Contrasting Evolutionary Patterns Between Sexual and Asexual Lineages in a Genomic Region Linked to Reproductive Mode...

Area of Science:

• Evolutionary Biology
• Genetics
• Reproductive Biology

Background:

• Asexual lineages frequently evolve from sexual ancestors across diverse taxa.
• The genetic underpinnings of sex loss remain largely uncharacterized.
• Pea aphids (Acyrthosiphon pisum) offer a model system with both cyclical parthenogenesis (CP) and obligate parthenogenetic (OP) lineages.

Purpose of the Study:

• To investigate the genetic basis of reproductive mode variation in pea aphids.
• To identify genomic regions associated with the transition from sexual to asexual reproduction.

Main Methods:

• Whole-genome scanning using single nucleotide polymorphism (SNP) data.
• Sequencing of pooled DNA from multiple populations representing CP and OP lineages.
• Analysis of genetic differentiation (FST) and diversity metrics (Tajima's D).

Main Results:

• An 840-kb region on the X chromosome is strongly associated with reproductive mode variation.
• This X-linked region exhibits high divergence (FST = 34.9%) between CP and OP populations.
• OP populations show reduced genetic diversity and Tajima's D in this region, suggesting it is a derived trait.

Conclusions:

• The identified X-linked region is a key factor in the evolution of obligate parthenogenesis in pea aphids.
• Low genome-wide differentiation suggests ongoing gene flow between CP and OP lineages.
• Climate-driven selection and genetic exchange likely maintain both reproductive strategies.