Genomic parallelism defines repeated evolution of an inducible offense

Area of Science:

• Evolutionary biology
• Developmental biology
• Genetics

Background:

• Resource competition is a key driver of evolutionary change.
• Polyphenism, the development of alternative phenotypes, can be an extreme response to competition.
• The evolution of polyphenism in response to ecological challenges like predation is not well understood.

Purpose of the Study:

• To investigate the evolution of facultative predation and predatory morph induction in nematodes under resource competition.
• To determine the genetic basis and generalizability of these adaptive changes.
• To understand how polyphenism evolves under selective pressures.

Main Methods:

• Replicated experimental evolution with starved nematodes allowed to prey on competitors.
• Artificial selection directly on tooth morphology to compare with evolutionary outcomes.
• Genomic analysis to identify parallel genetic changes across populations.

Main Results:

• Fifty generations of evolution led to parallel increases in morph induction and genomic changes, including selection for a transcription-factor binding-site variant.
• Direct selection on tooth morphology resulted in faster evolution of the predatory morph than experimental evolution.
• Polyphenism evolution appears balanced by selection for overall organism performance.

Conclusions:

• The evolution of resource-driven polyphenism is predictable under conditions of scarce resources.
• Genetic and phenotypic changes underlying polyphenism can evolve in parallel.
• Selection on specific traits can be a powerful driver, but whole-organism performance influences the balance of evolutionary change.