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At least 19 recordsLinked to original sources
PubMed1999

Colonization history of atlantic island common chaffinches (Fringilla coelebs) revealed by mitochondrial DNA.

Common chaffinches (Fringilla coelebs) are thought to have colonized the Atlantic island archipelagoes (the Azores, Madeira, and the Canaries) from neighboring continental populations (Iberia and north Africa) within the last million years. However, colonization may have occurred separately from north Africa to the Canaries and from Iberia to the Azores (as would be predicted geographically) or in one wave from Iberia to the Azores and then to Madeira and the Canaries. These alternatives have different implications for the evolution of morphometric and plumage differentiation in island chaffinches. To determine the most likely colonization route, we estimated the phylogenetic relationships among island and continental subspecies of common chaffinch using sequences from four mtDNA genes (cytochrome b, ATPase 6, NADH 5, and the control region). The most strongly supported mtDNA phylogeny places the continental subspecies together as the sister group to a monophyletic clade containing the island subspecies. This is consistent with a single wave of colonization, and suggests that patterns of similarity among Atlantic island common chaffinches, such as blue pigmentation, short wings, and long tarsi, are due to common colonization history rather than to convergent evolution in a common island environment. However, spectral analysis of phylogenetic splits showed that although monophyly of island haplotypes is favored, there is also substantial support for their polyphyletic origin. We attribute the latter to the confounding effect of homoplasy at multistate sites and to the relatively rapid sequence of colonization events which provided insufficient time for the accumulation of strong phylogenetic signal. These problems are likely to be significant impediments in attempts to test hypotheses of phylogenetic histories of recently evolved populations and taxa.

Adenosine Triphosphatases↗
PubMedDate not supplied

Population genetic structure and colonization sequence of Drosophila subobscura in the Canaries and Madeira Atlantic Islands as inferred by autosomal, sex-linked and mtDNA traits.

The genetic structure in Atlantic Islands and continental populations of Drosophila subobscura has been studied using autosomal and sex-linked allozymes and mitochondrial DNA (mtDNA) haplotypes. From the data it is deduced that whereas the Canary islands have long been isolated, the neighboring island of Madeira has been subjected to continuous migration from the mainland. In addition, sex-linked allozymes and mtDNA data show a large divergence between the geologically younger western islands of the Canarian Archipelago and the older central ones, finding strong founder effects in the former. Divergence rates of sex-linked and mitochondrial genes relative to autosomic loci several times higher than expected under neutrality have been explained by differential migration between sexes. The Canarian Archipelago colonization fits in well with a stepping-stone model of a directional east-west migration that parallels the geological origin of these Islands.

Animals↗
PubMed1999

Genetic Relationships between Haploid and Triploid Targionia (Targioniaceae, Hepaticae).

The species complex Targionia hypophylla-Targionia lorbeeriana includes a haploid and a triploid cytotype in Europe and the Atlantic islands. As shown by isozyme analysis, high levels of fixed heterozygosity and duplication of one of the chromosome sets characterize the triploids that are fertile. Hybridization between two haploids, followed by chromosome doubling and meiotic nondisjunction can explain triploidy. Both allopolyploidy and autopolyploidy are invoked for the origin of the triploid. The duplicated chromosome set most likely comes from the existing haploid that could be one of the putative parents. The morphological intergradation between the two cytotypes, their identical ecological requirements and sympatric distribution can be understood in the light of these data. A haploid Texan colony analyzed for comparison can be discarded as the other putative parent, which remains unknown. Moreover, three triploid African and Australasian colonies do not share the same duplicated genome as the triploids from Europe and the Atlantic islands. Electrophoretic data indicate independent origins of the European-Atlantic and African-Australasian polyploids.

Journal Article↗
PubMed1996

Mitochondrial DNA sequence variation and phylogeography of Pimelia darkling beetles on the island of Tenerife (Canary Islands).

Four morphological taxa of the beetle genus Pimelia (Coleoptera, Tenebrionidae) are known to exist on the Atlantic island of Tenerife. We have obtained DNA sequences for 61 individuals from these taxa across the island for a 200 bp long fragment of the mitochondrial COI gene. In addition, a restriction site polymorphism in the nuclear rRNA ITS-1 sequence was identified and screened in a sample of these individuals using the enzyme Kpn2I. The results were analysed using approaches which allow inferences to be made about the population genetic structure and the mitochondrial genealogy of these closely related beetles. The mtDNA haplotype distribution and the estimates of sequence divergence revealed the presence of two ancient mtDNA lineages which coincide with the disjunct volcanic evolution of the island. The ITS-1 polymorphism was found to be diagnostic of these two lineages. However, the morphological and mitochondrial phylogenies were found to be discordant. We argue that this is possibly the result of rapid morphological change, produced by selection in different habitats, which has been recently superimposed on an older mitochondrial DNA divergence.

Animals↗
PubMed1986

St. Helena familial genu valgum.

A kindred on the mid-Atlantic island of St. Helena has severe "knock knees" and variable lesser malalignment at the elbows and wrists. The disorder is the consequence of hypoplasia of the corresponding bony condyles, with subsequent progressive degenerative osteoarthrophy. Inheritance is autosomal dominant and the condition seems to be a private syndrome which has arisen on the island by recent mutation. In view of the geographical localisation of the disorder and the anatomical distribution of the abnormalities, we propose the title "St. Helena Familial Genu Valgum".

Abnormalities, Multiple↗
PubMed1980

Kinship structure and heterozygosity on Tristan da Cunha.

Although there are many factors influencing the genotype proportions in a small population [1], a heterozygote excess, caused by avoidance of incestuous matings, will often be the expected observation. In the population of the small South-Atlantic islands of Tristan da Cunha, such an excess if observed [2], and we have investigated its origin, partitioning the population by sex and by generation. Although for such a small population the test for random pairing of genes [3, 4] is not sufficiently powerful to produce significant results, the pattern of homozygote deficiency is suggestive of avoidance of close matings. We have also investigated the effect of current nuclear family structure and family-size distribution.

Adolescent↗
PubMed1983

Digital dermatoglyphics of the Faroe Islanders.

Finger dermatoglyphics of 446 male and 463 female Faroe Islanders are described. According to birthplace information for their grandparents the individuals sampled are considered to be representative of all regions of the Faroes. Pattern frequencies are given for individual digits and the tables contain mean radial, ulnar, and unilateral maximal ridge counts. Overall frequencies of patterns and mean total ridge counts in both sexes are compared with other populations in northwestern Europe, several of which have had close historical connections with the Faroes. The Faroese have exceptionally high frequencies of arch and ulnar loop patterns, making their mean pattern intensity index values among the lowest in Europe. Low mean total ridge counts are also characteristic of this population. Icelanders show closer dermatoglyphic resemblance to the Faroese than any other European populations. Low mean total ridge counts among Shetland and Orkney Islanders are noteworthy, and it is possible that the resemblance between these North Atlantic island populations is due to common ancestry arising from Viking settlement during the 8th and 9th centuries. The operation of random genetic drift on the gene pool of the Faroe Islanders is another factor to be considered when assessing their biological affinities.

Demography↗
PubMed1976

The Ornithodoros (Alectorobius) capensis group (Acarina: Ixodoidea: Argasidae) of the palearctic and oriental regions. O. (A.) maritimus: identity, marine bird hosts, virus infections, and distribution in western Europe and northwestern Africa.

In 1967, Vermeil and Marguet described Ornithodoros coniceps maritimus from larvae reared from larvae taken from marine birds on Dumet Island (Atlantic Ocean), Basse Bretagne, France. We collected O. (A.) coniceps Canestrini, 1890, from the type locality (Venice, Italy) and determined that the taxons coniceps and maritimus each require full species status. We selected a lectotype and paralectotypes for the taxon maritimus from the original Dumet Island material. The larva of maritimus is redescribed and the nymph, male, and female are described for the first time. Collection data are recorded from Dumet and other islands off France, Aegimures Islands off Tunisia, Puffin Island off northern Wales, and Great Saltee Island off Ireland. This tick infests nesting colonies of the common tern, roseate tern, sandwich tern, herring gull (northern and Mediterranean races), common cormorant, shag, razorbill, common murre, black-legged kittiwake, and probably other marine birds nesting nearby. Adults and nymphs (tentatively identified as maritimus but lacking associated larvae for full confirmation) were taken near nests of the little egret in Lake Tunis, Tunisia. Soldado virus was isolated from Puffin Island tick samples and a Soldado-like virus from Great Saltee Island tick samples. An experimental study of West Nile virus in the Tunisian tick population is reviewed. The birds species associated with maritimus in each collecting locality, and their nesting and resting habits and migration patterns in relation to tick and arbovirus survival and distribution, will be reported in the following paper in this series.

Animals↗
PubMed2000

Identification of the Diadegma species (Hymenoptera: Ichneumonidae, Campopleginae) attacking the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae).

The species of Diadegma that attack Plutella xylostella (Linnaeus) are revised. Following a morphometric study involving principal components and discriminant analyses, seven distinct morphospecies are recognized. One species is described as new: D. novaezealandiae from New Zealand. Diadegma mollipla (Holmgren) is the name for the species from sub-Saharan Africa and some Indian Ocean and South Atlantic islands. Diadegma varuna Gupta syn. nov. and D. niponica Kusigemati syn. nov. are both synonymized with D. fenestrale (Holmgren). Diadegma xylostellae Kusigemati is strongly presumed to be a synonym of D. semiclausum (Hellén). An illustrated identification key is provided and each species is described in a standard way.

Animals↗
PubMed2000

Multiple sclerosis in time and space--geographic clues to cause.

Geographically MS describes three frequency zones. High frequency areas (prevalence 30+ per 100 000) now comprise most of Europe, Israel, Canada, northern US, southeastern Australia, New Zealand, and easternmost Russia. Medium frequency areas include southern US, most of Australia, South Africa, the southern Mediterranean basin, Russia into Siberia, the Ukraine and parts of Latin America. Prevalence rates under 5 per 100 000 are found in the rest of Asia, Africa and northern South America. Migrants from high to lower risk areas retain the MS risk of their birth place only if they are at least age 15 at migration. Those from low to high increase their risk even beyond that of the natives, with susceptibility extending from about age 11 to 45. Thus MS is ordinarily acquired in early adolescence with a lengthy latency before symptom onset. MS occurred in epidemic form in North Atlantic islands: probably in Iceland and the Shetland-Orkneys; clearly in the Faroe Islands. In the Faroes first symptom onset was in 1943, heralding the first of four successive epidemics at 13 year intervals. The disease was presumably introduced by occupying British troops during World War II, with the postwar occurrences representing later transmissions to and from consecutive cohorts of Faroese. What was transmitted is thought to be a specific, widespread, persistent infection called PMSA (the primary multiple sclerosis affection) which only rarely leads years later to clinical MS. Search for PMSA is best attempted on the Faroes where there are regions still free of MS after 50 years.

Disease Outbreaks↗
PubMed2001

mtDna and the islands of the North Atlantic: estimating the proportions of Norse and Gaelic ancestry.

A total of 1,664 new mtDNA control-region sequences were analyzed in order to estimate Gaelic and Scandinavian matrilineal ancestry in the populations of Iceland, Orkney, the Western Isles, and the Isle of Skye and to investigate other aspects of their genetic history. A relative excess of private lineages in the Icelanders is indicative of isolation, whereas the scarcity of private lineages in Scottish island populations may be explained by recent gene flow and population decline. Differences in the frequencies of lineage clusters are observed between the Scandinavian and the Gaelic source mtDNA pools, and, on a continent-wide basis, such differences between populations seem to be associated with geography. A multidimensional scaling analysis of genetic distances, based on mtDNA lineage-cluster frequencies, groups the North Atlantic islanders with the Gaelic and the Scandinavian populations, whereas populations from the central, southern, and Baltic regions of Europe are arranged in clusters in broad agreement with their geographic locations. This pattern is highly significant, according to a Mantel correlation between genetic and geographic distances (r=.716). Admixture analyses indicate that the ancestral contributions of mtDNA lineages from Scandinavia to the populations of Iceland, Orkney, the Western Isles, and the Isle of Skye are 37.5%, 35.5%, 11.5%, and 12.5%, respectively.

Atlantic Islands↗