scholarly journals Population Genetics of Drosophila ananassae: Evidence for Population Sub-Structuring at the Level of Inversion Polymorphism in Indian Natural Populations

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Bashisth Narayan Singh ◽  
Pranveer Singh
2007 ◽  
Vol 89 (4) ◽  
pp. 191-199 ◽  
Author(s):  
PRANVEER SINGH ◽  
B. N. SINGH

SummaryThe present study, which is one of the longest temporal (two decades) and largest spatial (different parts of India covered) investigations on inversion polymorphism in natural populations of D. ananassae, was undertaken to understand the dynamics of inversion polymorphism in a broad and comprehensive manner. Forty-five natural populations from different ecogeographic regions of the country (covering the regions from Kashmir to Kanniyakumari and Gujarat to Nagaland) were analysed for chromosomal inversions. All the populations show the presence of the three cosmopolitan inversions, frequencies of which vary among the populations analysed. Simple correlations between frequencies of different inversions and regression analysis of inversion frequencies with latitude, longitude and altitude were insignificant. This reinforces the concept of rigid polymorphism in D. ananassae. Genetic divergence (spatial and temporal) at the level of chromosomal polymorphism among natural populations was calculated. Results show spatial divergence but no temporal divergence. Rigid polymorphic systems of D. ananassae did not show long-term directional trends. On the basis of the present study, and after including comparisons with the studies conducted more than two decades ago, the most important conclusion to be drawn is that the three cosmopolitan inversions in D. ananassae segregate within populations at fairly similar frequencies, and the general geographic pattern has remained constant.


2015 ◽  
Vol 25 (1) ◽  
pp. 42-66 ◽  
Author(s):  
Benjamin A. Wilson ◽  
Nandita R. Garud ◽  
Alison F. Feder ◽  
Zoe J. Assaf ◽  
Pleuni S. Pennings

Genetics ◽  
1975 ◽  
Vol 80 (2) ◽  
pp. 375-394
Author(s):  
C F Wehrhahn

Abstract Most of the models of population genetics are not realistic when applied to data on electrophoretic variants of proteins because the same net charge may result from any of several amino acid combinations. In the absence of realistic models they have, however, been widely used to test competing hypotheses about the origin and maintenance of genetic variation in populations. In this paper I present a general method for determining probability generating functions for electrophoretic state differences. Then I use the method to find allelic state difference distributions for selectively similar electrophoretically detectable alleles in finite natural populations. Predicted patterns of genetic variation, both within and among species, are in reasonable accord with those found in the Drosophila willistoni group by Ayala et al. (1972) and by Ayala and Tracey (1974).


1990 ◽  
Vol 36 ◽  
pp. 567-579 ◽  

Sewall Wright's active life spanned the development of genetics from a new discipline when the principles of inheritance were still being elucidated to the technology of recombinant gene construction and insertion. He was one of the major pioneers of population genetics, which gave a quantitative basis to the studies of evolution, of variation in natural populations and of animal and plant breeding. He contributed most significantly to methods and ideas over a long period, indeed his four volume treatise was written long after he formally ‘retired’ and his last paper (211) was published a few days before his death at the age of 98. In the field of population genetics Wright developed the method of path coefficients, which he used to analyse quantitative genetic variation and relationship, but which has been applied to subjects as diverse as economics, the ideas of inbreeding coefficient and F -statistics which form the basis of analysis of population structure, the theory of variation in gene frequency among populations, and the shifting balance theory of evolution, which remains a topic of active research and controversy. Wright contributed to physiological genetics, notably analysis of the inheritance of coat colour in the guinea pig, and in particular the epistatic relationships among the genes involved. There was a critical interplay between his population and physiological work, in that the analysis of finite populations on the one hand and of epistatic interactions on the other are the bases of Wright’s development of the shifting balance theory. A full and enlightening biography of Sewall Wright which traces his influence on evolutionary biology and his interactions with other important workers was published recently (Provine 1986) and shorter appreciations have appeared since his death, notably by Crow (1988), Wright’s long-time colleague. This biography relies heavily on Provine’s volume, and does no more than summarize Wright’s extensive contributions. Many of his important papers have been reprinted recently (1986).


Much has been learned about transposable genetic elements in Drosophila , but questions still remain, especially concerning their evolutionary significance. Three such questions are considered here, (i) Has the behaviour of transposable elements been most influenced by natural selection at the level of the organism, the population, or the elements themselves? (ii) How did the elements originate in the genome of the species? (iii) Why are laboratory stocks different from natural populations with respect to their transposable element composition? No final answers to these questions are yet available, but by focusing on the two families of hybrid dysgenesis-causing elements, the P and I factors, we can draw some tentative conclusions.


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