The evolution of life cycle complexity in aphids: Ecological optimization or historical constraint?

Area of Science:

• Evolutionary Biology
• Ecology
• Parasitology

Background:

• Many parasites exhibit obligate multihost life cycles, a phenomenon debated by biologists for decades.
• Understanding the evolutionary drivers of life cycle complexity is crucial for ecological and evolutionary studies.

Purpose of the Study:

• To investigate the roles of ecological optimization and historical constraint in the evolution of complex life cycles in aphids.
• To determine if life cycle complexity is adaptive and evolutionarily labile in response to selection.

Main Methods:

• Comparative phylogenetic analyses of aphid species.
• Evaluation of the relationship between life cycle complexity and traits like polyphagy, reproductive mode, and host breadth.

Main Results:

• Life cycle complexity is evolutionarily labile in some aphid groups (aphidines) but not others (nonaphidines).
• Aphidines show a strong link between complex life cycles and polyphagy, while nonaphidines exhibit a strong association with sexual reproduction.
• The adaptiveness of life cycle complexity is lineage-specific across aphids.

Conclusions:

• Life cycle evolution in aphids is tightly linked with other natural history traits, such as host breadth and reproductive strategies.
• The findings suggest that both adaptive and constraint-based mechanisms contribute to the evolution of life cycle complexity in parasites.