Genome architecture evolution in an invasive copepod species complex

Area of Science:

• Evolutionary biology
• Genomics
• Ecology

Background:

• Chromosomal fusions are proposed drivers of adaptation, but empirical support is limited.
• The Eurytemora affinis species complex rapidly colonizes new environments, exhibiting salinity tolerance.
• Ion transport genes are crucial for adapting to varying salinity levels.

Purpose of the Study:

• To investigate the role of chromosomal fusions in the adaptive evolution of the Eurytemora affinis species complex.
• To analyze genome-level changes associated with adaptation to different salinities.
• To identify genomic signatures of selection in relation to habitat.

Main Methods:

• Comparative analysis of chromosome-level genome sequences from three Eurytemora affinis sibling species.
• Identification and characterization of chromosomal fusions and their impact on gene organization.
• Genomic scans for signatures of selection in populations from different salinity environments.

Main Results:

• Chromosomal fusions were identified in two sibling species, joining functionally linked ion transport genes near centromeres.
• Genomes show expansions in ion transport gene families, correlating with salinity adaptation.
• Fusion sites, especially centromeres, in invasive species (E. carolleeae, E. gulfia) exhibit significant selection signatures between saline and freshwater populations.

Conclusions:

• Chromosomal fusions contribute to adaptive evolution by repositioning key genes, facilitating rapid adaptation to environmental change.
• Genome architecture evolution, driven by chromosomal fusions, plays a critical role in the ecological success and invasiveness of copepod species.
• This study provides empirical evidence linking chromosomal rearrangements to adaptive evolution in response to environmental heterogeneity.