Testing the evolutionary theory of inversion polymorphisms in the yellow monkeyflower (Mimulus guttatus)

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Chromosomal inversions are known to influence various natural phenomena.
• Their precise contribution to standing genetic variation remains an open question.
• Understanding inversion dynamics is key to comprehending evolutionary processes.

Purpose of the Study:

• To evaluate the contribution of 64 segregating chromosomal inversions to genetic variation in Mimulus guttatus.
• To investigate the role of inversion breakpoints versus coadapted alleles in fitness effects.
• To test evolutionary predictions regarding inversion polymorphisms.

Main Methods:

• Analysis of nucleotide diversity patterns across 64 inversions in Mimulus guttatus.
• Examination of sequence divergence patterns relative to inversion breakpoints.
• Assessment of genetic variation in gene expression in relation to inversion orientations and breakpoints.

Main Results:

• Nucleotide diversity patterns supported predictions related to inversion origin, selection, and gene flow.
• Sequence divergence varied idiosyncratically, not supporting selection at breakpoints.
• Gene expression variation was partitioned between orientations, not concentrated near breakpoints.
• Evidence suggests coadapted allele capture is more significant than breakpoints for fitness.

Conclusions:

• The study confirms several evolutionary predictions for inversion polymorphisms.
• Coadapted allele capture plays a crucial role in the fitness consequences of inversions.
• Synthesizing data across multiple loci is essential for a clear understanding of inversion impacts.