The evolution of soldiers in aphids

Area of Science:

• Evolutionary Biology
• Insect Ecology
• Social Insects

Background:

• Aphids exhibit specialized defensive individuals known as soldiers, typically sterile larvae with distinct morphology and behavior.
• Despite parthenogenetic reproduction, soldier production is not universal in aphids, prompting a clonal investment perspective on defense and reproduction.

Purpose of the Study:

• To investigate the evolutionary origins and diversity of soldier production in aphids.
• To explore the ecological factors, such as plant galls and interactions with predators and ants, influencing soldier evolution.
• To propose an optimality model for understanding soldier investment strategies.

Main Methods:

• Phylogenetic analysis of aphid families (Pemphigidae and Hormaphididae) to trace the evolutionary history of soldier production.
• Review and synthesis of existing evidence on soldier-predator and aphid-ant interactions.
• Development of an optimality model for clonal investment in defense versus reproduction.

Main Results:

• Soldier production has evolved independently at least six to nine times and been lost at least once across aphid phylogeny.
• At least four distinct types of aphid soldiers have been identified.
• Plant galls are a significant factor in the evolution of soldier-producing aphid species.

Conclusions:

• The distribution of soldier production suggests multiple independent evolutionary origins, influenced by factors like plant galls and social interactions.
• Further research is needed to understand the proximate mechanisms underlying soldier production in aphids.