Variation In Gene Frequencies Research Articles

GENETIC STRUCTURE AND LOCAL ADAPTATION IN NATURAL INSECT POPULATIONS. Edited by Susan Mopper and Sharon Y. Strauss. Chapman and Hall, New York. 1998. Hardback, £65.00. ISBN 0–412–08031–1.

GENETIC STRUCTURE AND LOCAL ADAPTATION IN NATURAL INSECT POPULATIONS. Edited by Susan Mopper and Sharon Y. Strauss. Chapman and Hall, New York. 1998. Hardback, £65.00. ISBN 0–412–08031–1.

Geographical structure of gene diversity in Quercus petraea (Matt.) Liebl. III. Patterns of variation identified by geostatistical analyses

Geostatistics were used for describing and modelling spatial patterns of gene frequencies at eight allozyme loci in 93 populations of sessile oak well distributed over the natural range of the species. Spatial patterns were summarized by the variogram, a measure of gene frequency variance as a function of distance. They were of three kinds: stationary patterns, clines and random distributions of allele frequencies. The main directions of variation of gene frequencies over Europe were estimated using directional geostatistics. They were shown to reflect postglacial migration routes as well as a genetic divergence among populations from different glacial refugia. A method of spatial interpolation, called kriging, was used to draw synthetic maps for allele frequencies and for multilocus patterns of variation using two canonical variables. It appears from this study that geostatistics are useful tools for the description of complex patterns of genetic variation, and therefore also for the management of natural genetic resources in forest trees.

Geographical structure of gene diversity in Quercus petraea (Matt.) Liebl. III. Patterns of variation identified by geostatistical analyses

Geostatistics were used for describing and modelling spatial patterns of gene frequencies at eight allozyme loci in 93 populations of sessile oak well distributed over the natural range of the species. Spatial patterns were summarized by the variogram, a measure of gene frequency variance as a function of distance. They were of three kinds: stationary patterns, clines and random distributions of allele frequencies. The main directions of variation of gene frequencies over Europe were estimated using directional geostatistics. They were shown to reflect postglacial migration routes as well as a genetic divergence among populations from different glacial refugia. A method of spatial interpolation, called kriging, was used to draw synthetic maps for allele frequencies and for multilocus patterns of variation using two canonical variables. It appears from this study that geostatistics are useful tools for the description of complex patterns of genetic variation, and therefore also for the management of natural genetic resources in forest trees.

Breeding structure ofGlossina pallidipes(Diptera: Glossinidae) populations in East and southern Africa

AbstractGene diversity and gene flow inGlossina pallidipesAusten were studied by using allozyme electrophoresis on samples from southern and East Africa. Recorded were 30 alleles segregating at eight loci. Gene diversity was 0.212±0.085 S.E. in four southern African populations and 0.163±0.076 in seven Kenyan populations. All loci were in Hardy-Weinberg equilibrium.Pgmand 6pgdwere sex linked. Spatial components of gene diversity were measured by usingFstatistics. Mating was random within each population. The ‘fixation index’FSTwas 0.133±0.062 among southern African populations. Among the Kenyan populations.FSTwas 0.159±0.069.FSTwas 0.238±0.051 among all populations. Analysis of variance of gene frequencies showed that 65.8% of the genetic variance lay within populations and 34.2% of the genetic variance lay between Kenyan and southern African populations. These data suggest a strong measure of genetic drift among tsetse populations even in a region where it is thought they are continuously distributed. The causes of this drift require investigation.

Geographic variation within populations of Panolis flammea (Lepidoptera: Noctuidae) in Britain

AbstractGel electrophoresis was used to study isoenzyme variation in Panolis flammea Denis Schiffermüller from a total of eight forest sites in England and Scotland dominated by either Scots or lodgepole pine. Four polymorphic loci (esterase, malate dehydrogenase, isocitrate dehydrogenase and 6-phosphogluconate dehydrogenase) were examined in adult moths. Most of the genotype frequencies conformed to Hardy-Weinberg expectations. An estimate of standardized gene frequency variance (Fst=0.109 ±0.032) indicated that there was significant genetic differentitation between populations. There was in addition a latitudinal cline in allele frequency at the 6-phosphogluconate dehydrogenase locus. The possible role of variation between P. flammea populations in contributing to regional differences in pest status is briefly discussed.

Gene Flow between Univoltine and Semivoltine Northern Corn Rootworm (Coleoptera: Chrysomelidae) Populations

Semivoltinism in northern corn rootworm beetles, Diabrotica barberi Smith & Lawrence, is an evolutionary response to a cultural control method in parts of the Corn Belt in the north central United States. Semivoltine beetles are at a marked reproductive disadvantage compared with univoltine beetles in fields where maize, zea mays, is planted annually because their reproductive rates are effectively half those of the univoltine beetles. In fields where corn is rotated with another crop, however, univoltine beetle larvae die. Beetles, therefore, are subject to disruptive selection because both types of corn planting are practiced even on the same farms. Allozyme markers at 12 polymorphic loci were used to study gene flow among beetle populations in rotated and in continuous corn fields at each of three farms in northwestern Iowa. Sampled were both free-flying beetles and beetles eclosing in cages in the fields where they had bred. Variance in gene frequencies among the cage-emerged beetles was partitioned. Of the variance, 48% was attributed to corn fields in farms (rotated versus continuous), and 52% to farms. The Wright fixation index was F ST = 0.0056 ± 0.0023 for cage-emerged beetles among all fields. F statistics were greater in magnitude among cage-emerged, locally bred, beetles than among free-flying beetles. Gene flow between diapause phenotypes was virtually unrestricted, and the rate of spread and adaptation to rotated corn fields is likely to be slow.

Analysis of gene flow in North American face fly (Musca autumnalis) populations

Vertical polyacrylamide gel electrophoresis was used to resolve enzymes at ten putative loci in face flies Musca autumnalis De Geer, a colonizing, Palaearctic species established in North America for at least 210 generations. Flies were sampled in 1991 from six locations in Iowa, two in Maryland, two in Minnesota, two in Tennessee, three in New York, and three in Missouri. Nondirectional temporal variation in gene frequencies over a 4-year interval was detected at farms in central Iowa. Heterogeneity in allele frequencies was detected among farms in Iowa, Maryland, New York and Minnesota but not in Tennessee and Missouri. There were no consistent departures from random mating. Partitioning variances in gene frequencies showed that 58% of the variation occurred in populations among states and 43% between populations within states. Mean reproducing immigrants per population per generation was estimated to be eighteen flies. No regional genetic differentiation was detected, and there were no barriers to gene flow within or among diverse populations in the six states. Earlier data bearing on gene flow among and between Nearctic and Palearctic face fly samples were analysed and significant differentiation was not detected.

Tay-Sachs disease in persons of French-Canadian heritage in northern New England.

This study sought to determine whether persons of French-Canadian heritage in northern New England are at high risk for the lethal infantile form of Tay-Sachs disease. In order to accomplish this, death records and laboratory diagnostic records were surveyed to ascertain Tay-Sachs deaths in a cohort of 372,000 live births between 1977-1986. The proportion of the total population with French-Canadian or Jewish heritage was determined from census and birth records, and the ethnic background of Tay-Sachs cases was determined from the corresponding birth records. In 1,860 births, both parents were of Ashkenazi Jewish heritage. One of those children was diagnosed with Tay-Sachs disease. In 41,000 births, both parents were of French-Canadian heritage, and in an additional 93,000 births, one parent was of French-Canadian heritage. No cases of Tay-Sachs disease were identified in the offspring of those individuals. Approximately 14 cases (95% confidence interval 8-20) would be expected, if the gene frequency approximated that reported for individuals of Ashkenazi Jewish heritage. Based on the results of this study, routine testing for Tay-Sachs disease heterozygosity is not indicated for persons of French-Canadian heritage in northern New England. This conclusion may not necessarily be valid for persons of French-Canadian heritage residing in other states. Further studies of Tay-Sachs disease mutations and prevalence among persons of French-Canadian heritage will be important to determine possible regional variations in gene frequencies.

Phenotypic variation along a cline in allozyme and karyotype frequencies, and its relationship with habitat, in the dog-whelk Nucella lapillus, L.

The dog-whelk Nucella lapillus exhibits a number of phenotypic variations and genetic polymorphisms which correlate with habitat-specific environmental pressures, especially those associated with wave action and temperature. This study investigates the relationship between genetic composition (karyotypic and electrophoretic variation) and phenotypic differentiation in N. lapillus sampled at 15 points along an 8 km stretch of coastline. Coincident clinal variation in gene frequencies and shell shape is described; they covary with differences in karyotype and also with growth. Laboratory-reared young show that differences in phenotype (shell shape and growth) are inherited. Experimental evidence is presented that specific shell shapes are adaptive under conditions of thermal stress. Together with the well-established correlations between shell shape and shore exposure, this association provides an argument for a relationship between genetic composition, phenotype and habitat in this species.

Phenotypic variation along a cline in allozyme and karyotype frequencies, and its relationship with habitat, in the dog-whelk Nucella lapillus, L.

The dog-whelk Nucella lapillus exhibits a number of phenotypic variations and genetic polymorphisms which correlate with habitat-specific environmental pressures, especially those associated with wave action and temperature. This study investigates the relationship between genetic composition (karyotypic and electrophoretic variation) and phenotypic differentiation in N. lapillus sampled at 15 points along an 8 km stretch of coastline. Coincident clinal variation in gene frequencies and shell shape is described; they covary with differences in karyotype and also with growth. Laboratory-reared young show that differences in phenotype (shell shape and growth) are inherited. Experimental evidence is presented that specific shell shapes are adaptive under conditions of thermal stress. Together with the well-established correlations between shell shape and shore exposure, this association provides an argument for a relationship between genetic composition, phenotype and habitat in this species.

Genetic Zoogeography of theMysis relictaSpecies Group (Crustacea: Mysidacea) in Northern Europe and North America

The zoogeography and systematics of the Mysis relicta species group were elucidated in an allozyme survey of populations across northern Europe and North America. The North American populations are here identified as an independent species (sp. IV), distinct from the three previously recognized European M. relicta group taxa (spp. I–III). The geographical pattern of gene frequency variation in North America supports a late-glacial colonization by separate eastern and western refugial stocks of sp. IV. In Europe, sp. III is known from a single subarctic lake, while both spp. I and II are widespread. They coexist in the Baltic Sea, but their lacustrine distributions are largely different. Species I accounts for most Fennoscandian populations and those in Poland and Germany whereas sp. II lives in Ireland, parts of southwestern Scandinavia, and Karelia. With the paleohydrographical reference, the distributions suggest that both species survived the last glaciation in proglacial lakes east of the Scandinavian Ice. Subsequent distributional differentiation was influenced by environmental variations; the dispersal of sp. II in southwestern Scandinavia was facilitated by a broader euryhalinity than that in sp. I and other stenohaline "glacial relief" crustaceans. The Irish populations may represent a distinct refugial stock within sp. II.

Maintenance of genetic variation in hatchery stocks of Atlantic salmon, Salmo salar L.: experiences from the River Bush, Northern Ireland

. An examination of biochemical-genetic variation at seven polymorphic loci was carried out among five year classes of wild Atlantic salmon, Salar L., in the R. Bush and in a hatchery strain derived from the wild population. Within some of the year classes, gene frequencies at several loci differed significantly between wild and artificially reared salmon. Highly significant temporal variation in gene frequencies was detected among successive year classes of the hatchery strain, while this was less significant among the wild salmon. Samples of wild salmon taken as 0+ and 1 + parr in the river showed no significant temporal variability in allelic frequencies. Heterozygosity levels among the wild and hatchery-reared salmon were comparable, averaging 0·185 and 0·176 respectively. The genetic variability of the artificially reared salmon is discussed in relation to numbers of broodstock and breeding regime used at the hatchery.

Variation in Gene Frequencies for Two Loci Among Assamese Tai

Previous articleNext article No AccessReportsVariation in Gene Frequencies for Two Loci Among Assamese TaiM. N. Phookan and T. Shyamacharan SinghM. N. Phookan Search for more articles by this author and T. Shyamacharan Singh Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Current Anthropology Volume 35, Number 2Apr., 1994 Sponsored by the Wenner-Gren Foundation for Anthropological Research Article DOIhttps://doi.org/10.1086/204258 Views: 2Total views on this site Copyright 1994 The Wenner-Gren Foundation for Anthropological ResearchPDF download Crossref reports no articles citing this article.

Gene Diversity in Natural Diabrotica barberi Smith & Lawrence Populations (Coleoptera: Chrysomelidae)

A survey of electrophoretic loci in Diabrotica barberi Smith & Lawrence showed that 21 of 27 loci were polymorphic. Mean gene diversity at the polymorphic loci was 0.274 ± 0.051 and 0.213 ± 0.041 among all 27 loci. Gene frequencies were heterogeneous among collections of adult beetles from 14 farms in five counties in northwestern Iowa. About half the variance in gene frequencies was partitioned among farms in counties and half among the counties. Wright’s F statistics showed that most departures from random mating occurred within populations; departures from random mating among populations were insignificant. The data show much gene flow among D. barberi populations.

Allozyme variation in stable flies (Diptera: Muscidae)

Polyacrylamide gel electrophoresis was used to resolve allozymes in the cosmopolitan blood-feeding stable fly, Stomoxys calcitrans (L.). Nineteen of 38 loci were polymorphic (53%). Mean heterozygosities among all loci and among only polymorphic loci were 0.096 and 0.182, respectively. These gene diversity measures are about half those among other muscid Diptera. Variation in gene frequencies was examined in 10 natural stable fly populations from Iowa and Minnesota. Gene frequencies were homogeneous at five of eight loci among six populations in 1990 and eight of eight loci among four populations in 1992. Wright's F statistics showed no significant departure from random mating among stable flies. It was concluded that gene flow compensates for any local differentiation in stable fly populations.

Population Structure in Heliothis virescens (Lepidoptera: Noctuidae): an Estimate of Gene Flow

Starch gel electrophoresis was used to evaluate the genetic population structure of the tobacco budworm, Heliothis virescens (F.). A total of 1,836 adult male moths were collected from 60 trap sites throughout Texas, Louisiana, Mississippi, Arkansas, and Georgia during a 4-wk period in 1989. An average of 30.6 (±0.4) moths was electrophoretically analyzed per trap. Genotypic proportions showed no significant departures from Hardy-Weinberg expectations, suggesting random mating within populations. Population differentiation, measured by the standardized gene frequency variance, F st, was low ( F st = 0.002 ± 10−4) but highly significant. This indicates an average local population size, Nm , of 135 (±10 using a jackknife estimate), the highest value we can find reported. This figure suggests a combination of high mobility ( m ) and high population size ( N ). Hierarchical F statistics were estimated using three levels: (1) traps within localities, (2) localities (traps within 8 km of each other) within regions, and (3) regions (localities within 80 km of each other). There was significant heterogeneity at all distance scales; however, gene frequency variance between regions and variance between localities within regions was low compared with variance within localities. These F statistics indicate that the extent of a local panmictic population has an average diameter on the order of 8 km or less.

Allozyme variation in European populations of the oyster Ostrea edulis

Variations at 22 enzyme coding loci were surveyed in 11 populations of the oyster Ostrea edulis L., which were sampled between 1988 and 1990 along the Atlantic and Mediterranean coasts of Europe. Atlantic oyster beds suffered a steady decline during the last century, and restocking of beds with oysters of foreign origin has probably resulted in a high degree of interbreeding of natural oyster stocks from all Atlantic Europe. Our study confirms the low levels of genetic variability previously reported for the oyster populations from the Atlantic coasts, and extends it to the Mediterranean coasts. The locus arginine-kinase (ARK *) exhibited a high degree of interpopulation differentiation (F ST=0.289), resulting from extensive variation in gene frequencies along a geographical cline. However, the overall genetic differentiation between populations was slight, and similar to that reported for other local populations of bivalves (mean genetic distance between populations is 0.010, mean F ST=0.062). A general pattern of increasing differentiation along the coastline in an Atlantic-mediterranean direction emerged; but genetic differentiation among the Atlantic populations was not significantly lower than that observed among the Mediterranean populations. This and other results suggest that the effects of extensive transplantation of oysters among various areas in Europe are detectable only in some particular localities. The geographical distribution of low-frequency alleles suggests a restriction to gene flow outwards from the Mediterranean Sea, across the Straits of Gibraltar.

Genetic differentiation between spatially-disjunct populations of the deep-sea, hydrothermal vent-endemic amphipod Ventiella sulfuris

Species endemic to deep-sea hydrothermal vent ecosystems have disjunct distributions imposed by the island-like arrangement of their specialized habitats. Using allozyme electrophoresis, we examined genetic population structure of the hydrothermal vent amphipod Ventiella sulfuris Barnard and Ingram, 1990. Samples from five sites along the East Pacific Rise (EPR) and two along the Galapagos Rift were collected in 1990 and 1988, respectively. Variability, based on 12 enzyme loci, was relatively high $$\bar P$$ (proportion of polymorphic loci whose most common allele not greater than 0.95 in frequency) =41.6%; $$\bar H$$ (mean heterozygosity) =0.158] compared with shallow-water marine and freshwater amphipods, and similar to the deep-sea lysianassid Eurythenes gryllus. Genetic divergence among populations spread along a contiguous rift axis (i.e., EPR) was low [Nei's genetic distance (D) ranged from <0.001 to 0.018]. Genetic tructure analysis suggests that along a contiguous ridge axis migration occurs in a stepping stone manner and is unconstrained by distances as great as 1200 km (migration rate, $$\bar M$$ , ranged from 1.9 to 67.8 ind. generation−1). However, genetic divergence between populations on disjunct ridge axes was extremely high (D ranged from 0.438 to 0.476). Most of the variance in gene frequencies was due to the differences between the major subpopulations inhabiting the two distinct ridge axes, EPR and Galapagos Rift. Apparently, very little migration and gene flow occur between these major subpopulations (M≪1). This level of genetic divergence may be sufficient to justity separation of EPR and Galapagos Rift populations at the species level. Futher analyses of morphological characters is required before taxonomic status can be assigned.

Geographical Variation and Biosystematics of Sand Myrtle, Leiophyllum buxifolium (Ericaceae)

Leiophyllum buxifolium occurs in a series of disjunct population systems in three areas: the New Jersey Pine Barrens, the Coastal Plain of North and South Carolina, and the southeastern Blue Ridge Province. Twelve populations from six regions within this range were examined for divergence in morphology and allozyme frequencies. There is significant variation at the level of region for seven of the 15 morphological characters examined and significant variation at the level of population within region for 12 characters. Allozyme variation in L. buxifolium is lower than in other long-lived, woody species, with HT = 0.118 ? 0.022 (mean ? standard deviation) and Hs = 0.108 ? 0.062. On the other hand, the percentage of loci polymorphic is high (64.6 ? 21.8). More of the total variation in gene frequencies occurs among regions (GRT = 0.075 ? 0.059) than among populations within regions (GPR = 0.036 ? 0.035). Multivariate analyses indicate that the Hanging Rock region in the Piedmont of North Carolina is distinct based on morphology, but not based on isozyme markers. No other region appeared to be distinct from the others either morphologically or genetically. Leiophyllum should, therefore, be treated as a monotypic genus that, despite its high degree of morphological variability within and among disjunct areas, cannot be easily split into well-defined infraspecific taxa.

SPERM-MEDIATED GENE FLOW AND THE GENETIC STRUCTURE OF A POPULATION OF THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI.

The genetic structure of populations of sessile and sedentary organisms is often characterized by microgeographic differentiation in gene frequencies and deviations from panmixia. In many terrestrial botanical systems, restricted gene flow via seed and pollen dispersal may have an important role in promoting such genetic patterns. Until recently, however, limited dispersal of the sexual propagules of benthic invertebrates has not been considered to play a comparable role in aquatic systems. Based on paternity analyses in the field using rare allozyme markers, it appears that concentrations of sibling sperm of the sessile, colonial ascidian Botryllus schlosseri decline rapidly within 50 cm of a source colony. In combination with spatially restricted dispersal of brooded larvae, limited dispersal of sperm should enhance the potential for genetic diversification and inbreeding. However, analysis of allelic and genotypic frequencies at three independent, polymorphic allozyme loci using F-statistics provides little evidence for microgeographic variation in gene frequencies. This lack of differentiation can be explained in terms of the absolute number (rather than concentration) of gametes and larvae dispersing from a point source, which-depending on diffusion and geometric assumptions-may actually increase with distance. In contrast to the absence of differentiation, levels of inbreeding are high, even within the confines of 25 times 25-cm quadrats. The absence of genetic diversification and presence of inbreeding caution against inferring levels and causes of gene flow from indirect analysis of genetic structure and, conversely, making predictions about genetic and breeding structure based solely on direct analysis of gene flow.