Limited Introgression between Rock-Wallabies with Extensive Chromosomal Rearrangements

Area of Science:

• Evolutionary Biology
• Genomics
• Speciation

Background:

• Chromosome rearrangements, especially Robertsonian fusions, are implicated in rapid hybrid incompatibility evolution.
• Rock-wallabies (Petrogale) provide a model system to study Robertsonian fusions in recent speciation events.

Purpose of the Study:

• To investigate the role of Robertsonian fusions and chromosomal rearrangements in the speciation of Australian rock-wallabies using genomic data.
• To resolve divergence histories and assess patterns of introgression among closely related Petrogale species.

Main Methods:

• Extensive population and genome-wide sampling of rock-wallabies from north-eastern Australia.
• Phylogenetic and population genetic analyses utilizing genomic data.
• Comparison of divergence patterns between X-linked and autosomal loci.

Main Results:

• Genomic data successfully differentiated closely related species and resolved their divergence histories, outperforming previous methods.
• Evidence of introgression was found between species differing by a single Robertsonian fusion and those with complex chromosomal rearrangements.
• X-linked loci exhibited higher divergence than autosomal loci, suggesting a role in reproductive isolation alongside chromosomal changes.

Conclusions:

• Robertsonian fusions and structural variations are significant drivers of divergence and speciation in rock-wallabies.
• Genome-scale data are crucial for understanding the impact of chromosomal rearrangements on molecular evolution and reproductive isolation.
• Genic evolution, particularly on X-linked loci, may complement chromosomal evolution in generating reproductive isolation.