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1.
J Evol Biol ; 27(6): 1136-48, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24819964

RESUMO

We evaluate for the first time the effect of Wolbachia infection, involving two different supergroups, on the structure and dynamics of the hybrid zone between two subspecies of Chorthippus parallelus (Orthoptera) in the Pyrenees. Wolbachia infection showed no effects on female fecundity or a slight increment in females infected by F supergroup, although in the last case it has to be well established. Cytoplasmic incompatibility (CI) is confirmed in crosses carried out in the field between individuals from a natural hybrid population. This CI, registered as the relative reduction in embryo production (sh ), was of sh = 0.355 and sh = 0.286 in unidirectional crosses involving B and F supergroups, respectively. CI also occurred in bidirectional crosses (sh = 0.147) but with a weaker intensity. The transmission rates of the two Wolbachia strains (B and F) were estimated by the optimization of a theoretical model to reach the infection frequencies observed in certain population. To fit this scenario, both supergroups should present transmission rates close to 1. Further, we have simulated the infection dynamics, and hence, the capacity of Wolbachia to structure the population of the host insects and to affect to reproduction and genetic introgression in the hybrid zone. This represents a first example of the influence of Wolbachia in an insect natural hybrid zone.


Assuntos
Gafanhotos/microbiologia , Interações Hospedeiro-Patógeno , Wolbachia/fisiologia , Animais , Feminino , Fertilidade , Hibridização Genética , Masculino
2.
J Cell Biol ; 31(1): 31-42, 1966 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-5971973

RESUMO

Meiotic chromosomes were isolated from male Oncopeltus fasciatus by dissecting the testes under insect Ringer's solution and spreading the living cells on the Langmuir trough. After being dried by the critical point method, preparations were examined under the electron microscope. Chromosomes at all stages of prophase prove to be multistranded. A significant increase in the number of parallel 250 A fibers in the chromosomes occurs between zygotene and diakinesis. Parallel folding, rather than true multistrandedness, is interpreted as the mechanism responsible for this observed increase in multistrandedness. It has not been possible to determine whether the multistrandedness observed at leptotene represents true multistrandedness or is the result of parallel folding. Apparent multistrandedness is lost at metaphase when the 250 A fibers of the chromosomes become coiled more tightly. In preparations isolated by these methods, no structures other than the 250 A chromosome fibers are visible in the chromomeres, which appear as regionally coiled or folded areas of the fibers along the arm of the chromosome.


Assuntos
Divisão Celular , Cromossomos , Animais , Insetos/crescimento & desenvolvimento , Masculino , Microscopia Eletrônica , Testículo/citologia
3.
Curr Opin Genet Dev ; 2(6): 844-9, 1992 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-1477529

RESUMO

Chromosome variants are well established as useful genetic markers and integral components both of the genetic structure of populations, and in speciation. The current explosion of molecular techniques is facilitating the localization of many DNA sequences, while a reassessment of the fitness of chromosome mutants challenges some classical views on polymorphism and polytypy. Recent experiments on hybrid zones and mathematical modelling have greatly clarified the formation and evolution of chromosome races.


Assuntos
Cromossomos , Genética Populacional , Animais , Humanos , Mutação , Recombinação Genética , Sequências Repetitivas de Ácido Nucleico , Especificidade da Espécie
4.
Evolution ; 54(6): 2081-90, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11209784

RESUMO

The Canary Islands have proven to be an interesting archipelago for the phylogeographic study of colonization and diversification with a number of recent studies reporting evolutionary patterns and processes across a diversity of floral and faunal groups. The Canary Islands differ from the Hawaiian and Galapagos Islands by their close proximity to a continental land mass, being 110 km from the northwestern coast of Africa. This close proximity to a continent obviously increases the potential for colonization, and it can be expected that at the level of the genus some groups will be the result of more than one colonization. In this study we investigate the phylogeography of a group of carabid beetles from the genus Calathus on the Canary Islands and Madeira, located 450 km to the north of the Canaries and 650 km from the continent. The Calathus are well represented on these islands with a total of 29 species, and on the continent there are many more. Mitochondrial cytochrome oxidase I and II sequence data has been used to identify the phylogenetic relationships among the island species and a selection of continental species. Specific hypotheses of monophyly for the island fauna are tested with parametric bootstrap analysis. Data suggest that the Canary Islands have been colonized three times and Madeira twice. Four of these colonizations are of continental origin, but it is possible that one Madeiran clade may be monophyletic with a Canarian clade. The Calathus faunas of Tenerife and Madeira are recent in origin, similar to patterns previously reported for La Gomera, El Hierro, and Gran Canaria.


Assuntos
Besouros , Meio Ambiente , Animais , Ilhas Atlânticas , Besouros/genética , DNA Mitocondrial/química , Geografia , Dados de Sequência Molecular , Filogenia , Densidade Demográfica , Portugal
5.
Evolution ; 54(3): 911-23, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10937264

RESUMO

The genus Brachyderes Schönherr (Coleoptera: Curculionidae) is represented by the species B. rugatus Wollaston on the Canary Islands, with one subspecies on each of the islands of Gran Canaria, Tenerife, La Palma, and El Hierro. These four subspecies are associated with the endemic pine tree Pinus canariensis, and their distributions are broadly coincident. Eighty-eight individual Canarian Brachyderes, sampled from across the distributions of each subspecies, have been sequenced for 570 bp of the mitochondrial DNA (mtDNA) cytochrome oxidase II gene (COII). No mitotypes are shared among islands. Both maximum-likelihood and distance-based phylogenetic analyses have shown that: Tenerife is composed of a single monophyletic clade of mitotypes, El Hierro is composed of a single monophyletic clade occurring within a larger clade comprising all the La Palma mitotypes, and the mitotypes of these three islands form a monophyletic group distinct from Gran Canaria. New methods for estimating divergence times without the assumption of rate constancy have been used to reconstruct the direction and approximate timing of colonizations among the islands. Colonization has occurred from older to progressionally younger islands, and these colonizations are estimated to have occurred less than 2.6 million years ago, although the timing of the initial colonization of the archipelago is not discernable. New methods for the estimation of diversification rates that use branching times as the analyzed variable have been applied to each island fauna. Hypothesized effects of different levels of recent volcanism among islands were not apparent. All islands exhibit a gradually decreasing rate of genetic diversification that is marked by periodic sudden changes in rate.


Assuntos
Besouros/genética , DNA Mitocondrial/química , Complexo IV da Cadeia de Transporte de Elétrons/genética , Animais , Ilhas Atlânticas , Besouros/classificação , Variação Genética , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase
6.
Proc Biol Sci ; 267(1458): 2199-205, 2000 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-11413633

RESUMO

The genus Tarphius Erichson (Coleoptera: Colydiidae) is represented by 29 species on the Canary Islands. The majority are rare, single-island endemics intimately associated with the monteverde (laurel forest and fayal-brezal). The Tarphius canariensis complex is by far the most abundant and geographically wide-spread, occurring on Gran Canaria, Tenerife and La Palma. Eighty-seven individuals from the T. canariensis complex were sequenced for 444 bp of the mitochondrial DNA cytochrome oxidase I gene (COI), 597 bp of the COII gene and the intervening tRNA(leu) gene. A neighbour-joining analysis of maximum-likelihood distances put La Palma as a single monophyletic clade of haplotypes occurring within a larger clade comprising all Tenerife haplotypes. Gran Canarian haplotypes were also monophyletic occurring on a separate lineage. Using a combination of the phylogeographic pattern for T. canariensis, geological data, biogeography of the remaining species and estimated divergence times, we proposed a Tenerifean origin in the old Teno massif and independent colonizations from here to north-eastern Tenerife (Anaga), Gran Canaria and La Palma. New methods of estimating diversification rates using branching times were applied to each island fauna. All islands exhibited a gradually decreasing rate of genetic diversification similar to that seen for Brachyderes rugatus (Coleoptera: Curculionidae) from the Canary Islands.


Assuntos
Besouros/genética , DNA Mitocondrial/genética , Animais , Sequência de Bases , Primers do DNA/genética , Variação Genética , Filogenia , Espanha
7.
Proc Biol Sci ; 261(1361): 173-80, 1995 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-7568271

RESUMO

Fifteen species of the darkling beetle genus Pimelia (Tenebrionidae: Coleoptera) have been sequenced for a 365 b.p. portion of the mitochondrial Cytochrome Oxidase I gene. Thirteen of these are endemic species inhibiting the Canarian archipelago in the Atlantic and the other two are continental conspecifics. This data set has been phylogenetically analysed by maximum parsimony and distance approaches and the resulting trees used to deduce sequential interisland colonization. This suggests patterns compatible with the geological dating of the islands, but with increasing uncertainty when older events are considered. A colonization sequence from Fuerteventura to Tenerife followed by Tenerife to Gran Canarian and La Gomera, and from the latter to La Palma and then to El Hierro is proposed for the genus. A relatively recent secondary colonization from Gran Canaria to Gomera is deduced.


Assuntos
Besouros/genética , DNA Mitocondrial/genética , Filogenia , Animais , Sequência de Bases , Besouros/enzimologia , Complexo IV da Cadeia de Transporte de Elétrons/genética , Variação Genética , Modelos Genéticos , Dados de Sequência Molecular , Homologia de Sequência do Ácido Nucleico , Espanha , Especificidade da Espécie
8.
Proc Biol Sci ; 265(1391): 135-40, 1998 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-9474797

RESUMO

We investigated the phylogeography of Hegeter politus, a saprophagous, flightless darkling beetle endemic to the eastern Canary Islands, using a fragment of the mitochondrial COI gene. Distance and parsimony based gene trees of the mitotypes identified revealed a striking association between mitotype clades and sampling locations. The branching order of the clades suggested that the colonization of the islands by Hegeter politus proceeded from the southern part of Fuerteventura in a north-northeast direction to Lanzarote and the smaller islands. Based on this, a colonization scenario compatible with the reported geological ages and volcanisms of the various parts of the islands has been proposed. The high divergence of the beetles collected from the extreme south of Fuerteventura (the Jandía peninsula) from all other samples has led us to propose that they may be from a new species that has not been described previously. The ecological isolation of Jandía from the rest of Fuerteventura by the sand dunes that cover its narrow isthmus in the north, and the existence of many plant and animal endemisms unique to Jandía, lend supportive evidence to our proposal. The similarities between the evolution of island endemics in the Hawaiian and Canary archipelagos have been discussed. We conclude that many endemics in the Canary archipelago, like the Hawaiian Islands, are most likely to have originated from post-colonization differentiation and divergence.


Assuntos
Besouros/genética , DNA Mitocondrial , Animais , Sequência de Bases , Besouros/classificação , Dados de Sequência Molecular , Filogenia
9.
J Evol Biol ; 14(1): 139-147, 2001 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-29280570

RESUMO

The processes of island colonization and speciation are investigated through mtDNA studies on Canary Island beetles. The genus Nesotes (Coleoptera: Tenebrionidae) is represented by 19 endemic species on the Canary Islands, the majority of which are single island endemics. Nesotes conformis is the most widespread, occurring on Gran Canaria, Tenerife, La Palma and El Hierro. Nesotes conformis forms a paraphyletic assemblage, with a split between Gran Canaria and the other three islands. Nesotes conformis of the western Canary Islands cluster with Nesotes altivagans and Nesotes elliptipennis from Tenerife. Fifty-two individuals from this western islands species complex have been sequenced for 675 base pairs of the mtDNA cytochrome oxidase II gene, representing Tenerife, La Palma and El Hierro. A neighbour joining analysis of maximum likelihood distances resulted in three distinct mtDNA lineages for N. conformis, two of which also include mitotypes of N. altivagans and N. elliptipennis. Through application of parametric bootstrap tests, we are able to reject hypotheses of monophyly for both N. conformis and N. altivagans. Nesotes altivagans and N. elliptipennis are poorly separated morphologically and mtDNA sequence data adds support to this being one species with a highly variable morphology. We propose that N. altivagans/N. elliptipennis is recently derived from two ancestral mtDNA lineages within N. conformis from the Teno region of Tenerife. We further propose colonization of the younger islands of La Palma and El Hierro by N. conformis from a mitochondrial lineage within the Teno massif (colonization; diversification; mitochondrial DNA; Canary Islands; Coleoptera).

10.
Trends Ecol Evol ; 28(12): 696-704, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24091207

RESUMO

Here, we examine the evidence for tree refugia in northern Europe during the Late Pleniglacial (LPG) interval of maximum tree-range contraction. Our review highlights the often equivocal nature of genetic data and a tendency to overestimate potential tree distributions due to warm climate-model bias, and also reveals a convergence of macrofossil and pollen evidence. What emerges is the absence of temperate trees north of 45°N and a west-east (W-E) asymmetry in boreal tree distribution, with a treeless Western Europe north of 46°N, while restricted boreal populations persisted in Eastern Europe up to 49°N, and higher latitudes east of the Fennoscandian ice-sheet. These results have implications for current thinking on European genetic diversity patterns, species migration capacity, and conservation strategies.


Assuntos
Fósseis , Camada de Gelo , Árvores , Europa (Continente) , Geografia , Pólen , Árvores/genética
13.
Heredity (Edinb) ; 99(6): 620-31, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17700634

RESUMO

Large-scale evaluations of genetic diversity in domestic livestock populations are necessary so that region-specific conservation measures can be implemented. We performed the first such survey in European sheep by analysing 820 individuals from 29 geographically and phenotypically diverse breeds and a closely related wild species at 23 microsatellite loci. In contrast to most other domestic species, we found evidence of widespread heterozygote deficit within breeds, even after removing loci with potentially high frequency of null alleles. This is most likely due to subdivision among flocks (Wahlund effect) and use of a small number of rams for breeding. Levels of heterozygosity were slightly higher in southern than in northern breeds, consistent with declining diversity with distance from the Near Eastern centre of domestication. Our results highlight the importance of isolation in terms of both geography and management in augmenting genetic differentiation through genetic drift, with isolated northern European breeds showing the greatest divergence and hence being obvious targets for conservation. Finally, using a Bayesian cluster analysis, we uncovered evidence of admixture between breeds, which has important implications for breed management.


Assuntos
Variação Genética , Repetições de Microssatélites , Carneiro Doméstico/genética , Animais , Europa (Continente) , Carneiro Doméstico/classificação , Especificidade da Espécie
14.
J Evol Biol ; 19(1): 108-13, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16405582

RESUMO

Over several decades, the distribution patterns and evolution of alpine disjunct species has become an increasingly discussed subject. Large scale genetic analysis has allowed the resolution of the past range changes and intraspecific evolution of many species, in Europe especially of Mediterranean origin. However, the phylogeographic structures of species with arctic-alpine disjunct distribution patterns are relatively poorly studied. The existing phylogeographic analysis (mostly of alpine plant species) supports disjunct distributions during glacial as well as post-glacial periods for a number of species. However, several questions still remain unresolved and we therefore analysed the Mountain Ringlet Erebia epiphron as a model for such alpine disjunct species. We found strong differentiation into five different lineages supporting five differentiation centres: (i) the eastern Pyrenees, (ii) the mountain ranges between the central Pyrenees and south-western Alps, (iii, iv) two areas along the southern Alps margin and (v) the northern Alps margin. We propose that these patterns evolved due to the humidity requirements of this species, which did not allow survival in the dry glacial steppes, but along the margins of the wetter glaciated high mountain ranges.


Assuntos
Borboletas/fisiologia , Clima , Demografia , Filogenia , Animais , Borboletas/enzimologia , Borboletas/genética , Análise por Conglomerados , Europa (Continente) , Frequência do Gene , Geografia , Umidade , Isoenzimas
15.
Insect Mol Biol ; 15(1): 45-56, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16469067

RESUMO

Analysis of DNA sequences coding for the C-terminus of spider silk proteins from a range of spiders suggests that many silk C-termini share a common origin, and that their physical properties have been highly conserved over several hundred million years. These physical properties are compatible with roles in protein synthesis, silk function and in recruiting accessory proteins. Phylogenetic relationships among different silk genes suggest that any recombination has been insufficient to homogenize the different types of silk gene, which appear to have evolved independently of one another. The types of nucleotide substitutions that have occurred suggest that selection may have operated differently in the various silk lineages. Amino acid sequences of flagelliform silk C-termini differ substantially from the other types of spider silk studied, but they are expected to have very similar physical properties and may perform a similar function.


Assuntos
Evolução Molecular , Seda/genética , Aranhas/genética , Sequência de Aminoácidos , Animais , Sequência Conservada , Dados de Sequência Molecular , Filogenia , Seda/química
16.
Heredity (Edinb) ; 95(1): 84-90, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16077505

RESUMO

The genome of the European hedgehog, Erinaceus concolor and E. europaeus, shows a strong signal of cycles of restriction to glacial refugia and postglacial expansion. Patterns of expansion, however, differ for mitochondrial DNA (mtDNA) and preliminary analysis of nuclear markers. In this study, we determine phylogeographic patterns in the hedgehog using two loci of the major histocompatibility complex (MHC), isolated for the first time in hedgehogs. These genes show long persistence times and high polymorphism in many species because of the actions of balancing selection. Among 84 individuals screened for variation, only two DQA alleles were identified in each species, but 10 DQB alleles were found in E. concolor and six in E. europaeus. A strong effect of demography on patterns of DQB variability is observed, with only weak evidence of balancing selection. While data from mtDNA clearly subdivide both species into monophyletic subgroups, the MHC data delineate only E. concolor into distinct subgroups, supporting the preliminary findings of other nuclear markers. Together with differences in variability, this suggests that the refugia history and/or expansion patterns of E. concolor and E. europaeus differ.


Assuntos
DNA Mitocondrial/genética , Ouriços/classificação , Ouriços/genética , Filogenia , Animais , Europa (Continente) , Genoma , Geografia , Complexo Principal de Histocompatibilidade , Movimento , Dinâmica Populacional , Seleção Genética
17.
Trends Ecol Evol ; 3(7): 158-67, 1988 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21227192

RESUMO

Hybrid zones are currently of interest because they offer experimental material for studies of the characters and processes involved in divergence and speciation. Parapatric subspecies and races may differ for a whole range of genes and characters, from short DNA sequences through enzymes and chromosomes to morphology and behaviour. An understanding of the origins, evolution, dynamics and fates of these hybrid zone patchworks requires information from a multitude of lines of enwuiry, including taxonomy, genetics, molecular biology, ethology, ecology, biogeography and palaeoclimatology.

18.
Chromosoma ; 56(4): 381-91, 1976 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-949923

RESUMO

Using a modified technique which allowed observation of chromosome orientation in the primary oocyte of grasshoppers at the onset of anaphase, it has been possible to establish that the B-chromosomes is distributed preferentially on the egg side of the metaphase plate rather than the polar body side. The frequency of this preferential orientation matches very closely the level of preferential transmission determined from breeding experiments using individuals from the same population. The spindle is asymmetrical in the primary oocyte of this species, and a possible explanation of the meiotic drive is proposed as a result of the conical shape of nucleoplasm surrounding this spindle. The autosomal chiasma frequency of these females is generally lower than comparable males and is increased by the presence of B chromosomes; but the ciasma frequencies of the sexes respond differently to the addition of 1 and 2 B-chromosomes.


Assuntos
Aberrações Cromossômicas , Cromossomos/ultraestrutura , Gafanhotos/ultraestrutura , Meiose , Oócitos/ultraestrutura , Óvulo/ultraestrutura , Animais , Troca Genética , Feminino , Cariotipagem , Masculino , Fatores Sexuais
19.
Philos Trans R Soc Lond B Biol Sci ; 359(1442): 183-95; discussion 195, 2004 Feb 29.
Artigo em Inglês | MEDLINE | ID: mdl-15101575

RESUMO

An appreciation of the scale and frequency of climatic oscillations in the past few million years is modifying our views on how evolution proceeds. Such major events caused extinction and repeated changes in the ranges of those taxa that survived. Their spatial effects depend on latitude and topography, with extensive extinction and recolonization in higher latitudes and altitudinal shifts and complex refugia nearer the tropics. The associated population dynamics varied with life history and geography, and the present genetic constitution of the populations and species carry attenuated signals of these past dynamics. Phylogeographic studies with DNA have burgeoned recently and studies are reviewed from the arctic, temperate and tropical regions, seeking commonalities of cause in the resulting genetic patterns. Arctic species show distinct shallow genetic clades with common geographical boundaries. Thus Beringia is distinct phylogeographically, but its role as a refugial source is complex. Arctic taxa do not show the common genetic pattern of southern richness and northern purity in north-temperate species. Temperate refugial regions in Europe and North America show relatively deep DNA divergence for many taxa, indicating their presence over several Ice Ages, and suggesting a mode of speciation by repeated allopatry. DNA evidence indicates temperate species in Europe had different patterns of postglacial colonization across the same area and different ones in previous oscillations, whereas the northwest region of North America was colonized from the north, east and south. Tropical montane regions contain deeply diverged lineages, often in a relatively small geographical area, suggesting their survival there from the Pliocene. Our poor understanding of refugial biodiversity would benefit from further combined fossil and genetic studies.


Assuntos
Biodiversidade , Evolução Biológica , Clima , DNA/genética , Meio Ambiente , Animais , Demografia , Geografia , Plantas/genética , Dinâmica Populacional
20.
Heredity (Edinb) ; 34(1): 117-23, 1975 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-1054672

RESUMO

It is proposed that Moraba virgo, the only all-female grasshopper, originated by hybridisation between two extant species P169 and P196. Such an origin accounts for M. virgo's peculiar karyotype and pattern of late replication. The model is predictive and experiments are suggested to test it.


Assuntos
Evolução Biológica , Gafanhotos , Partenogênese , Animais , Cromossomos , Replicação do DNA , Feminino , Hibridização Genética , Cariotipagem , Modelos Biológicos , Probabilidade
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