Gene expression plasticity followed by genetic change during colonization in a high-elevation environment

Area of Science:

• Evolutionary biology
• Genomics
• Physiological adaptation

Background:

• Phenotypic plasticity enables species to colonize new environments.
• The 'plasticity-first' hypothesis suggests initial plastic changes can be later genetically assimilated.
• Understanding gene expression changes during adaptation to novel environments is crucial.

Purpose of the Study:

• To quantify gene expression plasticity and regulatory adaptation in Eurasian Tree Sparrows.
• To investigate how gene expression changes in response to hypoxia are modified during high-elevation colonization.
• To determine the relationship between gene expression plasticity, muscle phenotypes, and genetic divergence.

Main Methods:

• Studied Eurasian Tree Sparrows from lowland (ancestral) and highland (colonized) populations.
• Experimentally induced hypoxia acclimation to assess plastic responses.
• Analyzed gene expression in cardiac and flight muscles, correlating with muscle phenotypes.

Main Results:

• Gene expression plasticity related to hypoxia tolerance was frequently reversed, not reinforced, in colonized populations.
• Maladaptive plasticity (decreasing hypoxia tolerance) was reduced, while adaptive plasticity (increasing hypoxia tolerance) was reinforced.
• Genes with significant reinforcement or reversion showed greater genetic divergence between ancestral and colonized populations.

Conclusions:

• Gene expression plasticity during initial high-elevation colonization can be reversed or reinforced by selection.
• Colonizing populations fine-tune their gene expression to optimize hypoxia tolerance.
• This study highlights the interplay between plasticity and genetic adaptation in evolutionary processes.