A dynamical model for the origin of anisogamy

Area of Science:

• Evolutionary biology
• Mathematical modeling
• Population genetics

Background:

• Most multicellular organisms exhibit anisogamy, a stark contrast to the presumed ancestral state of isogamy.
• The evolutionary transition from isogamy to anisogamy remains a significant unresolved question in evolutionary biology.

Purpose of the Study:

• To develop a simple mathematical model explaining the evolution of anisogamy from isogamy.
• To investigate the role of frequency-dependent selection and gamete size in this evolutionary transition.

Main Methods:

• Utilized nonlinear dynamical systems to create a mathematical model of gamete evolution.
• Incorporated frequency-dependent selection through "mean-field coupling," where gamete survival depends on its size relative to the population mean.
• Employed theoretical analysis and numerical simulations to explore model outcomes.

Main Results:

• Demonstrated that mean-referenced competition reliably leads to a stable anisogamous equilibrium.
• Showed that the model can generate anisogamy without assuming pre-existing mating types.
• Confirmed that isogamy can naturally transition to anisogamy through size-based competition.

Conclusions:

• The evolution of anisogamy from isogamy is a probable outcome driven by size-dependent competition.
• Mathematical modeling provides a powerful framework for understanding fundamental evolutionary transitions.
• Frequency-dependent selection, specifically mean-referenced competition, is a key factor in the evolution of sexual reproduction dimorphism.