Evolution of Chromosomal Inversions across an Avian Radiation.

Area of Science:

• Genomics
• Evolutionary Biology
• Population Genetics

Background:

• Chromosomal inversions are key drivers of adaptation and speciation.
• Trans-species inversions can indicate balancing selection or incomplete lineage sorting.
• Munia finches (Lonchura) represent a rapidly radiating clade with complex evolutionary history.

Purpose of the Study:

• Identify and characterize large chromosomal inversions in munia finches.
• Investigate the evolutionary origins and maintenance mechanisms of these inversions.
• Determine the role of inversions in adaptation and speciation within the Lonchura genus.

Main Methods:

• Whole-genome resequencing of 176 individuals from 18 munia populations.
• Identification and analysis of large (4–20 Mb) para- and pericentric inversions.
• Application of coalescent theory to infer evolutionary histories and selection pressures.

Main Results:

• Four large inversions were identified, segregating across multiple munia species.
• These inversions predate the radiation of the Lonchura clade.
• Autosomal inversions are maintained by selection along ecogeographic clines, while the sex chromosome inversion shows signatures of positive selection.
• Trans-species status is unlikely due to neutral evolution, supporting selection-driven maintenance.

Conclusions:

• Trans-species inversion polymorphisms play a significant role in munia adaptation and speciation.
• Selection, not neutral processes, best explains the maintenance of these inversions.
• Genomic regions collinear with inversions provide a crucial null model for selection inference.