Direct Gamete Sequencing Reveals No Evidence for Segregation Distortion in House Mouse Hybrids

Area of Science:

• Evolutionary genetics
• Speciation research
• Reproductive isolation mechanisms

Background:

• Dobzhansky-Muller incompatibilities are key to postzygotic reproductive isolation between diverging species.
• The evolutionary drivers accumulating these incompatibilities remain largely unknown.
• Segregation distorters are suspected contributors to Dobzhansky-Muller incompatibilities in some taxa.

Purpose of the Study:

• To investigate the role of segregation distorters in hybrid male infertility between closely related rodent subspecies.
• To test if selfish genetic elements contribute to early-stage reproductive isolation in Mus musculus.

Main Methods:

• Collected viable sperm from first-generation hybrid male mice (Mus musculus castaneus x M. m. domesticus).
• Genotyped millions of single nucleotide polymorphisms (SNPs) in pooled gametes.
• Tested for allele frequency skews across the genome to detect segregation distortion.

Main Results:

• Segregation distorters were not found to be significant contributors to hybrid male infertility.
• The study possessed high statistical power to detect even weak segregation distortion.
• Reduced fertility in these hybrids is likely caused by evolutionary forces other than segregation distortion.

Conclusions:

• Segregation distorters do not explain the observed hybrid male infertility in early-stage Mus mouse speciation.
• Other evolutionary mechanisms are responsible for the accumulation of Dobzhansky-Muller incompatibilities in this system.
• This research refines our understanding of the forces shaping reproductive isolation during speciation.