To Prosper, Live Long: Understanding the Sources of Reproductive Skew and Extreme Reproductive Success in Structured...

Area of Science:

• Ecology
• Evolutionary Biology
• Population Dynamics

Background:

• Reproductive skew is common in many species, with a few individuals producing most offspring.
• Understanding the drivers of reproductive skew and exceptional lifetime reproductive output (LRO) is crucial for population dynamics.
• Previous studies partitioned LRO variance; this study partitions LRO skewness itself.

Purpose of the Study:

• To partition LRO skewness into contributions from fixed traits, demographic luck, and environmental luck.
• To identify the factors contributing to exceptional LRO.
• To understand the relationship between LRO and lifespan.

Main Methods:

• Developed a framework to partition LRO skewness.
• Categorized contributions into fixed trait variation, demographic luck (birth state, fecundity, survival, growth), and environmental luck (birth environment, environment trajectory).
• Analyzed contributions at different ages.

Main Results:

• Reproductive skew is primarily driven by random variation in lifespan.
• Exceptional LRO generally results from an exceptional lifespan.
• Demographic and environmental luck often reduce skewness, except in specific conditions.

Conclusions:

• Lifespan is the dominant factor in reproductive skew and exceptional LRO.
• Environmental conditions can influence fecundity, providing an alternative route to high LRO.
• LRO may not always predict lifespan, especially when environmental factors strongly affect reproduction.