Demographic History Inferred From an Inversion-Rich Spruce Bark Beetle Genome.

Area of Science:

• Evolutionary biology
• Genomics
• Population genetics

Background:

• Demographic history inference from whole-genome data is crucial for understanding species evolution.
• Polymorphic chromosomal inversions can affect genome-wide variation and evolutionary inferences.
• The spruce bark beetle (Ips typographus) genome contains a complex inversion landscape.

Purpose of the Study:

• To reconstruct the demographic history of the spruce bark beetle across Europe.
• To investigate the impact of chromosomal inversions on demographic inference.
• To provide insights into the evolutionary dynamics of this important forest pest.

Main Methods:

• Genome-wide data analysis from over 300 Ips typographus individuals across 23 European populations.
• Application of Pairwise Sequential Markovian Coalescent (PSMC) and Site Frequency Spectrum (SFS)-based modeling.
• Analysis of a complex polymorphic inversion landscape covering approximately 28% of the beetle genome.

Main Results:

• A Late Pleistocene divergence (~79 kya) was identified between southern and northern European populations.
• Southern populations underwent significant expansion post-divergence; northern populations expanded during the Holocene (~7 kya).
• Chromosomal inversions had a minor impact on demographic parameter estimates and model selection.

Conclusions:

• The study elucidates the historical population dynamics of the spruce bark beetle.
• It demonstrates that complex genomic architectures like inversions can be accounted for in demographic inference.
• Findings improve understanding of how genomic structure influences evolutionary history reconstruction.