Digest: Extremes of the mating system continuum are the most evolutionarily stable

Area of Science:

• Evolutionary Biology
• Ornithology
• Behavioral Ecology

Background:

• Understanding the evolutionary stability of avian mating systems is crucial for comprehending bird diversification.
• Previous research has explored various factors influencing mating system evolution, but macroevolutionary perspectives on stability are less common.

Purpose of the Study:

• To investigate the macroevolutionary stability of different avian social mating systems.
• To determine if resource-defense polygamy and lek polygamy exhibit varying evolutionary trajectories compared to monogamy.

Main Methods:

• Macroevolutionary comparative analysis of bird social mating systems.
• Phylogenetic methods to reconstruct evolutionary transitions between mating systems (monogamy, resource-defense polygamy, lek polygamy).

Main Results:

• Resource-defense polygamy is a macroevolutionarily unstable mating system, frequently transitioning to monogamy or extinction.
• Lek polygamy demonstrates significant evolutionary stability, comparable to that of monogamy.
• Monogamy and lek polygamy involve different parental investment strategies, with monogamy characterized by equal investment and lek systems by sex-specific optimization.

Conclusions:

• The findings challenge assumptions about the stability of polygamous systems, highlighting resource-defense polygamy as a transient evolutionary phase.
• Lek polygamy represents a stable alternative mating system in birds, driven by independent fitness maximization strategies for each sex.
• Evolutionary stability of mating systems is influenced by the interplay of social structure, parental care, and sexual selection.