Trading stages: life expectancies in structured populations

Area of Science:

• Biodemography
• Population Ecology
• Mathematical Biology

Background:

• Age-structured demographic models traditionally exclude quantitative traits like size.
• Stage-structured models are valuable for traits like size but lack accessible analysis tools for vital rates' impact on lifespan.
• Existing methods for analyzing vital rates in stage-structured populations are complex and difficult to interpret.

Purpose of the Study:

• To develop easily interpretable expressions for sensitivities and elasticities of life expectancy to vital rates in age-stage structured population models.
• To provide practical tools for the analysis of age- and stage-structured populations.
• To advance the framework for studying age- and stage-structured biodemography.

Main Methods:

• Derivation of novel, interpretable expressions for life expectancy sensitivities and elasticities in age-stage models.
• Application of these methods to two distinct biological examples.
• Utilizing a conceptual framework based on the trade-off between time and mortality risk across different life stages.

Main Results:

• Successfully derived user-friendly expressions for analyzing the impact of vital rates on life expectancy in age-stage structured populations.
• Demonstrated the practical utility and interpretability of the new methods through biological case studies.
• Provided a foundation for a more comprehensive understanding of biodemographic dynamics in structured populations.

Conclusions:

• The developed methods enhance the interpretability and usability of vital rate analyses in age-stage structured population models.
• This work contributes to a new framework for biodemographic studies, integrating age and stage structure.
• The findings facilitate a deeper understanding of how demographic rates influence lifespan in populations with complex life histories.