Microsatellite Loci (microsatellite + locus)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Microsatellite Loci

  • highly polymorphic microsatellite locus
  • new microsatellite locus
  • nuclear microsatellite locus
  • polymorphic microsatellite locus

  • Terms modified by Microsatellite Loci

  • microsatellite locus isolated

  • Selected Abstracts

    Isolation of microsatellite loci in the pollinating fig wasp of Ficus hispida, Ceratosolen solmsi

    INSECT SCIENCE, Issue 4 2008
    Hao Yu
    Abstract Microsatellite loci were isolated for Ceratosolen solmsi, pollinator of the dioecious Ficus hispida. We developed nine polymorphic microsatellite loci based on the method of polymerase chain reaction isolation of microsatellite arrays (PIMA). Enrichment of genomic libraries was performed by random amplified polymorphic DNA (RAPD). A subset of 38 positive clones was sequenced; 15 clones showed microsatellite loci. We tested 15 designed primer pairs and nine of them produced polymorphic amplification in 48 individual wasps collected from different fruits of the dioecious host fig Ficus hispida in China. Among the 48 individuals, 49 alleles were obtained at the nine loci. The observed heterozygosity ranged between 0.357 and 0.634. [source]

    Statistical properties of population differentiation estimators under stepwise mutation in a finite island model

    MOLECULAR ECOLOGY, Issue 4 2002
    F. Balloux
    Abstract Microsatellite loci mutate at an extremely high rate and are generally thought to evolve through a stepwise mutation model. Several differentiation statistics taking into account the particular mutation scheme of the microsatellite have been proposed. The most commonly used is , which is independent of the mutation rate under a generalized stepwise mutation model. and are commonly reported in the literature, but often differ widely. Here we compare their statistical performances using individual-based simulations of a finite island model. The simulations were run under different levels of gene flow, mutation rates, population number and sizes. In addition to the per locus statistical properties, we compare two ways of combining over loci. Our simulations show that even under a strict stepwise mutation model, no statistic is best overall. All estimators suffer to different extents from large bias and variance. While better reflects population differentiation in populations characterized by very low gene-exchange, gives better estimates in cases of high levels of gene flow. The number of loci sampled (12, 24, or 96) has only a minor effect on the relative performance of the estimators under study. For all estimators there is a striking effect of the number of samples, with the differentiation estimates showing very odd distributions for two samples. [source]

    Microsatellite loci from the marine fish Nemadactylus macropterus (Perciformes: Cheilodactylidae)

    MOLECULAR ECOLOGY, Issue 8 2000
    C. P. Burridge

    Microsatellite loci for the fungus Ascosphaera apis: cause of honey bee chalkbrood disease

    Abstract The fungus Ascosphaera apis is a worldwide fungal pathogen of honey bees. To provide tools for understanding the dispersal history of this pathogen, strain differences in virulence, and host,pathogen interactions, we used the draft genome assembly of A. apis to develop microsatellite loci for this species. We present testing results for 25 scorable loci revealing two to eight alleles per locus in a survey of Maryland isolates of this fungus. [source]

    Microsatellite loci for Ponto-Caspian gobies: markers for assessing exotic invasions

    Abstract We developed and tested eight polymorphic microsatellite loci for Ponto-Caspian ,neogobiin' gobies, many of which are invasive in Eurasia and North America, whose study will aid understanding of the population genetics underlying their success. We tested samples from one to two locations from 12 taxa in the recently revised genera Babka, Benthophilus, Mesogobius, Neogobius = Apollonia, Ponticola and Proterorhinus; including the bighead, Caspian, knout, monkey, racer, round, tadpole and tubenose gobies; and taxa from introduced vs. native populations, those diverging between fresh and marine waters, and those differentiated between the Black and Caspian Seas. Populations conformed to Hardy,Weinberg equilibrium expectations, averaging five to 15 alleles per locus and 0.11 to 0.67 mean heterozygosity. Allelic variation significantly differentiated among all taxa and populations. [source]

    Transferability and characterization of nine microsatellite markers for the tropical tree species Tabebuia roseo-alba

    Abstract Microsatellite loci that were previously developed in the tropical tree Tabebuia aurea were used for the genetic analysis of Tabebuia roseo-alba populations. Nine of 10 simple sequence repeat markers were amplified, and the polymorphism was assessed in 58 individuals sampled from two stands in southeastern Brazil. All loci were polymorphic with Mendelian inheritance. The allele numbers were high, ranging from 5 to 13 in population I and 3 to 7 in population II, with means of 8.9 and 5.5, respectively. We conclude that these markers can be efficiently used for parentage and gene-flow studies. [source]

    Microsatellite loci for laticaudine sea kraits

    Abstract We report the development of 11 polymorphic microsatellite loci (three dinucleotides, one trinucleotide and seven tetranucleotides) that are useful for the detection of population subdivision and the study of philopatry, migration and mating biology in laticaudine sea kraits Laticauda saintgironsi and Laticauda laticaudata. Five loci are highly polymorphic and amplify reliably in both L. saintgironsi and L. laticaudata. An additional three are useful in L. saintgironsi and another three in L. laticaudata. [source]

    Microsatellites from kousa dogwood (Cornus kousa)

    Abstract Microsatellite loci were identified from Cornus kousa,National'. Primer pairs for 86 loci were developed and of these, eight were optimized and screened using genomic DNA from 22 kousa cultivars. All optimized loci were polymorphic and the number of alleles per locus ranged from three to 17. Observed heterozygosity ranged from 0 to 0.3 and expected heterozygosity ranged from 0.38 to 0.91. These microsatellites will be useful in population studies, and a breeding programme for cultivar development of Cornus species. [source]

    Microsatellite loci for the plains topminnow (Fundulus sciadicus, Fundulidae)

    Abstract The plains topminnow (Fundulus sciadicus) is a killifish endemic to the Great Plains region. Recent field surveys indicate that populations may be declining in northerly portions of its range and perhaps throughout. Here, we describe the isolation and characterization of 11 microsatellite loci developed for population genetic studies in the species. We also conducted cross-species amplifications to test primer efficacy in five additional taxa, including four killifishes. [source]

    PRIMER NOTE: Isolation and characterization of microsatellite loci in the flat-headed bat (Tylonycteris pachypus)

    P. Y. HUA
    Abstract Microsatellite loci were developed in the flat-headed bat (Tylonycteris pachypus) from genomic DNA using an enriched library method. Nine loci were tested on 48 individuals sampled from Guangxi Province, China. The mean number of observed alleles per locus was 6.4 (range 4,12). Observed and expected heterozygosity values ranged from 0.24 to 0.83 and from 0.30 to 0.89, respectively. One locus revealed significant departure from Hardy,Weinberg equilibrium and no significant linkage disequilibrium was detected between loci pairs. These markers will be used to examine genetic structure and parentage analysis in this species. [source]

    Microsatellite loci in the Propertius duskywing, Erynnis propertius (Lepidoptera: Hesperiidae), and related species

    Abstract Fifteen polymorphic dinucleotide microsatellite loci were characterized for Erynnis propertius using an enrichment protocol. The number of alleles varied from nine to 28 for a sample of 24 individuals. Observed heterozygosities ranged from 0.25 to 0.96. Homozygote excess was detected for 10 loci. Twelve markers successfully amplified in related Erynnis species and eight loci were polymorphic in at least one other species. [source]

    Microsatellite loci for studies on population differentiation and connectivity of the red-bellied yellow tail fusilier, Caesio cuning (Caesionidae)

    Abstract Ten polymorphic microsatellites were isolated from the red-bellied yellow tail fusilier Caesio cuning, a reef-associated fish which occurs widely in the Indo-Pacific region. The species is exploited by both small-scale and commercial fisheries. Fifty individuals from six populations were genotyped using primers that reliably amplified 10 polymorphic loci. The number of alleles per locus ranged from three to 11. Observed heterozygosity (HO) and expected heterozygosity (HE) ranged between 0.400 to 0.880 and 0.337 to 0.843, respectively. These microsatellite loci may be used to study population structure, genetic diversity and connectivity of C. cuning in the range of its distribution. [source]

    Isolation and characterization of polymorphic microsatellites in Parnassius apollo and Euphydryas aurinia (Lepidoptera)

    Abstract Microsatellite loci were developed from Parnassius apollo and Euphydryas aurinia, two endangered Palaearctic butterfly species. Respectively, six and five polymorphic loci were characterized from an enriched partial genomic library. Genetic diversity range from three to 25 alleles for the first species and from seven to 21 for the second. Although the presence of null alleles is suspected, these polymorphic loci are likely to provide important information on the fine scale genetic structure among populations of these species. [source]

    Microsatellite loci for the weaver ant Oecophylla smaragdina

    N. AZUMA
    Abstract We developed 13 microsatellite loci in Oecophylla smaragdina from random amplified polymorphic DNA (RAPD) fragments. These loci showed two to 14 alleles in O. smaragdina with expected heterozygosity of each locus from 0.10 to 0.89, and six were also polymorphic in the related species, O. longinoda. The results suggested that the loci will be useful to analyse the genetic structure of Oecophylla species at both the colony and population levels. [source]

    Microsatellite DNA markers for a grasshopper: Prionotropis hystrix rhodanica (Orthoptera, Pamphagidae)

    R. Streiff
    Abstract Microsatellite loci were isolated from Prionotropis hystrix rhodanica, an endangered grasshopper species, endemic to a steppic area southeast of France. Six polymorphic loci were obtained from an enriched partial genomic libray. A high genetic diversity was observed at all loci, with an observed number of alleles ranging from seven to 29, and an observed heterozygosity between 0.71 and 0.90. Test of cross-amplifications on two closely related taxa are presented. [source]

    Characterization of microsatellite loci for Trigona carbonaria, a stingless bee endemic to Australia

    Catherine L. Green
    Abstract Microsatellite loci were isolated from Trigona carbonaria (family Apidae; tribe Meliponini), a stingless bee endemic to Australia, following the screening of a partial genomic library with several simple-repeat oligonucleotide probes. Polymerase chain reaction (PCR) primers were designed to DNA sequence flanking a selection of trinucleotide and dinucleotide repeat sequences within positive clones. Nine of 10 microsatellite loci were found to be polymorphic amongst 20 unrelated T. carbonaria workers, with observed heterozygosity estimates ranging from 0.168 to 0.800. For many of the primers, distinct polymorphic products were also amplified when used in reactions with DNA from a selection of other bee species. [source]

    Adaptive Units for Conservation: Population Distinction and Historic Extinctions in the Island Scrub-Jay

    Aphelocoma; diversidad genética especie; endémica; genética de conservación; Islas Channel Abstract:,The Island Scrub-Jay (Aphelocoma insularis) is found on Santa Cruz Island, California, and is the only insular bird species in the continental United States. We typed seven microsatellite loci and sequenced a portion of the mitochondrial DNA control region of Island Scrub-Jays and their closest mainland relative, the Western Scrub-Jay (Aphelocoma californica), to assess levels of variability and effective population size and to examine the evolutionary relationship between the two species. The estimated female effective population size, Nef, of the Island Scrub-Jay was 1603 (90% confidence interval: 1481,1738) and was about 7.5% of the size of the mainland species. Island and Western Scrub-Jays have highly divergent control-region sequences, and the value of 3.14 ± 0.09% sequence divergence between the two species suggests a divergence time of approximately 151,000 years ago. Because the four northern Channel Islands were joined as one large island as recently as 11,000 years ago, extinctions must have occurred on the three other northern Channel islands, Santa Rosa, San Miguel, and Anacapa, highlighting the vulnerability of the remaining population. We assessed the evolutionary significance of four island endemics, including the Island Scrub-Jay, based on both genetic and adaptive divergence. Our results show that the Island Scrub-Jay is a distinct species of high conservation value whose history and adaptive potential is not well predicted by study of other island vertebrates. Resumen:, Aphelocoma insularis se encuentra en la Isla Santa Cruz, California, y es la única especie de ave insular en Estados Unidos continental. Clasificamos siete locus microsatelitales y secuenciamos una porción de la región control del ADN mitocondrial de A. insularis y su pariente continental más cercano A. californica para evaluar niveles de variabilidad y tamaño poblacional efectivo y examinar las relaciones evolutivas entre las dos especies. El tamaño poblacional efectivo de hembras, Neh, de A. insularis fue estimado en 1603 (90% CI: 1481-1738) y fue aproximadamente 7.5% del tamaño de la especie continental. Aphelocoma insularis y A. californica tienen secuencias muy divergentes en la región control, y el valor de divergencia secuencial de 3.14 ± 0.09% entre las dos especies sugiere un tiempo de divergencia de aproximadamente 151,000 años. Debido a que las cuatro Islas Channel estuvieron unidas en una sola isla tan recientemente como hace 11,000 años, deben haber ocurrido extinciones en las otras tres islas Channel, Santa Rosa, San Miguel y Anacapa, acentuando la vulnerabilidad de la población remanente. Evaluamos el significado evolutivo de cuatro especies insulares endémicas incluyendo A. insularis con base en la divergencia genética y adaptativa. Nuestros resultados muestran que A. insularis es una especie distinta de alto valor de conservación, cuya historia y potencial adaptativo no es pronosticado correctamente por el estudio de otros vertebrados insulares. [source]

    Amplifying Nuclear and Mitochondrial DNA from African Elephant Ivory: a Tool for Monitoring the Ivory Trade

    cacería furtiva; elefante africano; Loxodonta africana; marfil; microsatélites Abstract: The ability to extract DNA from ivory provides the basis for genetically tracking the origin of poached ivory and thus has important implications for elephant conservation and management. We describe a method to isolate and amplify both genomic and mitochondrial DNA from African elephant ivory that requires very small amounts of ivory taken from any location on the tusk. We pulverized ivory and isolated DNA with a modified QIAamp kit. Ivory as old as 10 to 20 years, stored at ambient conditions, was amenable to DNA isolation with this method. The isolated DNA was robustly amplified at 16 elephant microsatellite loci and two mitochondrial DNA loci. This method has important applications for the forensic analysis of poached African elephant ivory. It enables determination of where stronger antipoaching efforts are needed and provides the basis for monitoring the extent of the trade as well as the consequences of future international trade decisions. Resumen: La habilidad para extraer ADN del marfil proporciona la base para rastrear genéticamente el origen de marfil furtivo y por tanto tiene implicaciones importantes para la conservación y el manejo de elefantes. Describimos un método para aislar y amplificar ADN genómico y mitocondrial de marfil de elefante africano que requiere de cantidades muy pequeñas de marfil tomadas de cualquier parte del colmillo. Pulverizamos el marfil y aislamos el ADN con un equipo QIAamp modificado. Con este método, fue posible aislar el ADN de marfil de 10 a 20 años, conservado en condiciones ambientales. El ADN aislado fue amplificado robustamente en 16 loci microsatélite y dos loci de ADN mitocondrial. Este método tiene aplicaciones importantes para el análisis forense de marfil de elefantes africanos cazados furtivamente. Permite la identificación de sitios donde se requieren mayores esfuerzos para combatir la cacería furtiva y proporciona la base para monitorear la extensión del comercio así como las consecuencias de decisiones futuras de comercio internacional. [source]

    Genetic pattern of the recent recovery of European otters in southern France

    ECOGRAPHY, Issue 2 2008
    Xavier Janssens
    We investigated how landscape affects the population genetic structure and the dispersal of the elusive European otter Lutra lutra in a contemporary colonization context, over several generations and at the level of hydrographic basins. Our study area included 10 basins located in the Cévennes National Park (CNP), at the southern front of the natural otter recovery in France. Each basin comprised 50 to 300 km of permanent rivers that were surveyed for otter presence from 1991 to 2005. Faecal samples collected in 2004 and 2005 in this area were genotyped at 9 microsatellite loci, resulting in the identification of 70 genetically distinct individuals. Bayesian clustering methods were used to infer genetic structure of the populations and to compare recent gene flow to the observed colonization. At the regional level, we identified 2 distinct genetic clusters (NE and SW; FST=0.102) partially separated by ridges, suggesting that the CNP was recolonized by 2 genetically distinct otter populations. At the basin level, the genetic distance between groups of individuals in different basins was positively correlated to the mean slope separating these basins. The probable origins and directions of individual movements (i.e. migration between clusters and basin colonization inside clusters) were inferred from assignment tests. This approach shows that steep and dry lands can stop, impede or divert the dispersal of a mobile carnivore such as the otter. [source]

    Microgeographic genetic isolation in chub (Cyprinidae: Squalius cephalus) population of the Durance River: estimating fragmentation by dams

    C. Dehais
    Dehais C, Eudeline R, Berrebi P, Argillier C. Microgeographic genetic isolation in chub (Cyprinidae: Squalius cephalus) population of the Durance River: estimating fragmentation by dams. Ecology of Freshwater Fish 2010: 19: 267,278. © 2010 John Wiley & Sons A/S Abstract ,, Weirs and dams are wide spread throughout the world's river systems. The most direct effect of these barriers is the limitation of organism movements, i.e., the alteration of connectivity by fragmentation of the aquatic habitat. Whereas the impact of fragmentation on migratory fish species has been well studied, insights on nonmigratory species are still needed. In particular, knowledge on the effects of dams on cyprinid populations at the watershed scale is lacking. Therefore, we studied the genetic structure of eleven chub (Squalius cephalus) samples lined up in the highly fragmented Durance River (France). Using five microsatellite loci, we show that even if the overall genetic differentiation is low, isolation by distance does occur and that genetic diversity increases from upstream to downstream. Dams seem to participate jointly with waterway distance in the explanation of this pattern. However more precise conclusions cannot be made. Guidance for future studies are given. [source]

    Patterns of phenotypic and genetic variability show hidden diversity in Scottish Arctic charr

    C. E. Adams
    Abstract,,, This study examined the degree and pattern of variability in trophic morphology in Arctic charr (Salvelinus alpinus L.) at three spatial scales: across 22 populations from Scotland and between and within two adjacent catchments (Laxford and Shin) in northern Scotland. In addition, the variability at six microsatellite loci between and within the Laxford and Shin systems was determined. Habitat use by charr differed significantly between populations. The pattern of variability in trophic morphology, known to influence foraging ability in charr, showed a very high degree of between-population variation with at least 52% of population pairs showing significant differences in head shape. Trophic morphology and genetic variation was also high over small geographical scales; variation being as high between charr from lakes within the same catchment, as between adjacent catchments. The pattern of both phenotypic and genotypic variation suggests a mosaic of variation across populations with geographically close populations often as distinct from each other as populations with much greater separation. Very low levels of effective migrants between populations, even within the same catchment, suggest that this variation is being maintained by very low straying rates between phenotypically and genetically distinct populations, even when there is no apparent barrier to movement. We conclude that the genetic and phenotypic integrity of charr populations across Scotland is high and that this adaptive radiation constitutes a ,hidden' element of diversity in northern freshwater systems. Two consequences of this are that the population (rather than the species) makes a more rational unit for the consideration of conservation strategies and that the habitat requirements and therefore management needs may differ significantly between populations. [source]

    Do dams increase genetic diversity in brown trout (Salmo trutta)?

    Microgeographic differentiation in a fragmented river
    Abstract , Local genetic differentiation may potentially arise in recently fragmented populations. Brown trout is a polytypic species exhibiting substantial genetic differentiation, which may evolve in few generations. Movement (semi-)barriers in rivers may cause fragmentation, isolation and genetic differentiation in fish. In the Måna River (28 km) flowing from the alpine Lake Møsvatn to the boreal Lake Tinnsjø, construction of four hydropower dams during the period 1906,1957 have fragmented the previously (since last Ice Age) continuous wild resident brown trout population. Samples from the two lakes (N = 40) and six sites in the river (N = 30) isolated at different times were analysed at nine microsatellite loci. All populations showed substantial genetic variation (mean number of alleles per locus 5.3,8.9, observed heterozygosity 0.57,0.65 per population, overall Fst = 0.032). Pairwise multilocus Fst estimates indicated no significant differentiation between populations in the two lakes, and no or little differentiation in the lower river (Fst = 0.0035,0.0091). The microgeographic differentiation among wild resident trout at these sites was less than expected based on similar previous studies. However, results from the upper river, in particular the site immediately below the Lake Møsvatn outlet and dam, indicated isolation (Fst > 0.035). Calculation of genetic distances and assignment tests corroborated these results, as did a significant correlation between years of isolation (since dam construction) and Fst. The population structuring is most likely a result of fragmentation by dams, which has increased overall genetic diversity. This increased local differentiation may be caused by natural selection, but more likely by genetic drift in small, recently fragmented populations. Increased local genetic diversity by genetic drift does not justify conservation measures aiming at preserving genetic diversity. [source]

    High-throughput multiplex microsatellite marker assay for detection and quantification of adulteration in Basmati rice (Oryza sativa)

    ELECTROPHORESIS, Issue 14 2007
    Sunil Archak
    Abstract Basmati rice is a very special type of aromatic rice known world-wide for its extra long grains and pleasant and distinct aroma. Traditional Basmati rice cultivars, confined to Indo-Gangetic regions of the Indian subcontinent, are often reported to be adulterated with crossbred Basmati varieties and long-grain non-Basmati varieties in the export market. At present, there is no commercial scale technology to reliably detect adulteration. We report here a CE-based multiplex microsatellite marker assay for detection as well as quantification of adulteration in Basmati rice samples. The single-tube assay multiplexes eight microsatellite loci to generate variety-specific allele profiles that can detect adulteration from 1% upwards. The protocol also incorporates a quantitative-competitive PCR-based analysis for quantification of adulteration. Accuracy of quantification has been shown to be ±1.5%. The experiments used to develop and validate the methodology are described. [source]

    Distribution patterns of the Q and B biotypes of Bemisia tabaci in the Mediterranean Basin based on microsatellite variation

    B. Simón
    Abstract At least five of the biotypes described in the Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) complex are known to be present in the Mediterranean Basin area. Only two of them, however, are economically relevant, that is, biotypes B and Q. Biological and genetic differences between the two biotypes have been well studied, but less is known about their patterns of genetic variation and population structure. To address these issues, a study was undertaken based on variation at six microsatellite loci among a subset of nine B. tabaci populations (five belonging to the Q and four to the B biotype). The data obtained show that (i) these loci showed considerable polymorphism in the Q and B biotypes populations although the presence of null alleles can obscure the picture; (ii) the Iberian-Q, Canarian-Q, and Egyptian-B populations exhibit heterozygosity excess as a result of bottleneck events; (iii) the low genetic differentiation between the Israeli, Iberian Peninsula, and Italian populations suggest that these populations share a common gene pool; (iv) the genetic distances between the Canarian-Q population and the geographically close population from Morocco indicates spatial isolation and a limited gene flow; and finally (v) the microsatellite data for the B populations indicate that the whiteflies from Egypt and Israel have a close phylogenetic relationship, but the source of these biotype B invasions into the Mediterranean area remains unknown. [source]

    Mating structure and male production in Vespa analis and Vespa simillima (Hymenoptera: Vespidae)

    Jun-ichi TAKAHASHI
    Abstract We estimated queen mating frequency, genetic relatedness between workers and worker reproduction in the hornets Vespa analis and Vespa simillima using microsatellite DNA genotyping. The 20 V. analis colonies studied each contained a queen inseminated by a single male. Of the 15 V. simillima colonies studied, nine had a queen inseminated by a single male, four had a queen inseminated by two males, and two had a queen inseminated by three males. The estimated effective number of matings was 1.33 ± 0.74 (mean ± SD), with 75,85% of the offspring of the six multiply mated queens sired by single males. The values for genetic relatedness between the workers of V. analis and V. simillima were 0.739 ± 0.004 and 0.698 ± 0.013 (mean ± SD), respectively. We conclude that V. analis and V. simillima colonies are genetically monogynous and monandrous. When high relatedness between the workers occurs within colonies, kin selection theory predicts a potential conflict between queens and workers over male production. To determine whether males were derived from queens or workers, males from V. analis and V. simillima colonies were genotyped at four microsatellite loci and the level of ovary activation in workers was determined. None of the 787 V. analis workers and only 15 of 3520 V. simillima workers had developed ovaries. Furthermore, the genotyping identified no worker-produced males in any colony. The presence of reproductive workers correlated positively with the number of workers within the colony. These results suggest that eusocial colonies with an annual life cycle tend to break down socially when they become large and are close to dying. [source]

    Polymorphic microsatellite loci for the swarm-founding wasp Polybia paulista (Hymenoptera: Vespidae)

    Kazuyuki KUDÔ
    Abstract A polymorphic microsatellite locus was isolated and characterized from Polybia paulista, one of the most common polygynic, swarm-founding social wasps in Brazil. Three other microsatellite loci for which the primer sets were originally developed in independent-founding paper wasps also showed polymorphism in the size of amplification products in P. paulista. [source]


    EVOLUTION, Issue 8 2009
    Nolan C. Kane
    While speciation can be found in the presence of gene flow, it is not clear what impact this gene flow has on genome- and range-wide patterns of differentiation. Here we examine gene flow across the entire range of the common sunflower, H. annuus, its historically allopatric sister species H. argophyllus and a more distantly related, sympatric relative H. petiolaris. Analysis of genotypes at 26 microsatellite loci in 1015 individuals from across the range of the three species showed substantial introgression between geographically proximal populations of H. annuus and H. petiolaris, limited introgression between H. annuus and H. argophyllus, and essentially no gene flow between the allopatric pair, H. argophyllus and H. petiolaris. Analysis of sequence divergence levels among the three species in 1420 orthologs identified from EST databases identified a subset of loci showing extremely low divergence between H. annuus and H. petiolaris and extremely high divergence between the sister species H. annuus and H. argophyllus, consistent with introgression between H. annuus and H. petiolaris at these loci. Thus, at many loci, the allopatric sister species are more genetically divergent than the more distantly related sympatric species, which have exchanged genes across much of the genome while remaining morphologically and ecologically distinct. [source]


    EVOLUTION, Issue 10 2008
    Stacey Lee Thompson
    Asexual reproduction has the potential to promote population structuring through matings between clones as well as through limited dispersal of related progeny. Here we present an application of three-gene identity coefficients that tests whether clonal reproduction promotes inbreeding and spatial relatedness within populations. With this method, the first two genes are sampled to estimate pairwise relatedness or inbreeding, whereas the third gene is sampled from either a clone or a sexually derived individual. If three-gene coefficients are significantly greater for clones than nonclones, then clonality contributes excessively to genetic structure. First, we describe an estimator of three-gene identity and briefly evaluate its properties. We then use this estimator to test the effect of clonality on the genetic structure within populations of yellow-cedar (Callitropsis nootkatensis) using a molecular marker survey. Five microsatellite loci were genotyped for 485 trees sampled from nine populations. Our three-gene analyses show that clonal ramets promote inbreeding and spatial structure in most populations. Among-population correlations between clonal extent and genetic structure generally support these trends, yet with less statistical significance. Clones appear to contribute to genetic structure through the limited dispersal of offspring from replicated ramets of the same clonal genet, whereas this structure is likely maintained by mating among these relatives. [source]


    EVOLUTION, Issue 12 2006
    Cock van Oosterhout
    Abstract Our understanding of the evolution of genes of the major histocompatibility complex (MHC) is rapidly increasing, but there are still enigmatic questions remaining, particularly regarding the maintenance of high levels of MHC polymorphisms in small, isolated populations. Here, we analyze the genetic variation at eight microsatellite loci and sequence variation at exon 2 of the MHC class IIB (DAB) genes in two wild populations of the Trinidadian guppy, Poecilia reticulata. We compare the genetic variation of a small (Ne, 100) and relatively isolated upland population to that of its much larger (Ne, 2400) downstream counterpart. As predicted, microsatellite diversity in the upland population is significantly lower and highly differentiated from the population further downstream. Surprisingly, however, these guppy populations are not differentiated by MHC genetic variation and show very similar levels of allelic richness. Computer simulations indicate that the observed level of genetic variation can be maintained with overdominant selection acting at three DAB loci. The selection coefficients differ dramatically between the upland (s 0.2) and lowland (s, 0.01) populations. Parasitological analysis on wild-caught fish shows that parasite load is significantly higher on upland than on lowland fish, which suggests that large differences in selection intensity may indeed exist between populations. Based on the infection intensity, a substantial proportion of the upland fish would have suffered direct or indirect fitness consequences as a result of their high parasite loads. Selection by parasites plays a particularly important role in the evolution of guppies in the upland habitat, which has resulted in high levels of MHC diversity being maintained in this population despite considerable genetic drift. [source]


    EVOLUTION, Issue 5 2000
    Patrick D. Danley
    Abstract Within the past two million years, more than 450 species of haplochromine cichlids have diverged from a single common ancestor in Lake Malawi. Several factors have been implicated in the diversification of this monophyletic clade, including changes in lake level and low levels of gene flow across limited geographic scales. The objectives of this study were to determine the effect of recent lake-level fluctuations on patterns of allelic diversity in the genus Metriaclima, to describe the patterns of population structure within this genus, and to identify barriers to migration. This was accomplished through an analysis of allele frequencies at four microsatellite loci. Twelve populations spanning four species within Metriaclima were surveyed. The effect of lake-level fluctuations can be seen in the reduced genetic diversity of the most recently colonized sites; however, genetic diversity is not depressed at the species level. Low levels of population structure exist among populations, yet some gene flow persists across long stretches of inhospitable habitat. No general barrier to migration was identified. The results of this study are interpreted with respect to several speciation models. Divergence via population bottlenecks is unlikely due to the large allelic diversity observed within each species. Genetic drift and microallopatric divergence are also rejected because some gene flow does occur between adjacent populations. However, the reduced levels of gene flow between populations does suggest that minor changes in the selective environment could cause the divergence of populations. [source]