Density-dependence interacts with extrinsic mortality in shaping life histories

Area of Science:

• Evolutionary Biology
• Ecology
• Theoretical Biology

Background:

• The influence of extrinsic mortality on life history evolution is not well understood.
• Extrinsic mortality and density-dependence are known to interact significantly in shaping life histories.

Purpose of the Study:

• To develop a theoretical model integrating Evolutionarily Stable Strategies (ESS) with a projection matrix to explore resource allocation.
• To investigate how density-dependence acting on mortality, fecundity, or production rate influences life history traits under varying extrinsic mortality.
• To elucidate the interplay between extrinsic mortality and density-dependence, including any compensation mechanisms.

Main Methods:

• Development of a theoretical model combining ESS with a projection matrix.
• Analysis of three scenarios where density-dependence affects mortality, fecundity, or production rate.
• Simulation and mathematical analysis to assess the impact of density-independent extrinsic mortality on life history traits.

Main Results:

• Density-independent extrinsic mortality affects aging rate, age at maturity, growth rate, and adult size when density-dependence acts on fertility or juvenile mortality.
• Extrinsic mortality has no impact on these life history traits if density-dependence solely affects adult survival.
• A compensation mechanism exists where increased extrinsic mortality reduces density-dependence strength, fully offsetting effects only when density-dependence is age-independent for survival.

Conclusions:

• The interaction between extrinsic mortality and density-dependence is critical for life history evolution.
• The specific type of density-dependence (acting on survival, fecundity, or production) and its age-pattern are key determinants of life history trait evolution.
• Resource allocation to growth, repair, and reproduction is modulated by these density-dependent and density-independent factors.