A cline and other patterns of genetic variation in Cochliobolus carbonum isolates pathogenic to corn in North Carolina

1984 ◽  
Vol 62 (5) ◽  
pp. 995-1005 ◽  
Author(s):  
Deborah J. Lodge ◽  
Kurt J. Leonard
Keyword(s):  
North Carolina ◽  
Genetic Variation ◽  
Gene Flow ◽  
Cultural Practices ◽  
Natural Populations ◽  
Cochliobolus Carbonum ◽  
Historical Factors ◽  
Race 2 ◽  
Eastern North Carolina ◽  
High Elevations

Patterns of genetic variation were studied in natural populations of Cochliobolus carbonum Nelson (anamorph Helminthosporium carbonum Ullstrup), a haploid asexually reproducing fungus. Two virulence races (2 and 3) are common on corn in North Carolina. Race 3 has occurred in the Appalachian mountains for at least 25 years, but has recently expanded its range eastward. The expanded range of race 3 cannot be explained by adaptation through parasexual recombination between races or mutation alone. Five polymorphic traits in addition to virulence were compared in races 2 and 3 to evaluate possible recombination between races. If sexual recombination occurred between races, it was rare and was not detected in this study. The simplest explanation for the expansion of race 3 involves historical factors such as increased corn production and changes in weather which aided gene flow. A steep cline was found on the Appalachian escarpment, where the proportion of race 3 isolates dropped from 100% at high elevations to 30% at low elevations over a distance of 7–20 km. No barriers to gene flow were found on the escarpment, suggesting that the environment and possibly cultural practices may restrict race 3 at low elevations and race 2 at high elevations. Race 3 may adapt to conditions in eastern North Carolina only slowly via mutation unless recombination occurs and has gone undetected.

scholarly journals Elucidating the drivers of genetic differentiation in Malaysian torrent frogs (Anura: Ranidae: Amolops): a landscape genomics approach

2019 ◽  
Vol 190 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Kin Onn Chan ◽  
Rafe M Brown
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Genetic Differentiation ◽  
Isolation By Distance ◽  
Variance Partitioning ◽  
Nucleotide Polymorphisms ◽  
Landscape Genomics ◽  
Mountain Ranges ◽  
Historical Factors ◽  
Environmental Attributes

Abstract The interplay between environmental attributes and evolutionary processes can provide valuable insights into how biodiversity is generated, partitioned and distributed. This study investigates the role of spatial, environmental and historical factors that could potentially drive diversification and shape genetic variation in Malaysian torrent frogs. Torrent frogs are ecologically conserved, and we hypothesize that this could impose tight constraints on dispersal routes, gene flow and consequently genetic structure. Moreover, levels of gene flow were shown to vary among populations from separate mountain ranges, indicating that genetic differentiation could be influenced by landscape features. Using genome-wide single nucleotide polymorphisms, in conjunction with landscape variables derived from Geographic Information Systems, we performed distance-based redundancy analyses and variance partitioning to disentangle the effects of isolation-by-distance (IBD), isolation-by-resistance (IBR) and isolation-by-colonization (IBC). Our results demonstrated that IBR contributed minimally to genetic variation. Intraspecific population structure can be largely attributed to IBD, whereas interspecific diversification was primarily driven by IBC. We also detected two distinct population bottlenecks, indicating that speciation events were likely driven by vicariance or founder events.

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

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.

scholarly journals Linking patterns of genetic variation to processes of diversification in Malaysian torrent frogs (Anura: Ranidae:Amolops): a landscape genomics approach

2019 ◽  
Author(s):  
Kin Onn Chan ◽  
Rafe M. Brown
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Isolation By Distance ◽  
Variance Partitioning ◽  
Population Bottlenecks ◽  
Landscape Genomics ◽  
Mountain Ranges ◽  
Historical Factors ◽  
Environmental Attributes ◽  
Isolation By Environment

ABSTRACTThe interplay between environmental attributes and evolutionary processes can provide valuable insights into how biodiversity is generated, partitioned, and distributed. This study investigates the role of spatial, environmental, and historical factors that could potentially drive diversification and shape genetic variation in Malaysian torrent frogs. Torrent frogs are ecologically conserved, and we hypothesize that this could impose tight constraints on dispersal routes, gene flow, and consequently genetic structure. Moreover, levels of gene flow were shown to vary among populations from separate mountain ranges, indicating that genetic differentiation could be influenced by landscape features. Using genome-wide SNPs in conjunction with landscape variables derived from GIS, we performed distance-based redundancy analyses and variance partitioning to disentangle the effects of isolation-by-distance (IBD), isolation-by-environment (IBE), and isolation-by-colonization (IBC). Our results demonstrated that IBE, contributed minimally to genetic variation. Intraspecific population structure can be largely attributed to IBD, whereas interspecific diversification was primarily driven by IBC. We also detected two distinct population bottlenecks, indicating that speciation events were likely driven by vicariance or founder events.

Polymorphisms for lesion type, fungicide tolerance, and mating capacity in Cochliobolus carbonum isolates pathogenic to corn

1978 ◽  
Vol 56 (15) ◽  
pp. 1809-1815 ◽  
Author(s):  
K. J. Leonard
Keyword(s):  
North Carolina ◽  
Coastal Plain ◽  
Toxin Production ◽  
Stabilizing Selection ◽  
Cochliobolus Carbonum ◽  
Linear Lesions ◽  
Lesion Type ◽  
Race 1 ◽  
Fungicide Tolerance ◽  
Race 2

Of 189 isolates of Cochliobolus carbonum from the southeastern and midwestern United States, 3 were race 1, 133 were race 2, and 53 were race 3. The rarity of race 1 which produces a host-specific toxin suggests that, in the absence of host plants sensitive to the toxin, stabilizing selection favors genotypes lacking the gene for toxin production. Race 3 which causes long, linear lesions on corn leaves was predominant among isolates from the Mountains of North Carolina and adjacent states, but was rare in the Piedmont and Coastal Plain where race 2 predominated. Race 2 which causes small round or oval lesions was the only race found in the midwestern United States.Polymorphisms for tolerance of cycloheximide, carboxin, and cadmium were found in race 2 but not in race 3. Only 17% of race 3 isolates had the ability to form perithecia, whereas 67% of race 2 isolates formed perithecia in compatible matings. These differences in polymorphism in addition to the quantitatively inherited difference in lesion type between race 2 and race 3 indicate that there has been little or no gene exchange between races 2 and 3 in nature even though fertile crosses can be obtained readily in the laboratory.

scholarly journals Demographic analyses of a new sample of haploid genomes from a Swedish population of Drosophila melanogaster

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Adamandia Kapopoulou ◽  
Martin Kapun ◽  
Bjorn Pieper ◽  
Pavlos Pavlidis ◽  
Ricardo Wilches ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Gene Flow ◽  
Natural Populations ◽  
Swedish Population ◽  
Demographic Models ◽  
African Populations ◽  
Variation Data ◽  
Adaptive Processes ◽  
Northern Species

AbstractEuropean and African natural populations of Drosophila melanogaster have been the focus of several studies aiming at inferring demographic and adaptive processes based on genetic variation data. However, in these analyses little attention has been given to gene flow between African and European samples. Here we present a dataset consisting of 14 fully sequenced haploid genomes sampled from a natural population from the northern species range (Umeå, Sweden). We co-analyzed this new data with an African population to compare the likelihood of several competing demographic scenarios for European and African populations and show that gene flow improves the fit of demographic models to data.

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.

scholarly journals Female Genotypes Affect Sperm Displacement in Drosophila

Genetics ◽  
1998 ◽  
Vol 149 (3) ◽  
pp. 1487-1493 ◽  
Author(s):  
Andrew G Clark ◽  
David J Begun
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Natural Populations ◽  
Isogenic Line ◽  
Female Fitness ◽  
Sperm Displacement ◽  
Extensive Variation ◽  
Polymorphic Genes ◽  
Displacement Parameter ◽  
Competitive Success

Abstract Differential success of sperm is likely to be an important component of fitness. Extensive variation among male genotypes in competitive success of sperm in multiply mated females has been documented for Drosophila melanogaster. However, virtually all previous studies considered the female to be a passive vessel. Nevertheless, under certain conditions female fitness could be determined by her role in mediating use of sperm from multiple males. Here we ask whether females differ among genotypes in their tendency to exhibit last-male precedence. Competition of sperm from two tester male genotypes (bwD and B3-09, a third-chromosome isogenic line from Beltsville, MD) was quantified by doubly mating female lines that had been rendered homozygous for X, second, or third chromosomes isolated from natural populations. The composite sperm displacement parameter, P2′, was highly heterogeneous among lines, whether or not viability effects were compensated, implying the presence of polymorphic genes affecting access of sperm to eggs. Genetic variation of this type is completely neutral in the absence of pleiotropy or interaction between variation in the two sexes.

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