Museum Skins Enable Identification of Introgression Associated with Cytonuclear Discordance
Sally Potter1,2,3, Craig Moritz2, Maxine P Piggott2,4
1School of Natural Sciences, 14 Eastern Road, Macquarie University, Macquarie Park, NSW 2109, Australia.
Systematic Biology
|April 5, 2024
Summary
Genetic exchange between closely related rock-wallaby species is more common than previously thought, leading to significant cytonuclear discordance. Genomic data reveals ancient introgression, challenging assumptions about gene flow, especially given body size differences.
Area of Science:
- Evolutionary Biology
- Genomics
- Speciation
Background:
- Genetic exchange during and after speciation can be substantial.
- Cytonuclear discordance, where mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) divergence patterns differ, is a key indicator of such exchange.
- Advances in genome-scale data and coalescent modeling enable robust identification of introgression.
Purpose of the Study:
- To investigate complex evolutionary histories in the rock-wallaby (Petrogale brachyotis group) using genomic tools.
- To assess the role of demographic processes and ancient introgression in driving evolutionary patterns.
- To identify instances of cytonuclear discordance and test for historical introgression as a cause.
Main Methods:
- Population and phylogenomic analyses of exon capture data from historical and recent rock-wallaby specimens.
- Coalescent modeling and Approximate Bayesian Computation (ABC) modeling of nuclear gene trees.
- Comparison of divergence patterns between mitochondrial DNA (mtDNA) and nuclear DNA (nDNA).
Main Results:
- Nuclear genes support species monophyly, but mtDNA does not, indicating significant cytonuclear discordance across four species.
- Evidence for introgression during or after speciation was found in some taxon pairs, despite substantial body size differences.
- Introgression patterns were heterogeneous and not linked to chromosomal differences.
Conclusions:
- Ancient introgression and hybridization have played a significant role in the evolutionary history of the brachyotis rock-wallaby group.
- Dynamic past climates in monsoonal tropics may have facilitated reticulation (gene flow) among related species.
- Genomic approaches are powerful for resolving complex evolutionary histories marked by gene flow.
