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

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.

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

Canadian Journal of Genetics and Cytology ◽

10.1139/g85-033 ◽

1985 ◽

Vol 27 (2) ◽

pp. 224-232 ◽

Cited By ~ 31

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.

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POPULATION GENETICS OF ALLOZYME VARIATION IN NEUROSPORA INTERMEDIA

Genetics ◽

10.1093/genetics/80.4.785 ◽

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.

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Parasite variation and the evolution of virulence in a Daphnia-microparasite system

Parasitology ◽

10.1017/s0031182007003939 ◽

2007 ◽

Vol 135 (3) ◽

pp. 303-308 ◽

Cited By ~ 23

Author(s):

T. J. LITTLE ◽

W. CHADWICK ◽

K. WATT

Keyword(s):

Genetic Variation ◽

Rank Order ◽

Genetic Relationships ◽

Natural Populations ◽

Host Genotype ◽

Relative Growth ◽

Trade Off ◽

Relative Growth Rates ◽

Pasteuria Ramosa ◽

Evolution Of Virulence

SUMMARYUnderstanding genetic relationships amongst the life-history traits of parasites is crucial for testing hypotheses on the evolution of virulence. This study therefore examined variation between parasite isolates (the bacterium Pasteuria ramosa) from the crustacean Daphnia magna. From a single wild-caught infected host we obtained 2 P. ramosa isolates that differed substantially in the mortality they caused. Surprisingly, the isolate causing higher early mortality was, on average, less successful at establishing infections and had a slower growth rate within hosts. The observation that within-host replication rate was negatively correlated with mortality could violate a central assumption of the trade-off hypothesis for the evolution of virulence, but we discuss a number of caveats which caution against premature rejection of the trade-off hypothesis. We sought to test if the characteristics of these parasite isolates were constant across host genotypes in a second experiment that included 2 Daphnia host clones. The relative growth rates of the two parasite isolates did indeed depend on the host genotype (although the rank order did not change). We suggest that testing evolutionary hypotheses for virulence may require substantial sampling of both host and parasite genetic variation, and discuss how selection for virulence may change with the epidemiological state of natural populations and how this can promote genetic variation for virulence.

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POPULATION GENETIC CONSEQUENCES OF FEEDING HABITS IN SOME FOREST LEPIDOPTERA

Genetics ◽

10.1093/genetics/92.3.1005 ◽

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.

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Genetic diversity and differentiation in populations of Japanese stone pine (Pinuspumila) in Japan

Canadian Journal of Forest Research ◽

10.1139/x26-162 ◽

1996 ◽

Vol 26 (8) ◽

pp. 1454-1462 ◽

Cited By ~ 31

Author(s):

Naoki Tani ◽

Nobuhiro Tomaru ◽

Masayuki Araki ◽

Kihachiro Ohba

Keyword(s):

Genetic Diversity ◽

Genetic Variation ◽

Genetic Differentiation ◽

Phylogenetic Trees ◽

Genetic Relationships ◽

Natural Populations ◽

Group Method ◽

Stone Pine ◽

Arithmetic Means ◽

Pair Group

Japanese stone pine (Pinuspumila Regel) is a dominant species characteristic of alpine zones of high mountains. Eighteen natural populations of P. pumila were studied in an effort to determine the extent and distribution of genetic diversity. The extent of genetic diversity within this species was high (HT = 0.271), and the genetic differentiation among populations was also high (GST = 0.170) compared with those of other conifers. In previous studies of P. pumila in Russia, the genetic variation within the species was also high, but the genetic differentiation among populations was low. We infer that this difference originates from differences in geographic distribution and ecological differences between the two countries. The genetic variation within each population tended, as a whole, to be smaller within marginal southern populations than within northern populations. Genetic relationships among populations reflect the geographic locations, as shown by unweighted pair-group method with arithmetic means and neighbor-joining phylogenetic trees.

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

Canadian Journal of Forest Research ◽

10.1139/x04-127 ◽

2004 ◽

Vol 34 (12) ◽

pp. 2611-2617 ◽

Cited By ~ 12

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.

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Genetic relationships of eight species of Pacific tunas (Teleostei: Scombridae) inferred from allozyme analysis

Marine and Freshwater Research ◽

10.1071/mf9951021 ◽

1995 ◽

Vol 46 (7) ◽

pp. 1021 ◽

Cited By ~ 18

Author(s):

NG Elliott ◽

RD Ward

Keyword(s):

Liver Enzymes ◽

Genetic Relationships ◽

Phylogenetic Analyses ◽

Allozyme Variation ◽

Allozyme Analysis ◽

Average Heterozygosity ◽

Katsuwonus Pelamis ◽

Thunnus Alalunga ◽

Auxis Thazard ◽

Allozyme Loci

A phylogenetic analysis of eight species of Pacific tunas was made after examining allozyme variation at 23 muscle and liver enzymes encoded by 35 loci. The eight species of tuna were: Thunnus alalunga, albacore; T. obesus, bigeye; T. thynnus orientalis, northern bluefin; T. maccoyii, southern bluefin; T. albacares, yellowfin; Auxis thazard, frigate; Euthynnus affiizii kawakawa; Katsuwonus pelamis, skipjack. All species except the northern bluefin were also examined for variation at three eye-specific loci. The average heterozygosity per locus ranged from 0.038 (frigate) to 0.070 (bigeye). Genetic relationships were examined on the basis of the 35 loci screened in all species. Genetic identities among the five Thunnus species were high, averaging 0.864 and ranging from 0.788 to 0.923. Whereas the albacore appeared to be the most divergent of the Thunnus species (mean identity to other Thunnus species of 0.825, range 0.788-0.452), there was little differentiation between yellowfin, southern bluefin and northern bluefin tunas (mean identity 0.905, range 0.892-0.923), and phylogenetic analyses failed to resolve the branch order among the Thunnus species. The non-Thunnus tunas were quite divergent both from one another and from Thunnus species (mean identity 0.358, range 0.280-0.606). Diagnostic allozyme loci were identified, allowing the discrimination of all species.

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

Canadian Journal of Botany ◽

10.1139/b01-016 ◽

2001 ◽

Vol 79 (4) ◽

pp. 457-463 ◽

Cited By ~ 1

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.

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

Archives of Biological Sciences ◽

10.2298/abs1102381i ◽

2011 ◽

Vol 63 (2) ◽

pp. 381-391 ◽

Cited By ~ 3

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.

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Behavioral variation in Drosophila melanogaster: no evidence for common alleles of large- effect at the foraging gene in a population from North Carolina, USA

10.1101/004325 ◽

2014 ◽

Author(s):

Thomas Turner ◽

Christopher C Giauque ◽

Daniel R Schrider ◽

Andrew D Kern

Keyword(s):

North Carolina ◽

Drosophila Melanogaster ◽

Genetic Variation ◽

Foraging Behavior ◽

Additional Data ◽

Balancing Selection ◽

Natural Populations ◽

Specific Population ◽

Foraging Gene ◽

Population Genetic Variation

It has been postulated that natural populations of Drosophila melanogaster are comprised of two behavioral morphs termed "rover" and "sitter", and that this variation is caused mainly by large-effect alleles at a single locus. Contrary to common assertions, however, published support for the existence of common large effect alleles in nature is quite limited. To further investigate, we quantified the foraging behavior of 36 sequenced strains from a natural population, performed an association study, and described patterns of molecular evolution at the foraging locus. Though there was significant variation in foraging behavior among genotypes, this variation was continuously distributed and not significantly associated with genetic variation at the foraging gene. Patterns of molecular population genetic variation at this gene also provide no support for the hypothesis that for is a target of recent balancing selection. Though our data only apply to this specific population, we propose that additional data is required to support a hypothesis of common alleles of large effect on foraging behavior in nature.

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