The evolution of polyembryony in parasitoid wasps

Area of Science:

• Evolutionary biology
• Developmental biology
• Insect ecology

Background:

• Polyembryony, the development of multiple embryos from a single egg, has evolved independently in four parasitoid wasp families.
• Understanding the selective pressures driving this reproductive strategy is crucial for insect evolutionary studies.

Purpose of the Study:

• To review and evaluate the main hypotheses for the evolution of polyembryony in parasitoid wasps.
• To assess the relative importance of different selective forces across evolutionary stages and wasp groups.

Main Methods:

• Comparative data analysis.
• Verbal arguments.
• Mathematical modeling.

Main Results:

• Reducing the costs of egg limitation is a key factor, particularly when large broods are advantageous.
• Minimizing genetic conflict among offspring may have been critical during the initial evolutionary transition to polyembryony, especially for smaller broods.
• Empirical evidence for brood-size adjustment to host quality is limited, suggesting it plays a secondary or interactive role.

Conclusions:

• The evolution of polyembryony in parasitoid wasps is driven by a combination of factors, with egg limitation costs and genetic conflict playing significant roles.
• The relative importance of these factors varies with brood size and evolutionary context.
• Future research should explore the interplay between brood-size adjustment and other selective forces.