Clock gene evolution: seasonal timing, phylogenetic signal, or functional constraint?

Area of Science:

• Evolutionary biology
• Genetics
• Ecology

Background:

• Understanding the genetic basis of seasonal reproduction is crucial for predicting species' responses to climate change.
• Circadian rhythm genes, like Clock1a, play a role in timing biological events, including reproduction.

Purpose of the Study:

• To investigate the relationship between allelic length variation in the Clock1a gene and seasonal reproductive timing in cyprinid fishes.
• To explore the evolutionary history of Clock1a variation within a fish community.

Main Methods:

• Comparative analysis of Clock1a gene allelic length variation across 6 cyprinid species (5 native, 1 introduced) in the Rio Grande.
• Assessment of phylogenetic signal and heterozygosity in Clock1a across species.
• Correlation analysis between Clock1a allele length and reproductive timing.

Main Results:

• Longer Clock1a common allele lengths were associated with earlier initiation of reproduction in native species.
• Clock1a allele length showed a strong phylogenetic signal, with earlier spawners being evolutionarily derived.
• The endangered Rio Grande silvery minnow exhibited significantly lower allelic variation and heterozygosity in Clock1a compared to nonimperiled species.

Conclusions:

• Allelic length variation in Clock1a is a significant factor differentiating seasonal reproductive timing in cyprinid fishes.
• Reduced genetic variation in Clock1a for the Rio Grande silvery minnow may hinder its adaptive capacity to environmental changes, including climate change.