Stronger Historical Contingency Facilitates Ecological Specializations: An Example with Avian Carotenoid Networks

Area of Science:

• Biochemistry
• Evolutionary Biology
• Systems Biology

Background:

• Understanding how evolutionary processes maintain robust states while allowing transitions is challenging due to the transient nature of evolutionary pathways.
• Carotenoid networks in birds are crucial for adaptation but their evolutionary dynamics are not fully understood.

Purpose of the Study:

• To investigate the biochemical mechanisms underlying evolutionary robustness and transitions in avian carotenoid networks.
• To identify key molecular features that reconcile stability and adaptability in evolutionary systems.

Main Methods:

• Mapping enzymatic interactomes of 260 bird species and ancestral states onto a global, unmodified carotenoid biochemical network.
• Analyzing the structure and properties of carotenoid networks in relation to ecological specialization.

Main Results:

• Degenerate carotenoids, synthesized interchangeably via different pathways, act as evolutionarily stable stepping stones between network states.
• Ecological specialization correlates with fragmented enzymatic networks, but degeneracy restores robustness.
• Accumulation of degenerate carotenoids facilitates direct transitions between ecological specializations and supports evolutionary exploration.

Conclusions:

• Network degeneracy is a key feature that enhances the robustness of specialized enzymatic networks and enables evolutionary transitions.
• This study provides mechanistic insights into the interplay between natural selection and historical contingency in evolution.
• Degenerate carotenoids are critical for sustaining evolutionary novelty and adaptation in avian systems.