Multiple paths to the same destination: Influence of gene flow on convergent evolution

Area of Science:

• Evolutionary genetics
• Population genetics
• Molecular ecology

Background:

• Convergent evolution describes the independent evolution of similar traits in distinct lineages.
• Understanding convergent evolution's genetic basis predicts population responses to similar selective pressures.
• Isolated populations offer unique insights into genetic mechanisms, free from widespread gene flow.

Purpose of the Study:

• To investigate the genetic basis of pelvic reduction in three isolated nine-spined stickleback (Pungitius pungitius) populations.
• To determine the extent to which identical-by-descent alleles contribute to convergent evolution in isolated populations.
• To compare the genetic architecture of pelvic reduction in P. pungitius with that in three-spined stickleback (Gasterosteus aculeatus).

Main Methods:

• Quantitative trait loci (QTL) mapping was employed to identify genetic loci associated with pelvic reduction.
• Comparative genetic analysis was performed across three distinct freshwater populations.
• Candidate gene analysis, including the Pitx1 gene, was conducted.

Main Results:

• Pelvic reduction in the studied nine-spined stickleback populations was attributed to mutations at different genetic loci.
• The Pitx1 gene, a known driver of plate reduction in three-spined stickleback, was causative in only one P. pungitius population.
• Independent genetic mutations, rather than fixation of identical-by-descent alleles, underlie pelvic reduction in these isolated populations.

Conclusions:

• Convergent evolution can arise from distinct genetic mechanisms even in isolated populations.
• The genetic architecture of convergent traits can vary significantly across populations and species.
• Studying evolution in the absence of gene flow is crucial for a comprehensive understanding of genetic variation and adaptation.