scholarly journals Evolutionary programmed development as the basis of Darwinian selection: A review

2009 ◽  
Vol 61 (4) ◽  
pp. 573-579
Author(s):  
D. Marinkovic
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Adult Male ◽  
Basic Problem ◽  
Evolutionary Development ◽  
Allozyme Analysis ◽  
Metabolic System ◽  
Darwinian Selection ◽  
Intrinsic Factors ◽  
Potential Variation

The sources of biological variation are numerous and versatile. The basic problem is to explain how this huge potential variation could be limited and reduced to adaptive combinations of allelogenes and characters. It has been estimated that, in a population of Drosophila melanogaster with a few thousands of individuals, the number of existing genotypes for a metabolic system controlled by 8-10 polymorphic loci, would not exceed more than 0.5% of possible combinations of genes. Based on individual allozyme analysis of such a system in 400 flies, less than 1 pro-mile of possible combinations of three largest chromosomes of this species could be present in spermatozoa of an adult male, before they enter a competition to produce viable zygotes. Such adaptive combinations are targets of natural selection, realized through a restricted number of developmental (metabolic) programmes, being also the units of inheritance. The basic role in evolutionary development of such systems have intrinsic factors, i.e., the rules of auto-synthesis of well established programmes, directing a restrictive variation of adaptive variants with which Darwinian selection can operate.

scholarly journals Selective Constraints on Intron Evolution in Drosophila

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 1843-1851 ◽  
Author(s):  
John Parsch
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Common Ancestor ◽  
Length Distribution ◽  
Short Length ◽  
Intron Length ◽  
Intron Evolution ◽  
Intron Size ◽  
Duplicated Genes ◽  
Selective Constraints

AbstractIntron sizes show an asymmetrical distribution in a number of organisms, with a large number of “short” introns clustered around a minimal intron length and a much broader distribution of longer introns. In Drosophila melanogaster, the short intron class is centered around 61 bp. The narrow length distribution suggests that natural selection may play a role in maintaining intron size. A comparison of 15 orthologous introns among species of the D. melanogaster subgroup indicates that, in general, short introns are not under greater DNA sequence or length constraints than long introns. There is a bias toward deletions in all introns (deletion/insertion ratio is 1.66), and the vast majority of indels are of short length (<10 bp). Indels occurring on the internal branches of the phylogenetic tree are significantly longer than those occurring on the terminal branches. These results are consistent with a compensatory model of intron length evolution in which slightly deleterious short deletions are frequently fixed within species by genetic drift, and relatively rare larger insertions that restore intron length are fixed by positive selection. A comparison of paralogous introns shared among duplicated genes suggests that length constraints differ between introns within the same gene. The janusA, janusB, and ocnus genes share two short introns derived from a common ancestor. The first of these introns shows significantly fewer indels than the second intron, although the two introns show a comparable number of substitutions. This indicates that intron-specific selective constraints have been maintained following gene duplication, which preceded the divergence of the D. melanogaster species subgroup.

scholarly journals GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 569-589
Author(s):  
Martin L Tracey ◽  
Francisco J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Natural Population ◽  
Natural Populations ◽  
Genetic Load ◽  
Structural Genes ◽  
Invertebrate Species ◽  
Average Proportion ◽  
Mean Fitness ◽  
The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

scholarly journals Sexual Selection Does Not Increase the Rate of Compensatory Adaptation to a Mutation Influencing a Secondary Sexual Trait in Drosophila melanogaster

2020 ◽  
Vol 10 (5) ◽  
pp. 1541-1551
Author(s):  
Christopher H. Chandler ◽  
Anna Mammel ◽  
Ian Dworkin
Keyword(s):  
Drosophila Melanogaster ◽  
Sexual Selection ◽  
Natural Selection ◽  
Spontaneous Mutation ◽  
Phenotypic Expression ◽  
Theoretical Work ◽  
Phenotypic Suppression ◽  
Compensatory Adaptation ◽  
Deleterious Alleles ◽  
Sex Comb

Theoretical work predicts that sexual selection can enhance natural selection, increasing the rate of adaptation to new environments and helping purge harmful mutations. While some experiments support these predictions, remarkably little work has addressed the role of sexual selection on compensatory adaptation—populations’ ability to compensate for the costs of deleterious alleles that are already present. We tested whether sexual selection, as well as the degree of standing genetic variation, affect the rate of compensatory evolution via phenotypic suppression in experimental populations of Drosophila melanogaster. These populations were fixed for a spontaneous mutation causing mild abnormalities in the male sex comb, a structure important for mating success. We fine-mapped this mutation to an ∼85 kb region on the X chromosome containing three candidate genes, showed that the mutation is deleterious, and that its phenotypic expression and penetrance vary by genetic background. We then performed experimental evolution, including a treatment where opportunity for mate choice was limited by experimentally enforced monogamy. Although evolved populations did show some phenotypic suppression of the morphological abnormalities in the sex comb, the amount of suppression did not depend on the opportunity for sexual selection. Sexual selection, therefore, may not always enhance natural selection; instead, the interaction between these two forces may depend on additional factors.

Les regressions marines et le probleme du renouvellement des faunes au cours des temps geologiques

1964 ◽  
Vol S7-VI (1) ◽  
pp. 13-22 ◽  
Author(s):  
L. Ginsburg
Keyword(s):  
Natural Selection ◽  
Evolutionary Development ◽  
Animal Populations ◽  
Chance Occurrence ◽  
Regular Rhythm

Abstract One basis for geochronology is the succession of faunal groups. Evolutionary transformations, the extinction of species, and the appearance of new forms is neither a chance occurrence nor one marked by a regular rhythm. The disequilibrium provoked by alternating transgressions and regressions has a profound effect on animal populations. At the end of each marine regression a hecatomb of fauna is left in the neritic zones. A return of the sea in the succeeding transgression provides opportunity for the multiplication and diversification of the surviving forms. Through this process of natural selection evolutionary development is stimulated by alternating marine cycles.

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