Disparate maturation adaptations to size-dependent mortality.

Area of Science:

• Evolutionary biology
• Life-history theory
• Population dynamics

Background:

• Body size is a key factor influencing an organism's resource use, reproductive success (fecundity), and risk of death (mortality risk).
• Life-history theory posits that maturation size evolves in response to size-dependent selection, with predictions suggesting increased mortality in smaller individuals leads to larger maturation sizes.

Purpose of the Study:

• To investigate the complex evolutionary responses of maturation size to size-dependent mortality.
• To challenge existing predictions regarding the adaptive evolution of maturation size under varying mortality pressures.

Main Methods:

• Utilized a continuously size-structured mathematical model.
• Simulated scenarios with size-dependent mortality, indeterminate growth, reproduction-impaired growth, and size-dependent fecundity.

Main Results:

• Demonstrated that increased mortality among small individuals can result in three alternative evolutionary outcomes for maturation size: an increase, a decrease, or evolutionary bistability.
• Revealed that adaptive responses to altered size-dependent mortality are complex and cannot be predicted by simple directional changes.

Conclusions:

• The evolution of maturation size under size-dependent mortality is more intricate than previously assumed.
• Altered size-dependent mortality can reverse adaptive directions and induce abrupt shifts in evolutionarily stable maturation sizes, highlighting the difficulty in predicting evolutionary trajectories.