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Gamete Signalling Underlies the Evolution of Mating Types and Their Number

Summary

This research explores why sex requires two different mating types or sexes, even in single-celled organisms where the reproductive cells look identical. The study shows that having two different types helps cells communicate more efficiently during mating through asymmetric signaling systems. This is similar to having a designated speaker and listener in a conversation, rather than both parties trying to speak and listen simultaneously. Impacts on everyday life: – Provides fundamental understanding of why sex requires two partners – Helps explain the evolution of male and female sexes from simple beginnings – Offers insights for reproductive biology and fertility research – Demonstrates how mathematical modeling can explain complex biological phenomena – Advances our knowledge of cellular communication systems

Background

Sexual reproduction requires two parents, but there is no obvious need for them to be differentiated into distinct mating types or sexes. Yet this is the predominant state of nature, from complex organisms down to single-celled eukaryotes. While complex organisms show clear male/female differentiation, unicellular protists mostly have morphologically identical (isogamous) gametes that are nonetheless divided into distinct mating types that mate disassortatively.

Objective

To explore the hypothesis that mating types evolved due to the need for asymmetric signalling interactions between mating partners. The study examines how signalling asymmetry enhances mating efficiency and develops a mathematical model to understand how the strength of signalling interactions affects mating type evolution and numbers.

Results

The review revealed that asymmetric signalling between mating types is universal across isogamous species, controlling processes from initial sexual differentiation through fusion and post-fusion development. The mathematical model showed that new mating types can only invade if they interact strongly with existing types. If two mating types evolve strong mutual interactions, this can prevent invasion by new types. The model predicts that multiple mating types are only stable when specialization does not restrict interactions with novel types.

Conclusion

The study proposes that the strength of pairwise signalling interactions between gametes is a key factor determining mating type numbers. This provides a novel explanation for why most species have two mating types while some have evolved multiple types. The model accounts for both the predominance of two mating types and the conditions allowing multiple mating type systems.
  • Published in:Philosophical Transactions of the Royal Society B: Biological Sciences,
  • Study Type:Review and Mathematical Modeling,
  • Source: 10.1098/rstb.2015.0531
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