Seasonal variation and clonal selection in cyclically parthenogenetic rose aphids (Macrosiphum rosae)

1985 ◽  
Vol 27 (2) ◽  
pp. 224-232 ◽  
Author(s):  
L. R. Rhomberg ◽  
S. Joseph ◽  
R. S. Singh
Keyword(s):  
Genetic Variation ◽  
Seasonal Variation ◽  
Clonal Selection ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Polymorphic Loci ◽  
Esterase Loci ◽  
Allozyme Loci ◽  
Macrosiphum Rosae ◽  
Asexual Cycle

Patterns of geographic and seasonal genetic variation were assessed in natural populations of cyclically parthenogenetic rose aphids Macrosiphum rosae (L.). Nine populations were studied for a red–green colour morph and 30 allozyme loci (20 coding for enzymes and 10 for abundant proteins). Genetic variation was found at 5 of 20 enzyme loci (20%); all 10 abundant proteins proved monomorphic. The average heterozygosity was 4.3%. At some polymorphic loci genotypic frequencies showed significant deviations from Hardy–Weinberg proportions. Six local populations from Hamilton, Ontario, were studied for seasonal variation at the colour locus and at two polymorphic esterase loci (Est-2 and Est-4). All three loci showed large changes in genotypic frequencies over the season during the asexual cycle, but only for Est-4 were changes consistent among populations. This locus undergoes a regular seasonal cycle, the directional changes during the asexual phase presumably being balanced by changes during the sexual phase. The frequencies of three-locus genotypes within each locality fluctuated dramatically over the course of a season, reflecting the domination of local infestations by a few particularly successful clones. We speculate that because of such clonal competition followed by extensive migration, much of the selectively neutral variation is purged from aphid populations. The remaining polymorphic loci, which are mostly di- or tri-allelic, are subject to balancing natural selection at the gene or at closely linked loci. The Est-4 in rose aphids is an example of such a selectively maintained polymorphism.Key words: aphids, allozyme variation, seasonal variation, parthenogenesis, clonal selection, population structure.

scholarly journals POPULATION GENETIC CONSEQUENCES OF FEEDING HABITS IN SOME FOREST LEPIDOPTERA

Genetics ◽  
1979 ◽  
Vol 92 (3) ◽  
pp. 1005-1021
Author(s):  
Charles Mitter ◽  
Douglas J Futuyma
Keyword(s):  
Genetic Variation ◽  
Environmental Heterogeneity ◽  
Feeding Habits ◽  
Functional Relation ◽  
Allozyme Variation ◽  
Unexpected Result ◽  
Polymorphic Loci ◽  
Allozyme Loci ◽  
Race Formation ◽  
Relationship Of

ABSTRACT By surveying variation at allozyme loci in several phytophagous lepidopteran species (Geometridae), we have tested two hypotheses about the relationship of genetic variation to environmental heterogeneity: (1) that allozyme polymorphisms may exist because of associations between genotypes and "niches" (different host plants, in this instance), and (2) that the overall genetic variation of a species is correlated with environmental heterogeneity (or breadth of the species' overall ecological niche) .—Genetic differentiation among samples of oligophagous or polyphagous species taken from different host species was observed in one of three species, at only one of seven polymorphic loci. The data thus provide no evidence for pronounced genetic sub-structuring, or "host race" formation in these sexually reproducing species, although host plant-genotype associations in a parthenogenetic moth give evidence of the potential for diversifying selection.—In a comparison of allozyme variation in polyphagous ("generalized") and oligophagous ("specialized") species, heterozygosity appeared to be higher in specialized species, at all polymorphic loci but one. I t is possible that this unexpected result arises from a functional relation between breadth of diet and genetic variation.

scholarly journals ENZYME VARIABILITY IN THE DROSOPHILA WILLISTONI GROUP. III. AMOUNTS OF VARIABILITY IN THE SUPERSPECIES, D. PAULISTORUM

Genetics ◽  
1972 ◽  
Vol 70 (1) ◽  
pp. 87-112
Author(s):  
Rollin C Richmond
Keyword(s):  
Genetic Variation ◽  
Balancing Selection ◽  
Genetic Relationships ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Metabolizing Enzymes ◽  
Group Iii ◽  
Allozyme Loci ◽  
Drosophila Paulistorum ◽  
Average Individual

ABSTRACT The semispecies composing the superspecies, Drosophila paulistorum, have been analyzed for genetic variation at 17 enzyme loci. On the average a population of D. paulistorum is polymorphic for 55–67% of its loci and an average individual is heterozygous at 21% of its loci. The pattern of genetic variability found supports the hypothesis that allozyme variation is maintained in natural populations by some form of balancing selection. Evidence is presented which supports the hypothesis that glucose-metabolizing enzymes are less genetically variable than non-glucose-metabolizing enzymes. The known genetic relationships between the semispecies of D. paulistorum are discussed in the light of the frequencies of alleles at allozyme loci.

scholarly journals POPULATION GENETICS OF ALLOZYME VARIATION IN NEUROSPORA INTERMEDIA

Genetics ◽  
1975 ◽  
Vol 80 (4) ◽  
pp. 785-805
Author(s):  
P T Spieth
Keyword(s):  
Genetic Variation ◽  
Vegetative Reproduction ◽  
Vascular Plant ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Regular Feature ◽  
Local Populations ◽  
Neurospora Intermedia ◽  
Pattern Of Variation ◽  
High Level

ABSTRACT Electrophoretically detectable variation in the fungus Neurospora intermedia has been surveyed among isolates from natural populations in Malaya, Papua, Australia and Florida. The principal result is a pattern of genetic variation within and between populations that is qualitatively no different than the well documented patterns for Drosophila and humans. In particular, there is a high level of genetic variation, the majority of which occurs at the level of local populations. Evidence is presented which argues that N. intermedia has a population structure analogous to that of an annual vascular plant with a high level of vegetative reproduction. Sexual reproduction appears to be a regular feature in the biology of the species. Substantial heterokaryon function seems unlikely in natural populations of N. intermedia. Theoretical considerations concerning the mechanisms underlying the observed pattern of variation most likely should be consistent with haploid selection theory. The implications of this constraint upon the theory are discussed in detail, leading to the presentation of a model based upon the concept of environmental heterogeneity. The essence of the model, which is equally applicable to haploid and diploid situations, is a shifting distribution of multiple adaptive niches among local populations such that a given population has a small net selective pressure in favor of one allele or another, depending upon its particular distribution of niches. Gene flow among neighboring populations with differing net selective pressures is postulated as the principal factor underlying intrapopulational allozyme variation.

Segregation of allozyme loci in megagametophytes of Engelmann spruce and subalpine fir

Genome ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 103-107 ◽  
Author(s):  
Kathleen L. Shea
Keyword(s):  
Natural Populations ◽  
Segregation Ratio ◽  
Colorado Front Range ◽  
Abies Lasiocarpa ◽  
Front Range ◽  
Subalpine Fir ◽  
Polymorphic Loci ◽  
Engelmann Spruce ◽  
Low Levels ◽  
Allozyme Loci

Segregation ratios and linkage of 10 allozyme loci were examined in haploid megagametophytes obtained from natural populations of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in the Colorado Front Range. For data pooled over trees, the 1:1 segregation ratio expected at Mendelian loci was obtained for five polymorphic loci in 32 Engelmann spruce trees and for seven polymorphic loci in 40 subalpine fir trees. The Gdh and Idh loci in spruce were very tightly linked: no recombinants were detected among 60 megagametophytes of trees heterozygous for both loci. In fir only the Aco and Pgm-1 loci were linked, with an estimated recombination rate of 0.317 ± 0.073. The low levels of among-tree heterogeneity and of segregation distortion found in these populations suggest that reliable estimates of both genetic variation and outcrossing rates can be obtained using allozyme data from these wind-pollinated species.Key words: segregation, linkage, allozymes, Engelmann spruce, subalpine fir.

Allozyme variation, differentiation, and inbreeding in populations of Pinus mugo in Bulgaria

2004 ◽  
Vol 34 (12) ◽  
pp. 2611-2617 ◽  
Author(s):  
Gancho T Slavov ◽  
Peter Zhelev
Keyword(s):  
Genetic Variation ◽  
Growth Form ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
Conservation Status ◽  
Allozyme Variation ◽  
Near Neighbor ◽  
Pinus Mugo ◽  
Mean Values ◽  
Allozyme Loci

Genetic variation of 17 populations of Pinus mugo Turra was studied using 10 polymorphic allozyme loci. Polymorphism and gene diversity in these populations were comparable to mean values for gymnosperm species, but slightly lower than in pines with large and continuous ranges. We did not find significant interpopulation differentiation (FST = 0.041) or isolation by distance, suggesting that gene flow might be extensive or that the time elapsed since the species range became fragmented has been too short for genetic differentiation to arise via genetic drift. We detected moderate and statistically significant levels of inbreeding (mean FIS = 0.252) for all loci in all populations. Although there are many possible explanations for this nonequilibrium population structure, we propose that the main reasons for its ubiquity are the peculiar growth form and reproductive biology of P. mugo, which promote excessive near-neighbor pollinations. Populations in Vitosha Mountain and western Stara Planina had the highest levels of inbreeding and the lowest observed heterozygosities. All populations in these mountains are small and isolated, but none of them is under a special regime of protection. Thus, the conservation status of P. mugo populations in Vitosha Mountain and western Stara Planina may deserve reevaluation. Future gene conservation efforts should focus on obtaining information on the genetic variation of adaptive traits in P. mugo.

Allozyme variation and population structure of Carex humilis var. nana (Cyperaceae) in Korea

2001 ◽  
Vol 79 (4) ◽  
pp. 457-463 ◽  
Author(s):  
Man Kyu Huh
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Genetic Variation ◽  
North American ◽  
Population Level ◽  
Allozyme Variation ◽  
Population Divergence ◽  
Geographic Ranges ◽  
The Mean ◽  
Allozyme Loci

Genetic diversity and population structure of 22 Carex humilis var. nana Ohwi (Cyperaceae) populations in Korea were determined using genetic variation at 23 allozyme loci. This is a long-lived herbaceous species with a widespread distribution in eastern Asia. The 12 enzymes revealed 23 putative loci, of which 11 were polymorphic (47.8%). Genetic diversity at the varietal level and at the population level was 0.131 and 0.118, respectively. Total genetic diversity (HT = 0.274) and within population genetic diversity (HS = 0.256) were high, whereas the extent of the population divergence was relatively low (GST = 0.068). An indirect estimate of the number of migrants per generation (Nm = 3.42) indicated that gene flow was high among Korean populations. Wide geographic ranges, perennial herbaceous nature, and the persistence of multiple generations are associated with the high level of genetic variation. A distinct difference between Asian and North American Carex is shown in the proportion of genetic variation (GST) (p < 0.001). The mean GST of Asian Carex was estimated as 0.056; thus, only 5.6% of genetic variability was distributed among populations, whereas the mean GST of North American Carex was estimated as 19.5% (3.5 times higher). It is probable that the geographical distance between population pairs and presence or absence of glacial history may play roles in the substantial difference between both groups.Key words: Carex humilis var. nana, genetic diversity, population structure.

scholarly journals GENE POLYMORPHISM IN NATURAL POPULATIONS OF DROSOPHILA PERSIMILIS

Genetics ◽  
1977 ◽  
Vol 85 (3) ◽  
pp. 513-520
Author(s):  
Satya Prakash
Keyword(s):  
Genetic Variation ◽  
Gene Polymorphism ◽  
Allele Frequency ◽  
Natural Populations ◽  
Glycolytic Pathway ◽  
Polymorphic Loci ◽  
Chromosome Inversions ◽  
Different Populations ◽  
The Mean ◽  
Drosophila Persimilis

ABSTRACT Genetic variation at 43 loci has been studied in six different populations of Drosophila persimilis by electrophoresis of enzymes and proteins. In D. persimilis the mean proportion of polymorphic loci is 0.362, the mean proportion of heterozygous loci per individual is 0.100 and the average number of alleles per locus is 1.651. In all populations, the loci coding for the hydrolytic and other nonspecific enzymes are much more variable than the loci coding for the enzymes of the glycolytic pathway, Kreb's cycle, other specific enzymes and larval proteins. Most loci have similar allele frequency in all populations except the two loci, Amylase and Pt-12, which show a pattern of associations of different alleles with different third chromosome inversions.

scholarly journals A preliminary study of the allozyme variation in the grey hamster, Cricetulus migratorius (Mammalia: Rodentia), from the Asian part of Turkey

2011 ◽  
Vol 63 (2) ◽  
pp. 381-391 ◽  
Author(s):  
Osman İbiş ◽  
Coşkun Tez ◽  
Servet Özcan ◽  
Metin Kiliç ◽  
Murat Telcioğlu
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Gel Electrophoresis ◽  
Allozyme Variation ◽  
Genetic Distances ◽  
Average Value ◽  
Enzyme Systems ◽  
The Mean ◽  
Preliminary Study ◽  
Allozyme Loci

The aim of the present study was to evaluate the degree of genetic variation and divergence by cellulose acetate gel electrophoresis between samples of Cricetulus migratorius, a cricetine rodent distributed in the Asian part (Anatolia) of Turkey. Out of twenty allozyme loci scored for fifteen enzyme systems, eleven loci were detected to be polymorphic in at least one locality of the Turkish C. migratorius. Indices of genetic variability (the percentage of polymorphic loci, mean number of alleles per locus, and mean observed and expected heterozygosities) were found to be P(95%) = 28, A = 1.3, Ho = 0.226 and He = 0.218, respectively. Nei?s unbiased genetic distances ranged from 0.000 to 0.153, with an average value of 0.069. The mean gene flow was calculated to be Nm = 0.7484. This is a preliminary study describing the allozymic variations of C. migratorius from Turkey. As there are no extensive data on the allozymic variations of C. migratorius from other regions, our results could not be compared, in detail with those of other populations of the species C. migratorius.

scholarly journals LINKAGE DISEQUILIBRIUM IN NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. SEASONAL VARIATION

Genetics ◽  
1977 ◽  
Vol 86 (2) ◽  
pp. 447-454
Author(s):  
Charles H Langley ◽  
Kazuko Ito ◽  
Robert A Voelker
Keyword(s):  
Drosophila Melanogaster ◽  
Seasonal Variation ◽  
Linkage Disequilibrium ◽  
Natural Population ◽  
Natural Populations ◽  
The Other ◽  
Allozyme Loci

ABSTRACT Linkage disequilibrium among ten polymorphic allozyme loci and polymorphic inversions on chromosomes 2 and 3 in a natural population of Drosophila melanogaster was examined early and late in the annual season. Similar to previous studies, little linkage disequilibrium was observed among allozymes. The two significant cases that were observed in the first sample behaved in a contradictory way. One declined much more rapidly than expected due simply to recombination; the other declined slowly as expected. There was little change in allozyme or inversion frequencies during the season.

Allozyme variation in three closely related species of Caucasian rock lizards (Lacerta)

1995 ◽  
Vol 16 (4) ◽  
pp. 331-340 ◽  
Author(s):  
Ross D. MacCulloch ◽  
F.D. Danielyan ◽  
Ilya S. Darevsky ◽  
Robert W. Murphy ◽  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variability ◽  
Genetic Distance ◽  
Related Species ◽  
Allozyme Variation ◽  
Direct Count ◽  
Closely Related Species ◽  
Polymorphic Loci ◽  
Allozyme Loci ◽  
Insular Populations

AbstractGenetic diversity at 37 allozyme loci was surveyed from Lacerta valentini (4 populations), L. portschinskii and L. rudis (1 population each). The number of polymorphic loci ranged from 1 (L. valentini) to 11 (L. rudis). Mean heterozygosity (direct count) ranged from 0.003 (L. valentini) to 0.071 (L. rudis). Nei's (1978) genetic distance ranged from 0-0.03 among populations of L. valentini, 0.127-0.163 between L. valentini and L. rudis and 0.366-0.487 between L. portschinskii and the two other taxa. Indices of genetic variability for species having disjunct distributions were lower than in species with contiguous distributions, similar to the case of insular populations, which have lower values than do mainland populations.

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