Genetics of Natural Populations. XXXV. A Progress Report on Genetic Changes in Populations of Drosophila pseudoobscura in the American Southwest

Evolution ◽  
1964 ◽  
Vol 18 (2) ◽  
pp. 164 ◽  
Author(s):  
Th. Dobzhansky ◽  
W. W. Anderson ◽  
O. Pavlovsky ◽  
B. Spassky ◽  
C. J. Wills
Keyword(s):  
Natural Populations ◽  
Progress Report ◽  
American Southwest ◽  
Drosophila Pseudoobscura ◽  
Genetic Changes

Life History Changes in Eastern Mosquitofish (Gambusia holbrooki) Induced by Thermal Elevation

1991 ◽  
Vol 48 (1) ◽  
pp. 60-66 ◽  
Author(s):  
Gary K. Meffe
Keyword(s):  
South Carolina ◽  
Life History ◽  
Nuclear Reactor ◽  
Natural Populations ◽  
Life History Evolution ◽  
Gambusia Holbrooki ◽  
Genetic Changes ◽  
Thermal Death ◽  
Reproductive Biomass ◽  
Eastern Mosquitofish

Much light can be shed on life history evolution through study of responses of organisms to chronic exposure to a novel or perturbed environment. To determine the influence of 28 yr of temporally unpredictable thermal elevation on their life history patterns, I sampled eastern mosquitofish (Gambusia holbrooki) from a thermally elevated (outflow from a nuclear reactor) and an ambient (farm pond) habitat in South Carolina every month for 2 yr. Fish from the artificially heated environment reproduced all year, had higher reproductive investments (higher clutch sizes and reproductive biomass), and smaller offspring than did fish from the ambient environment, which ceased reproduction from October through March, typical for natural populations of the region. Likely environmental factors responsible for these differences include unpredictable food resources, higher mortality from thermal death, and higher predation by fishes and birds in the heated waters. The extent to which these life history alterations are the result of adaptive genetic changes versus phenotypically plastic responses remains to be tested.

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 Micro-geographic variation of inversions in natural populations of Drosophila pseudoobscura

Genetika ◽  
2006 ◽  
Vol 38 (2) ◽  
pp. 97-105 ◽  
Author(s):  
Víctor Salceda ◽  
José Espinoza-Velazquez
Keyword(s):  
Geographic Variation ◽  
Population Sample ◽  
Polytene Chromosomes ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
Drosophila Pseudoobscura ◽  
Natural Habitats ◽  
San Luis ◽  
San Luis Potosi ◽  
San Luis Potosí

Chromosomal polymorphism for the third chromosome in Drosophila pseudoobscura has been widely studied for genetic variation in different environments or locations far apart. However, there is less information regarding sites geographically near one another. Targeting on possible micro-geographic variation in the species, a serial study was done on 12 Mexican populations grouped in four regions, including locations in Durango (DU), the border area of Guanajuato-San Luis Potosi states (GP), Chiapas (CH) and Saldilo (SA). Flies were trapped in their natural habitats using fermenting bananas as bait. They were individually cultivated in the laboratory for larvae production. In a given population sample several flies were cultivated together but only one larva per culture provided salivary tissue to observe polytene chromosomes. Gene arrangements or inversions were identified and frequencies were calculated. A total of 767 third chromosomes were studied and 11 different inversions detected. The type and relative frequencies of the arrangements varied among regions. From the 11 inversions observed, 10 were found in Durango, five in Guanajuato-San Luis Potosi and Chiapas, and eight in Saltillo. The inversion frequencies in the Durango locations varied in four cases, but only one in Chiapas, three cases in Guanajuato-San Luis Potosi, and five in Saltillo. It was also observed that there were geographical gradients for inversions within regions as follows: four arrangements in Saltillo and Durango, three in Guanajuato-San Luis Potos? and one in Chiapas. Moreover, all four regions studied showed evidences for micro-geographical variation. Nevertheless, more studies are needed to elucidate the relevance of the inversion frequencies changes in neighboring populations and also any seasonal-annual frequencies observed in the locations studied here.

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