Fitness Analysis of the "Sex-Ratio" Polymorphism in Experimental Populations of Drosophila pseudoobscura

1983 ◽  
Vol 121 (5) ◽  
pp. 630-648 ◽  
Author(s):  
Andrew Beckenbach
Keyword(s):  
Sex Ratio ◽  
Drosophila Pseudoobscura ◽  
Experimental Populations ◽  
Fitness Analysis

scholarly journals Genetic divergence in M. Vetukhiv's experimental populations of Drosophila pseudoobscura 1. Rudiments of sexual isolation

1964 ◽  
Vol 5 (1) ◽  
pp. 150-157 ◽  
Author(s):  
Lee Ehrman
Keyword(s):  
Genetic Divergence ◽  
Sexual Isolation ◽  
Drosophila Pseudoobscura ◽  
Selection For ◽  
Experimental Populations

Weak but statistically significant sexual isolation has been demonstrated among Vetukhiv's six experimental populations of Drosophila pseudoobscura, all originally descended from founders taken from cultures of the same hybrids from four geographic localities. These six populations were maintained separately for almost 4½ years and then tested for the existence of sexual isolation. The sexual isolation has arisen in the absence of any selection for isolation, evidently as a by-product of genetic divergence.

scholarly journals Sex ratios in natural populations of Drosophila pseudoobscura from Mexico

Genetika ◽  
2012 ◽  
Vol 44 (3) ◽  
pp. 491-498 ◽  
Author(s):  
Victor Salceda ◽  
Carolina Arceo-Maldonado
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Natural Populations ◽  
Diploid Species ◽  
Drosophila Pseudoobscura ◽  
Adult Offspring ◽  
Equal Proportion ◽  
X Chromosomes ◽  
The Individual ◽  
Number Of Males

Most species show an equal proportion of individuals of both sexes. In diploid species sex ratio is determined by a genic balance between sex chromosomes. In Drosophila sex is determined by the ratio of X- chromosomes versus autosomes and in some species of the genus it is related to the presence of an inversion in the sex chromosome. The present work analyses the sex ratio in 27 natural populations of Drosophila pseudoobscura that inhabit Mexico. Female flies captured in nature were counted and their sex ratio calculated and been called generation P, then cultured individualy, allowed to leave adult offspring which was quantified in order to get its sex ratio and designated generation F1. sex ratio was calculated using the expression: number of males times 100 divided by the number of females proposed by Darwin (1871). The sex ratio of each population was taken using the average of all the individual counts from each sample. The values found varied among different generations and populations, so for generation P their values varieded 37.4 to 190.4 and in generation F1 from 31.3 up to 96.4 males for each 100 females. According to their geographical distribution four North to South transects were arranged and in them means varied from 60.8 to 81.7 males for each 100 females. All this means that in Mexican population are more females than males, exceptionally more males than females.

EVIDENCE FOR EXTENSIVE GENETIC DIFFERENTIATION BETWEEN THE SEX-RATIO AND THE STANDARD ARRANGEMENT OF DROSOPHILA PSEUDOOBSCURA AND D. PERSIMILIS AND IDENTIFICATION OF HYBRID STERILITY FACTORS

Genetics ◽  
1983 ◽  
Vol 105 (1) ◽  
pp. 71-86
Author(s):  
Chung-I Wu ◽  
Andrew T Beckenbach
Keyword(s):  
Sex Ratio ◽  
Genetic Differentiation ◽  
Genetic Background ◽  
Hybrid Sterility ◽  
Strong Support ◽  
Meiotic Drive ◽  
Complete Loss ◽  
Drosophila Pseudoobscura ◽  
Drosophila Persimilis ◽  
Standard Arrangement

ABSTRACT This study deals with sex-ratio genes tightly linked within the Sex-Ratio inversion. By taking advantage of the fact that the Sex-Ratio chromosome of Drosophila persimilis [SR(B)] is homosequential to the Standard chromosome of D. pseudoobscura [ST(A)], we carried out two reciprocal introgression experiments. Individual segments of SR(B) or ST(A) were introgressed into the genome of D. pseudoobscura or D. persimilis, respectively. Males possessing a hybrid SR(B)-ST(A) X chromosome and a genetic background derived from either of the two species were tested for fertility and sex-ratio expression.—It was found that, in terms of the meiotic drive genes, the Sex-Ratio chromosome differs extensively from the Standard chromosome. Because recombinations of these genes result in a complete loss of sex-ratio expression, this finding lends strong support to the hypothesis of gene coadaptation. Coadaptation, in this context, is the advantage of being transmitted preferentially. In light of this finding, the evolution of the sex-ratio system in these two sibling species is discussed.—Introgression experiments also yielded information about hybrid sterility. With reciprocal introgression, sterility interactions were found to be "asymmetric." The asymmetry is fully expected from the viewpoint of evolution of postmating reproductive isolation.

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