Dataset Information

Drift and Directional Selection Are the Evolutionary Forces Driving Gene Expression Divergence in Eye and Brain Tissue of Heliconius Butterflies.

ABSTRACT: Investigating gene expression evolution over micro- and macroevolutionary timescales will expand our understanding of the role of gene expression in adaptation and speciation. In this study, we characterized the evolutionary forces acting on gene expression levels in eye and brain tissue of five Heliconius butterflies with divergence times of ?5-12 MYA. We developed and applied Brownian motion (BM) and Ornstein-Uhlenbeck (OU) models to identify genes whose expression levels are evolving through drift, stabilizing selection, or a lineage-specific shift. We found that 81% of the genes evolve under genetic drift. When testing for branch-specific shifts in gene expression, we detected 368 (16%) shift events. Genes showing a shift toward upregulation have significantly lower gene expression variance than those genes showing a shift leading toward downregulation. We hypothesize that directional selection is acting in shifts causing upregulation, since transcription is costly. We further uncovered through simulations that parameter estimation of OU models is biased when using small phylogenies and only becomes reliable with phylogenies having ? 50 taxa. Therefore, we developed a new statistical test based on BM to identify highly conserved genes (i.e., evolving under strong stabilizing selection), which comprised 3% of the orthoclusters. In conclusion, we found that drift is the dominant evolutionary force driving gene expression evolution in eye and brain tissue in Heliconius Nevertheless, the higher proportion of genes evolving under directional than under stabilizing selection might reflect species-specific selective pressures on vision and the brain that are necessary to fulfill species-specific requirements.

SUBMITTER: Catalan A

PROVIDER: S-EPMC6781903 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Drift and Directional Selection Are the Evolutionary Forces Driving Gene Expression Divergence in Eye and Brain Tissue of <i>Heliconius</i> Butterflies.

Catalán Ana A Briscoe Adriana D AD Höhna Sebastian S

Genetics 20190829 2

Investigating gene expression evolution over micro- and macroevolutionary timescales will expand our understanding of the role of gene expression in adaptation and speciation. In this study, we characterized the evolutionary forces acting on gene expression levels in eye and brain tissue of five <i>Heliconius</i> butterflies with divergence times of ∼5-12 MYA. We developed and applied Brownian motion (BM) and Ornstein-Uhlenbeck (OU) models to identify genes whose expression levels are evolving t ...[more]

PMID: 31467133

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Project description:BACKGROUND:A key to understanding the origins of species is determining the evolutionary processes that drive the patterns of genomic divergence during speciation. New genomic technologies enable the study of high-resolution genomic patterns of divergence across natural speciation continua, where taxa pairs with different levels of reproductive isolation can be used as proxies for different stages of speciation. Empirical studies of these speciation continua can provide valuable insights into how genomes diverge during speciation. METHODS:We examine variation across a handful of genomic regions in parapatric and allopatric populations of Heliconius butterflies with varying levels of reproductive isolation. Genome sequences were mapped to 2.2-Mb of the H. erato genome, including 1-Mb across the red color pattern locus and multiple regions unlinked to color pattern variation. RESULTS:Phylogenetic analyses reveal a speciation continuum of pairs of hybridizing races and incipient species in the Heliconius erato clade. Comparisons of hybridizing pairs of divergently colored races and incipient species reveal that genomic divergence increases with ecological and reproductive isolation, not only across the locus responsible for adaptive variation in red wing coloration, but also at genomic regions unlinked to color pattern. DISCUSSION:We observe high levels of divergence between the incipient species H. erato and H. himera, suggesting that divergence may accumulate early in the speciation process. Comparisons of genomic divergence between the incipient species and allopatric races suggest that limited gene flow cannot account for the observed high levels of divergence between the incipient species. CONCLUSIONS:Our results provide a reconstruction of the speciation continuum across the H. erato clade and provide insights into the processes that drive genomic divergence during speciation, establishing the H. erato clade as a powerful framework for the study of speciation.

Dataset Information

Drift and Directional Selection Are the Evolutionary Forces Driving Gene Expression Divergence in Eye and Brain Tissue of Heliconius Butterflies.

Publications

Drift and Directional Selection Are the Evolutionary Forces Driving Gene Expression Divergence in Eye and Brain Tissue of <i>Heliconius</i> Butterflies.

Similar Datasets

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