Relaxed selection is a precursor to the evolution of phenotypic plasticity
Brendan G Hunt1, Lino Ometto, Yannick Wurm
1School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Summary
Phenotypic plasticity allows organisms to adapt, but its link to molecular evolution is unclear. Genes for plastic traits in fire ants evolved rapidly, but surprisingly, caste-related genes evolved quickly even without castes, suggesting relaxed selection drives plasticity.
Area of Science:
- Evolutionary biology
- Molecular evolution
- Genomics
Background:
- Phenotypic plasticity enables adaptive responses to environmental changes.
- The interplay between phenotypic plasticity and molecular evolution requires further investigation.
- Understanding gene evolution in plastic traits is crucial for evolutionary biology.
Purpose of the Study:
- To investigate the evolutionary rates of genes associated with phenotypic plasticity in the fire ant Solenopsis invicta.
- To determine if genes involved in plastic traits evolve faster than constitutively expressed genes.
- To explore the evolutionary history of caste-biased genes and their relationship with plasticity.
Main Methods:
- Comparative genomic analysis of Solenopsis invicta.
- Analysis of gene expression patterns across castes, sexes, and developmental stages.
- Phylogenetic analysis of orthologous genes in related species.
Main Results:
- Genes associated with phenotypic plasticity (castes, sexes, developmental stages) in S. invicta showed accelerated rates of molecular evolution.
- Orthologs of caste-biased genes in S. invicta and Apis mellifera evolved rapidly even in lineages lacking castes.
- Elevated evolutionary rates were not solely a consequence of phenotypic plasticity itself.
Conclusions:
- Rapid molecular evolution may not primarily result from phenotypic plasticity.
- Relaxed purifying selection on protein-coding genes facilitates the evolution of biased gene expression and phenotypic plasticity.
- Relaxed selective constraint is a key, underappreciated factor in the origin of phenotypic plasticity.
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