Dissecting the Transcriptomic Basis of Phenotypic Evolution in an Aquatic Keystone Grazer

Area of Science:

• Evolutionary biology
• Genomics
• Ecology

Background:

• Understanding adaptation requires knowledge of molecular responses to environmental cues.
• Observing evolutionary adaptation involves comparing organismal responses before and after environmental shifts, which is rarely feasible.
• Daphnia serves as a model organism for ecological and genomic studies of adaptation.

Purpose of the Study:

• To link transcriptomic responses and phosphorus (P)-related phenotypic traits in Daphnia under varying P availability.
• To investigate evolutionary conservation and divergence in transcriptional networks between ancient and modern Daphnia genotypes.
• To elucidate the molecular mechanisms underlying phenotypic evolution and adaptation.

Main Methods:

• Utilized Daphnia as an ecological and genomic model.
• Linked transcriptomic data with P-related phenotypic traits under high and low P availability.
• Mapped weighted gene coexpression networks to traits in ancient (600 years old) and modern Daphnia pulicaria from a P-enriched lake.
• Assessed evolutionary conservation and divergence in transcriptional networks of ancient and modern isolates.

Main Results:

• Discovered highly preserved gene networks shared between ancient Daphnia genotypes and their modern descendants.
• Detected clear evidence of transcriptional divergence between evolutionarily separated Daphnia genotypes.
• Demonstrated that phenotypic evolution results from molecular fine-tuning across multiple biological layers.

Conclusions:

• Gene networks in Daphnia exhibit both conservation and divergence over evolutionary timescales.
• Molecular fine-tuning at various levels contributes to phenotypic evolution and adaptation.
• Findings advance the understanding of population persistence during significant environmental shifts.