Extinction in relation to demographic and environmental stochasticity in age-structured models

Area of Science:

• Ecology
• Population Dynamics
• Mathematical Biology

Background:

• Demographic variance is crucial for understanding population dynamics and stability.
• Age-structured populations exhibit complex dynamics influenced by vital rates (survival, fecundity).
• Stochasticity, both environmental and demographic, significantly impacts population persistence.

Purpose of the Study:

• To define and decompose demographic variance in age-structured populations.
• To investigate the approximation of age-structured population dynamics by diffusion processes.
• To estimate demographic variance and its components for the wandering albatross.

Main Methods:

• Defining demographic variance and its decomposition into vital rate components.
• Utilizing projection matrices to compute deterministic growth rates.
• Applying diffusion approximations with parameters including deterministic growth rate, environmental variance, and demographic variance.
• Estimating demographic variance and age-specific contributions for a long-lived bird species.

Main Results:

• Demographic variance can be precisely determined by vital rates in specific population models.
• The study provides a method to approximate age-structured population dynamics using a three-parameter diffusion model.
• Estimates of demographic variance and age-specific contributions from survival, fecundity, and their covariance were obtained for the wandering albatross.

Conclusions:

• The defined demographic variance and its components offer a robust framework for analyzing population dynamics.
• Diffusion approximations provide a valuable tool for studying age-structured populations, especially when detailed data is limited.
• Understanding age-specific contributions to demographic variance is essential for conservation and management of long-lived species like the wandering albatross.