown that Amerindians from Colombia have experienced little or no matrilineal admixture with Caucasians or Africans. Taken together, these results are evidence of different patterns of past ethnic admixture among Africans, Amerindians, and Spaniards in the geographic region now encompassing Colombia, which is also reflected in much of the region's cultural diversity.     

Mitochondrial DNA D‐loop sequences suggest a Southeast Asian and Indian origin of Zimbabwean village chickens

This study sought to assess mitochondrial DNA (mtDNA) diversity and phylogeographic structure of chickens from five agro‐ecological zones of Zimbabwe. Furthermore, chickens from Zimbabwe were compared with populations from other geographical regions (Malawi, Sudan and Germany) and other management systems (broiler and layer purebred lines). Finally, haplotypes of these animals were aligned to chicken sequences, taken from GenBank, that reflected populations of presumed centres of domestication. A 455‐bp fragment of the mtDNA D‐loop region was sequenced in 283 chickens of 14 populations. Thirty‐two variable sites that defined 34 haplotypes were observed. In Zimbabwean chickens, diversity within ecotypes accounted for 96.8% of the variation, indicating little differentiation between ecotypes. The 34 haplotypes clustered into three clades that corresponded to (i) Zimbabwean and Malawian chickens, (ii) broiler and layer purebred lines and Northwest European chickens, and (iii) a mixture of chickens from Zimbabwe, Sudan, Northwest Europe and the purebred lines. Diversity among clades explained more than 80% of the total variation. Results indicated the existence of two distinct maternal lineages evenly distributed among the five Zimbabwean chicken ecotypes. For one of these lineages, chickens from Zimbabwe and Malawi shared major haplotypes with chicken populations that have a Southeast Asian background. The second maternal lineage, probably from the Indian subcontinent, was common to the five Zimbabwean chicken ecotypes, Sudanese and Northwest European chickens as well as purebred broiler and layer chicken lines. A third maternal lineage excluded Zimbabwean and other African chickens and clustered with haplotypes presumably originating from South China.     

Genome-wide distribution of linkage disequilibrium in the population of Palau and its implications for gene flow in Remote Oceania

Linkage disequilibrium (LD) between alleles on the same human chromosome results from various evolutionary processes and is thus telling about the history of populations. Recently, LD has garnered substantial interest for its value to map and fine-map disease genes. We examine the distribution of LD between short tandem repeat alleles on autosomes and sex chromosomes in the Remote Oceanic population of Palau to evaluate whether the data are consistent with a recent hypothesis about the origins of genetic variation in Palau, specifically that the population experienced extensive male-biased gene flow following initial settlement. Consistent with evolutionary theory based on effective population size, LD between X-linked alleles is stochastically greater than LD between autosomal alleles, however, small but detectable LD occurs for autosomal markers separated by substantial distances. By contrast, while Y-linked alleles experience only one-third the effective population size of X-linked alleles, their mean value for pairwise LD is only slightly larger than X-linked alleles. For a small population known to experience at least two extreme bottlenecks, 56 six-locus Y haplotypes exhibit remarkable diversity (0.96), comparable to Y diversity of Europeans, however, autosomal and X-linked markers display significantly less diversity, as measured by heterozygosity (4.1% less). Palauan Y haplotypes also fall into distinct clusters, again unlike that of Europe. We argue these data are consistent with waves of male-biased gene flow.     

THE ORIGIN OF WEST EUROPEAN SUBSPECIES OF HONEYBEES (APIS MELLIFERA): NEW INSIGHTS FROM MICROSATELLITE AND MITOCHONDRIAL DATA

Apis mellifera is composed of three evolutionary branches including mainly African (branch A), western and northern European (branch M), and southeastern European (branch C) populations. The existence of morphological clines extending from the equator to the Polar Circle through Morocco and Spain raised the hypothesis that the branch M originated in Africa. Mitochondrial DNA analysis revealed that branches A and M were characterized by highly diverged lineages implying very remote links between both branches. It also revealed that mtDNA haplotypes from lineages A coexisted with haplotypes M in the Iberian Peninsula and formed a south-north frequency cline, suggesting that this area could be a secondary contact zone between the two branches. By analyzing 11 populations sampled along a France-Spain/Portugal-Morocco-Guinea transect at 8 microsatellite loci and the DraI RFLP of the COI-COII mtDNA marker, we show that Iberian populations do not present any trace of “africanization” and are very similar to French populations when considering microsatellite markers. Therefore, the Iberian Peninsula is not a transition area. The higher haplotype A variability observed in Spanish and Portuguese samples compared to that found in Africa is explained by a higher mutation rate and multiple and recent introductions. Selection appears to be the best explanation to the morphological and allozymic clines and to the diffusion and maintenance of African haplotypes in Spain and Portugal.