Life Cycle Simplifications in Aphids Drive Changes in Evolutionary Rates and Selection Regimes

Area of Science:

• Evolutionary biology
• Genomics
• Molecular evolution

Background:

• Aphids exhibit complex life cycles involving host alternation (heteroecy) or simplified cycles (monoecy).
• The impact of life cycle simplification on the rate of molecular evolution is not well understood.

Purpose of the Study:

• To investigate how transitions from heteroecy to monoecy affect evolutionary dynamics at the gene level in aphids.
• To determine if life cycle simplification alters selection pressures on genes.

Main Methods:

• Comparative genomics analysis of 46 aphid species.
• Identification of 9,304 orthologs.
• Estimation of evolutionary rates (dN/dS) and selection regimes.

Main Results:

• 715 orthologs showed faster evolution in monoecious species, linked to relaxed selection.
• Heteroecious species displayed signatures of intensified selection.
• Genes under relaxed selection in monoecious species are involved in environmental sensing, signaling, and host alternation traits.

Conclusions:

• Loss of complex life cycles in aphids leads to reduced selective constraints and ecological simplification.
• Life cycle transitions significantly shape molecular evolution and can drive gene decay.