scholarly journals GENETICS OF NATURAL POPULATIONS. XIV. A RESPONSE OF CERTAIN GENE ARRANGEMENTS IN THE THIRD CHROMOSOME OF DROSOPHILA PSEUDOOBSCURA TO NATURAL SELECTION

Genetics ◽  
1947 ◽  
Vol 32 (2) ◽  
pp. 142-160 ◽  
Author(s):  
Theodosius Dobzhansky
Keyword(s):  
Natural Selection ◽  
Natural Populations ◽  
Drosophila Pseudoobscura ◽  
The Third

scholarly journals Inversion polymorphism in some natural populations of Drosophila pseudoobscura from central Mexico

Genetika ◽  
2007 ◽  
Vol 39 (3) ◽  
pp. 343-354 ◽  
Author(s):  
Víctor Salceda ◽  
Judith Guzmán ◽  
Olga Olvera
Keyword(s):  
Relative Frequency ◽  
Polytene Chromosomes ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
Drosophila Pseudoobscura ◽  
Central Mexico ◽  
The Third ◽  
Grand Total ◽  
Different Populations ◽  
Single Larva

Samples of D. pseudoobscura were taken in seventeen localities in Central Mexico inside the parallels 18o - 20o N, with the purpose of determine the chromosomal polymorphism in the third of the different populations of this species. From each captured female a single larva of its offspring was taken, its salivary glands extracted and stained with a solution of aceto orcein to observe the polytene chromosomes. From these smears the corresponding karyotype of each larva was determined, keeping a record of them. With the information gathered the relative frequency of each one of the fourteen different inversions found was calculated. A grand total of 1894 third chromosomes were analyzed. The fourteen different inversions found are equivalent to a 34.1 % of the total chromosomal variation of the species. The most abundant inversions found were: TL 50.6 %, CU 27.2 5, SC 9.1 % and EP 5.5 %; the remaining ten inversions detected are in general grounds rare ones with variable relative frequencies depending on the locality. Analysis of the predominant inversions for each population was done. The presence of West-East gradients is reported, even if in cases not so well defined, since as one moves in a particular direction the ups and downs in relative frequency for the alternating pairs TL-CU; TL-SC in the western populations and TL-CU in the eastern ones were observed. The assignment of each population to a particular race was also done, and such a way we were able to recognize three different races coexisting in the area of study.

scholarly journals Natural selection shapes variation in genome-wide recombination rate in Drosophila pseudoobscura

2019 ◽  
Author(s):  
Kieran Samuk ◽  
Brenda Manzano-Winkler ◽  
Kathryn R. Ritz ◽  
Mohamed A.F. Noor
Keyword(s):  
Natural Selection ◽  
Recombination Rate ◽  
Natural Populations ◽  
Amplicon Sequencing ◽  
Drosophila Pseudoobscura ◽  
Global Regulators ◽  
Crossover Rate ◽  
Genome Wide ◽  
Significant Difference ◽  
Long Read

AbstractWhile recombination is widely recognized to be a key modulator of numerous evolutionary phenomena, we have a poor understanding of how recombination rate itself varies and evolves within a species. Here, we performed a comprehensive study of recombination rate (rate of meiotic crossing over) in two natural populations of Drosophila pseudoobscura from Utah and Arizona, USA. We used an amplicon sequencing approach to obtain high-quality genotypes in approximately 8000 individual backcrossed offspring (17 mapping populations with roughly 530 individuals each), for which we then quantified crossovers. Interestingly, variation in recombination rate within and between populations largely manifested as differences in genome-wide recombination rate rather than remodeling of the local recombination landscape. Comparing populations, we discovered individuals from the Utah population displayed on average 8% higher crossover rates than the Arizona population, a statistically significant difference. Using a QST-FST analysis, we found that this difference in crossover rate was dramatically higher than expected under neutrality, indicating that this difference may have been driven by natural selection. Finally, using a combination of short and long read whole-genome sequencing, we found no significant association between crossover rate and structural variation at the 200-400kb scale. Our results demonstrate that (1) there is abundant variation in genome-wide crossover rate in natural populations (2) interpopulation differences in recombination rate may be the result of local adaptation, and (3) the observed variation among individuals in recombination rate is primarily driven by global regulators of crossover rate, with little detected variation in recombination rate among strains across specific tracts of individual chromosomes.

scholarly journals Relative frequencies of the “sex-ratio” inversion in natural populations of Drosophila pseudoobscura from Mexico

Genetika ◽  
2011 ◽  
Vol 43 (2) ◽  
pp. 321-329 ◽  
Author(s):  
Víctor Salceda
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Salivary Glands ◽  
Sex Chromosome ◽  
Natural Populations ◽  
Drosophila Pseudoobscura ◽  
X Chromosomes ◽  
The Third ◽  
Single Larva ◽  
East West

Sex-ratio (proportion of males) in a species is related to a not entirely explained mechanism of sex determination. In Drosophila, sex is determined by the proportion of X chromosomes vs. autosomes. A decrease in the proportion of males vs. females, known as sex-ratio, is characteristic to several Drosophila species, and is related to an inversion in the sexual chromosome the so called ?sex-ratio? (SR) condition. In this occasion we study the presence of that inversion in several populations of Drosophila pseudoobscura from Mexico. With this purpose we did collections of this species on Nevado de Colima,Col., Valpara?so, Zac, Zirahu?n, Mich., Tulancingo, Hgo. and Amecameca, Mex. Flies were captured in nature and carried to the laboratory were individual cultures of each female were established, when the offsprig emerged salivary glands of a single larva from each culture were extracted and stained with an aceto-orcein solution and the corresponding genotype for the third and sex chromosome determined and their relative frequencies calculated. The corresponding frequencies of the ?sex-ratio? inversion in the localities analyzed were: Nevado de Colima 21.8 %, Valparaiso 18.8 %, Zirahu?n 11.4 %, Tulancingo 6.8 % and Amecameca 6.8 %. Apparently an East-West cline distribution is present in these populations. Relative frequencies for inversions in the third chomosome were recorded and relationships between third and X chromosomes inversions performed. Comparisons with similar studies on this and other species are pointed out.

scholarly journals Inversion clines in natural populations of Drosophila pseudoobscura from Mexico

Genetika ◽  
2010 ◽  
Vol 42 (1) ◽  
pp. 67-78
Author(s):  
Víctor Salceda ◽  
Judith Guzmán
Keyword(s):  
Polytene Chromosomes ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
Probable Mechanism ◽  
Drosophila Pseudoobscura ◽  
Isofemale Line ◽  
The Third ◽  
The Usa ◽  
Open Question ◽  
Single Larva

Chromosomal polymorphism in natural populations of Drosophila pseudoobscura have been broadly studied in the USA but scarcely in Mexico where only about 60 localities have been analyzed. Differences among both regions are notorious with respect to their chromosomal constitution. Northern populations, those of USA, have as representative inversions the sequences ST, AR and CH contrasting with those in Southern populations (Mexico) in which prevail the gene arrangements TL, CU and SC. Assuming as a probable mechanism that has allowed these substitutions the flow generated by the presence of a North - South clines, we took as a goal find out if such clines really exist. With that objective in mind we studied 29 populations of this species distributed along four North - South transects. Specimens of D. pseudoobscura caught by attracting them with fermenting bananas were carried to the laboratory where from each female an isofemale line was established. When their offspring appeared a single larva from each isofemale was taken, its salivary glands extracted and stained with a solution of lacto- aceto- orcein, by these means the polytene chromosomes were obtained. On these chromosomes we identified, for each larva, the inversion (s) carried in the third chromosome, in such a way 3439 third chromosomes were analyzed. Among the 29 localities we identified 17 different inversions but the number of them varied from population to population from three to eleven. Relative frequencies of each inversion at every location were calculated and with them for each transect the presence or absence of clines was determined. Among each transect the existence of clines was observed only between two or three near by populations, but we were not able to find a clear manifestation of the presence of clines along a complete transect. Our results at this respect are similar to those previously reported for USA populations. A mechanism that explains North - South substitutions of predominant inversions remains as open question.

scholarly journals Geographical changes in relative frequency of inversions in chromosome III of Drosophila pseudoobscura among natural populations from Mexico

Genetika ◽  
2009 ◽  
Vol 41 (2) ◽  
pp. 155-167
Author(s):  
Víctor Salceda
Keyword(s):  
Polytene Chromosomes ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
Drosophila Pseudoobscura ◽  
Isofemale Line ◽  
The Third ◽  
The Usa ◽  
Chromosome Iii ◽  
Open Question ◽  
Single Larva

Chromosomal polymorphism in natural populations of Drosophila pseudoobscura have been broadly studied in the USA but scarcely in Mexico where only about 60 localities have been analyzed. Differences among both regions are notorious with respect to their chromosomal constitution. Northern populations, those of USA, have as representative inversions the sequences ST, AR and CH contrasting with those in Southern populations (Mexico) in which prevail the gene arrangements TL, CU and SC. Assuming as a probable mechanism that has allowed these substitutions the flow generated by the presence of a North - South clines, we took as a goal find out if such clines really exist. With that objective in mind we studied 29 populations of this species distributed along four North - South transects. Specimens of D. pseudoobscura caught by attracting them with fermenting bananas were carried to the laboratory where from each female an isofemale line was established. When their offspring appeared a single larva from each isofemale was taken, its salivary glands extracted and stained with a solution of lacto-aceto- orcein, by these means the polytene chromosomes were obtained. On these chromosomes we identified, for each larva, the inversion (s) carried in the third chromosome, in such a way 3439 third chromosomes were analyzed. Among the 29 localities we identified 17 different inversions but the number of them varied from population to population from three to eleven. Relative frequencies of each inversion at every location were calculated and with them for each transect the presence or absence of clines was determined. Among each transect the existence of clines was observed only between two or three near by populations, but we were not able to find a clear manifestation of the presence of clines along a complete transect. Our results at this respect are similar to those previously reported for USA populations. A mechanism that explains North - South substitutions of predominant inversions remains as open question.

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