Do slower movers have lower reproductive success and higher mutation load?

Area of Science:

• Evolutionary biology
• Genetics
• Ecology

Background:

• Deleterious mutations accumulate in populations, potentially leading to extinction.
• Understanding how natural selection counteracts mutation load is crucial for evolutionary dynamics.

Purpose of the Study:

• To investigate selection opportunities on mutation load using manipulative experiments in zebrafish (Danio rerio).
• To assess the direct and indirect responses to selection on locomotor performance and reproductive success.

Main Methods:

• Induced high mutation load in zebrafish through mutagenesis.
• Applied one generation of within-family selection on locomotor performance.
• Characterized direct response (swimming speed) and indirect response (reproductive success).

Main Results:

• Offspring of slow-swimming parents showed age-dependent declines in swimming speed, unlike offspring of fast-swimming parents.
• Reproductive success was significantly lower in crosses among slow-swimming fish offspring.
• Selection appears to act on mutation number per se, affecting embryo viability rather than solely lethal recessive homozygotes.

Conclusions:

• Selection can act concurrently on different fitness components to reduce mutation load.
• Early life mortality plays a significant role in removing deleterious mutations.
• Accurate assessment of evolutionary dynamics requires accounting for early life mortality.