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Weinberg Expectations (weinberg + expectation)
Selected AbstractsA hybrid zone provides evidence for incipient ecological speciation in Heliconius butterfliesMOLECULAR ECOLOGY, Issue 21 2008CARLOS F. ARIAS Abstract In Heliconius butterflies, it has been proposed that speciation occurs through a combination of divergence in ecological habitat preferences and mimetic colour patterns. Here we test this hypothesis by investigating a parapatric form of the widespread species Heliconius erato. Mendelian (colour patterns) and molecular genetic data permit us to address hypotheses about introgression and genetic differentiation between different populations. Combined analysis of colour pattern, microsatellite loci and mitochondrial DNA showed that Heliconius erato venus and Heliconius erato chestertonii form a bimodal hybrid zone implying partial reproductive isolation. In a sample of 121 individuals collected in sympatry, 25% were hybrids representing a significant deficit of heterozygotes compared to the Hardy,Weinberg expectation. Seven microsatellite loci, analysed for a subset of these individuals, showed marked differentiation between the parental taxa, and unambiguously identified two genotypic clusters concordant with our phenotypic classification of individuals. Mitochondrial DNA analysis showed H. erato venus as a monophyletic group well differentiated from H. erato chestertonii, implying a lack of historical introgression between the populations. Heliconius erato chestertonii is therefore an incipient species that maintains its integrity despite high levels of hybridization. Moreover, H. erato chestertonii is found at higher altitudes than other races of H. erato and has a distinct colour pattern and mimetic relationship. Hence, there are now two examples of parapatric incipient species related to H. erato, H. himera and H. erato chestertonii, both of which are associated with higher altitudes, more arid habitats and distinct mimetic relationships. This implies that parapatric habitat adaptation is a likely cause of speciation in this group. [source] Microsatellite DNA markers for population-genetic studies of blue mackerel (Scomber australasicus) and cross-specific amplification in S. japonicusMOLECULAR ECOLOGY RESOURCES, Issue 3 2009C. Y. TANG Abstract Blue mackerel (Scomber australasicus) is targeted by large-scale purse-seiners in the western North Pacific, and its stock structure is still contentious. Herein, we described 10 polymorphic microsatellite loci for blue mackerel. The number of alleles among 32 individuals surveyed ranged from five to 27 (average of 16.2 alleles per locus). Departures from Hardy,Weinberg expectation were observed at two loci. Cross-specific amplification in the congener, S. japonicus, was successful, except for one locus, revealed to be diagnostic for these congeners. These microsatellite loci will be useful tools to address queries in population genetic structure, fishery management unit and taxonomic species status in the genus Scomber. [source] Genetic signatures in an invasive parasite of Anguilla anguilla correlate with differential stock managementJOURNAL OF FISH BIOLOGY, Issue 1 2010S. Wielgoss In this article, it is shown that available genetic tools for the omnipresent parasite Anguillicoloides crassus in European eels Anguilla anguilla are sensitive to different immigration rates into local A. anguilla stocks for two separated river systems. Relying on four highly polymorphic microsatellite markers, it was inferred that under natural recruitment, nematode samples meet Hardy,Weinberg expectations for a single panmictic population, while genetic signals show signs for a strong Wahlund effect most likely due to very recent population mixing under frequent restocking of young A. anguilla. This was indicated by a low but significant FST value among within-host populations (infrapopulations) along with high inbreeding indices FIS consistent over all loci. The latter signal is shown to stem from high levels of admixture and the presence of first-generation migrants, and alternative explanations such as marker- and sex-specific biases in the nematode populations could be dismissed. Moreover, the slightly increased degree of relatedness within infrapopulations in the stocked river system cannot explain the excessive inbreeding values found and are most likely a direct consequence of recent influx of already infected fish harbouring parasites with different genetic signatures. Applying a simulation approach using known variables from the nematode's invasion history, only the artificial introduction of a Wahlund effect leads to a close match between simulated and real data, which is a strong argument for using the parasite as a biological tag for detecting and characterizing fish translocation. [source] Spatio-temporal variation in the strength and mode of selection acting on major histocompatibility complex diversity in water vole (Arvicola terrestris) metapopulationsMOLECULAR ECOLOGY, Issue 1 2009MATTHEW K. OLIVER Abstract Patterns of spatio-temporal genetic variation at a class II major histocompatibility complex (MHC) locus and multiple microsatellite loci were analysed within and between three water vole metapopulations in Scotland, UK. Comparisons of MHC and microsatellite spatial genetic differentiation, based on standardised tests between two demographically asynchronous zones within a metapopulation, suggested that spatial MHC variation was affected by balancing selection, directional selection and random genetic drift, but that the relative effects of these microevolutionary forces vary temporally. At the metapopulation level, between-year differentiation for MHC loci was significantly correlated with that of microsatellites, signifying that neutral factors such as migration and drift were primarily responsible for overall temporal genetic change at the metapopulation scale. Between metapopulations, patterns of genetic differentiation implied that, at large spatial scales, MHC variation was primarily affected by directional selection and drift. Levels of MHC heterozygosity in excess of Hardy,Weinberg expectations were consistent with overdominant balancing selection operating on MHC variation within metapopulations. However, this effect was not constant among all samples, indicating temporal variation in the strength of selection relative to other factors. The results highlight the benefit of contrasting variation at MHC with neutral markers to separate the effects of stochastic and deterministic microevolutionary forces, and add to a growing body of evidence showing that the mode and relative strength of selection acting on MHC diversity varies both spatially and temporally. [source] Effects of population succession on demographic and genetic processes: predictions and tests in the daylily Hemerocallis thunbergii (Liliaceae)MOLECULAR ECOLOGY, Issue 13 2007MI YOON CHUNG Abstract Spatial genetic structure within plant populations is influenced by variation in demographic processes through space and time, including a population's successional status. To determine how demographic structure and fine-scale genetic structure (FSGS) change with stages in a population's successional history, we studied Hemerocallis thunbergii (Liliaceae), a nocturnal flowering and hawkmoth-pollinated herbaceous perennial with rapid population turnover dynamics. We examined nine populations assigned to three successive stages of population succession: expansion, maturation, and senescence. We developed stage-specific expectations for within-population demographic and genetic structure, and then for each population quantified the spatial aggregation of individuals and genotypes using spatial autocorrelation methods (nonaccumulative O-ring and kinship statistics, respectively), and at the landscape level measured inbreeding and genetic structure using Wright's F -statistics. Analyses using the O-ring statistic revealed significant aggregation of individuals at short spatial scales in expanding and senescing populations, in particular, which may reflect restricted seed dispersal around maternal individuals combined with relatively low local population densities at these stages. Significant FSGS was found for three of four expanding, no mature, and only one senescing population, a pattern generally consistent with expectations of successional processes. Although allozyme genetic diversity was high within populations (mean %P = 78.9 and HE = 0.281), landscape-level differentiation among sites was also high (FST = 0.166) and all populations exhibited a significant deficit of heterozygotes relative to Hardy,Weinberg expectations (range F = 0.201,0.424, mean FIS = 0.321). Within populations, F was not correlated with the degree of FSGS, thus suggesting inbreeding due primarily to selfing as opposed to mating among close relatives in spatially structured populations. Our results demonstrate considerable variation in the spatial distribution of individuals and patterns and magnitude of FSGS in H. thunbergii populations across the landscape. This variation is generally consistent with succession-stage-specific differences in ecological processes operating within these populations. [source] Isolation and characterization of microsatellite loci in the whale shark (Rhincodon typus)MOLECULAR ECOLOGY RESOURCES, Issue 3 2009DENÍ RAMÍREZ-MACÍAS Abstract In preparation for a study on population structure of the whale shark (Rhincodon typus), nine species-specific polymorphic microsatellite DNA markers were developed. An initial screening of 50 individuals from Holbox Island, Mexico found all nine loci to be polymorphic, with two to 17 alleles observed per locus. Observed and expected heterozygosity per locus ranged from 0.200 to 0.826 and from 0.213 to 0.857, respectively. Neither statistically significant deviations from Hardy,Weinberg expectations nor statistically significant linkage disequilibrium between loci were observed. These microsatellite loci appear suitable for examining population structure, kinship assessment and other applications. [source] Characterization of microsatellite loci for the littorine snail Bembicium vittatumMOLECULAR ECOLOGY RESOURCES, Issue 6 2008W. J. KENNINGTON Abstract We describe the isolation and development of 17 polymorphic microsatellite loci for the intertidal snail Bembicium vittatum (Gastropoda: Littorinidae). The loci were tested in 46 individuals from a single population situated near the centre of the species distribution. No evidence of linkage disequilibrium was detected between any pair of loci. However, two loci showed significant departures from Hardy,Weinberg expectations. The number of alleles per locus ranged from two to 15. [source] Characterization of 18 new microsatellite loci in Atlantic cod (Gadus morhua L.)MOLECULAR ECOLOGY RESOURCES, Issue 6 2008SIGURLAUG SKIRNISDOTTIR Abstract Eighteen new microsatellite loci consisting of 10 di-, 5 tri-, 2 tetra- and 1 heptanucleotide repeats are introduced for the Atlantic cod (Gadus morhua L.). All loci were co-amplified in two polymerase chain reactions (plus two previously published microsatellites) and all products were typed clearly. The number of alleles per locus ranged from six (PGmo130) to 45 (PGmo76) and the observed heterozygosity ranged from 0.356 (PGmo130) to 0.957 (PGmo95). All loci except one followed Hardy,Weinberg expectations. Genetic linkage disequilibrium analysis between all pairs of loci did not yield any significant values. [source] Isolation and characterization of polymorphic microsatellite loci in the raccoon (Procyon lotor)MOLECULAR ECOLOGY RESOURCES, Issue 1 2008C. SIRIPUNKAW Abstract We report the isolation and characterization of 17 polymorphic microsatellite loci in the North American raccoon (Procyon lotor). These loci exhibit high levels of allelic diversity, with between four and 13 alleles per locus, and heterozygosity, with observed values of 0.500,1.000 in a sample of 20 individuals. All genotypes conformed to Hardy,Weinberg expectations and there were no instances of linkage disequilibrium detected. [source] Characterization of microsatellite markers for the endemic sand dune lizard, Sceloporus arenicolusMOLECULAR ECOLOGY RESOURCES, Issue 2 2007L. M. CHAN Abstract Here we characterize and report on the genetic variability of eight microsatellite loci for the endemic sand dune lizard, Sceloporus arenicolus, that amplified consistently for individuals throughout the species' range. The number of alleles per locus was high (mean = 13.25) and observed heterozygosities ranged from 0.354 to 0.808. With the exception of a single locus, the loci did not deviate from Hardy,Weinberg expectations. This set of markers is currently being used to examine population structure and landscape genetics in S. arenicolus, a habitat specialist with a restricted range and patchy distribution. [source] Isolation of polymorphic microsatellite markers from Hymeniacidon sinapium (Porifera: Demospongiae: Halichondrida)MOLECULAR ECOLOGY RESOURCES, Issue 3 2006SAYUMI HOSHINO Abstract Eight dinucleotide microsatellite markers were developed on Hymeniacidon sinapium (Porifera: Demospongiae), common littoral sponge around Japan, to investigate population genetic structure. Two to 10 alleles were identified in an analysis of 24 individuals of H. sinapium, with observed heterozygosity ranging from 0.04 to 0.83. All loci did not deviate from the Hardy,Weinberg expectations; however, significant linkage disequilibrium between Sinp126 and Sinp142 was found. [source] Isolation and characterization of microsatellite loci in Alasmidonta heterodon (Bivalvia: Unionidae)MOLECULAR ECOLOGY RESOURCES, Issue 2 2006KRISTINE M. SHAW Abstract We developed 13 species-specific microsatellite markers for the federally endangered Atlantic slope unionid Alasmidonta heterodon. Four to 18 alleles per locus were observed among 30 individuals. Observed heterozygosity throughout the loci ranged from 26.9 to 86.2% and averaged 63.6%. Estimates of individual pairwise genetic distances indicated that levels of genetic diversity among loci were sufficient to produce unique multilocus genotypes for all animals surveyed. Randomization tests showed that genotypes for this collection were consistent with Hardy,Weinberg expectations, and no significant linkage disequilibrium was observed between loci. These loci therefore appear suitable for population surveys, kinship assessment and other such applications. [source] Isolation of polymorphic microsatellite loci in Crossosoma californicum (Crossosomataceae)MOLECULAR ECOLOGY RESOURCES, Issue 2 2005LISA E. WALLACE Abstract Crossosoma californicum (Crossosomataceae) is a rare shrub species endemic to the California Channel Islands. Previous studies based on allozymes revealed little genetic variability in this plant species. We have isolated 13 polymorphic microsatellite loci from C. californicum. These loci show intermediate levels of variability, averaging 4.2 alleles per locus and expected heterozygosity of 0.376. Two loci did not fit Hardy,Weinberg expectations with significant deficits of heterozygous genotypes consistent with the presence of null alleles or population subdivision. [source] Isolation and characterization of microsatellite loci in the Alpine leaf beetle, Oreina elongataMOLECULAR ECOLOGY RESOURCES, Issue 2 2005N. MARGRAF Abstract For a study of local adaptations in the Alpine leaf beetle, Oreina elongata, we developed six microsatellite loci and screened them in 305 individuals from 13 populations. All markers were polymorphic with three to 15 alleles per locus. Average observed and expected heterozygosity values were 0.14 and 0.62, respectively. Four markers showed heterozygote deficiency and deviated significantly from Hardy,Weinberg expectations, indicating the presence of null alleles. [source] Polymorphic microsatellite markers for the goosander (Mergus merganser)MOLECULAR ECOLOGY RESOURCES, Issue 1 2005B. GAUTSCHI Abstract To investigate the population genetic structure of the goosander (Mergus merganser) in Europe and to identify populations with a significant conservation value, we isolated nine microsatellite loci, and screened them in the subspecies Mergus merganser merganser and Mergus merganser americanus. All markers were polymorphic with two to 15 alleles per locus. Average observed and expected heterozygosity values were 0.422 and 0.624, respectively, for the European and 0.497 and 0.667, respectively, for the North American subspecies. Only one marker departed significantly from Hardy,Weinberg expectations in both subspecies. This marker was highly variable but homozygous in all females, suggesting a sex-linked inheritance. [source] Isolation and characterization of microsatellite loci in the Bang's leaf-nosed bat Hipposideros turpisMOLECULAR ECOLOGY RESOURCES, Issue 4 2002Lazaro M. Echenique-Diaz Abstract The Bang's leaf-nose bat, Hipposideros turpis, is an endangered cave-dwelling species inhabiting the southwesternmost islands of Japan. We isolated six dinucleotide microsatellite markers from the partial genomic library of the bat, and examined their allelic variation using a sample (N = 33) from the largest colony in Japan. All the loci showed a moderate allelic variation ranging from two to eight alleles, with the observed heterozygosities from 0.33 to 0.73, and conformed to Hardy,Weinberg expectations. The present microsatellite markers will be useful in assessing population genetic structure and gene flow among populations of this species. [source] Isolation and characterization of microsatellite markers from the Hypoptychus dybowskii (Pisces, Gasterosteiformes)MOLECULAR ECOLOGY RESOURCES, Issue 1 2002Hiroyuki Munehara Abstract Hypoptychus dybowskii (Gasterosteiformes) exhibits allopaternal care frequently caused by various types of male reproductive tactics (sneaking, egg desertion and taking over). In order to understand this interesting reproductive system, we isolated microsatellites loci from H. dybowskii. Five microsatellites showed 2,10 alleles and expected heterozygosities ranged from 0.15 to 0.84. These were not significant deviations from Hardy,Weinberg expectations. These results suggest that these novel polymorphic loci should be useful for parentage analysis of H. dybowskii. [source] Genetic diversity within and between European pig breeds using microsatellite markersANIMAL GENETICS, Issue 3 2006M. SanCristobal Summary An important prerequisite for a conservation programme is a comprehensive description of genetic diversity. The aim of this study was to use anonymous genetic markers to assess the between- and the within-population components of genetic diversity for European pig breeds at the scale of the whole continent using microsatellites. Fifty-eight European pig breeds and lines were analysed including local breeds, national varieties of international breeds and commercial lines. A sample of the Chinese Meishan breed was also included. Eleven additional breeds from a previous project were added for some analyses. Approximately 50 individuals per breed were genotyped for a maximum of 50 microsatellite loci. Substantial within-breed variability was observed, with the average expected heterozygosity and observed number of alleles per locus being 0.56 [range 0.43,0.68] and 4.5 respectively. Genotypic frequencies departed from Hardy,Weinberg expectations (P < 0.01) in 15 European populations, with an excess of homozygotes in 12 of them. The European breeds were on average genetically very distinct, with a Wright FST index value of 0.21. The Neighbour-Joining tree drawn from the Reynolds distances among the breeds showed that the national varieties of major breeds and the commercial lines were mostly clustered around their breeds of reference (Duroc, Hampshire, Landrace, Large White and Piétrain). In contrast, local breeds, with the exception of the Iberian breeds, exhibited a star-like topology. The results are discussed in the light of various forces, which may have driven the recent evolution of European pig breeds. This study has consequences for the interpretation of biodiversity results and will be of importance for future conservation programmes. [source] Fine-scale genetic structure overrides macro-scale structure in a marine snail: nonrandom recruitment, demographic events or selection?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2007SÓNIA C. S. ANDRADE The planktotrophic littorinid species Littoraria flava occupies a continuous habitat on rocky shores close to brackish and freshwater sources. Previous studies of this species have shown a moderate genetic structure over a broad geographical scale, with high deviations from Hardy,Weinberg expectations in many allozymic loci. Local-scale subdivision in marine species with a long dispersal phase is unexpected, but occasionally found. Using a horizontal transect at three locations, we examined whether microscale and short-term subdivision also occurred in L. flava populations and, if so, whether this could explain the Hardy,Weinberg deviations. Littoraria flava showed even more structuring on a microgeographical scale (4,300 m) than on a large-scale (> 200 km). The Ewens,Watterson neutrality test showed that 18% of the tests deviated significantly from the neutrality model. A homogeneity test for each locus across samples within transects showed homogeneous and high FIS values in many loci. These results and the apparent genetic patchiness within transects suggest that asynchronous spawning associated with recurrent colonizations in L. flava can explain the local differentiation without a recognizable pattern. In addition, there could be a balance between these factors and diversifying selection acting on different loci at different times and localities. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 23,36. [source] | ||||||||||