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Updated: Jul 4, 2026
13:47
Chromatin Immunoprecipitation (ChIP) using Drosophila tissue
Published on: March 23, 2012
Positive and negative selection on noncoding DNA in Drosophila simulans.
Penelope R Haddrill1, Doris Bachtrog, Peter Andolfatto
1Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom. p.haddrill@ed.ac.uk
Molecular Biology and Evolution
|June 3, 2008
Summary
In Drosophila simulans, noncoding DNA evolution is primarily driven by negative selection, not positive selection as previously suggested for Drosophila melanogaster. This finding clarifies the role of selection in noncoding genome evolution.
Area of Science:
- Evolutionary biology
- Genomics
- Population genetics
Background:
- Noncoding genomic regions are crucial and under selective constraint, especially in Drosophila.
- Previous studies suggested positive selection in noncoding DNA of Drosophila melanogaster.
- Drosophila melanogaster may have a reduced effective population size (N(e)) compared to Drosophila simulans, impacting selection efficacy.
Purpose of the Study:
- To investigate evolutionary patterns in noncoding DNA of Drosophila simulans.
- To determine if negative or positive selection drives noncoding DNA divergence in D. simulans.
- To assess the influence of synonymous site selection and demography on noncoding DNA evolution.
Main Methods:
- Analysis of polymorphism and divergence patterns in various noncoding DNA classes in D. simulans.
- Examination of frequency spectrum skew toward rare variants.
- Comparison of noncoding DNA evolution with synonymous site substitution patterns and demographic models.
Main Results:
- All examined noncoding DNA in D. simulans shows signatures of negative selection (reduced polymorphism/divergence, rare variant skew).
- Purifying selection on synonymous codon usage partially masks negative selection signals in noncoding DNA and nonsynonymous sites.
- Inferred divergence excess in noncoding DNA and nonsynonymous sites is difficult to explain by demographic factors alone.
Conclusions:
- Noncoding DNA in D. simulans is predominantly shaped by negative selection.
- Previous inferences of positive selection in noncoding DNA may be influenced by synonymous site selection and demographic history.
- The study highlights the importance of considering multiple evolutionary forces when interpreting noncoding genome evolution.
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