THE EFFECTIVE SIZE OF A HIERARCHICALLY STRUCTURED POPULATION.

Area of Science:

• Population Genetics
• Evolutionary Biology
• Quantitative Genetics

Background:

• Effective population size (N_e) is a fundamental parameter for assessing evolutionary potential.
• Hierarchically structured populations often exhibit N_e values that deviate from simple additive models.
• Inbreeding, quantified by F_IS (within-population) and F_ST (between-population), significantly influences N_e.

Purpose of the Study:

• To link effective population size (N_e) to hierarchical measures of inbreeding (F_IS, F_ST) in island-structured populations.
• To investigate the impact of island productivity regulation on the relationship between inbreeding and N_e.
• To explore how non-ideal factors, such as unequal sex ratios and variance in reproductive success, affect N_e.

Main Methods:

• Theoretical modeling of island-structured populations (metapopulations).
• Analysis of two models: interdemic (no local regulation) and traditional island model (equal productivity).
• Incorporation of non-ideal factors: sex ratio, variance in reproductive success, and mating systems.

Main Results:

• Under the interdemic model, both F_IS and F_ST reduce N_e, with N_e = N_T /[(1 + F_IS )(1 + F_ST ) - 2F_IS F_ST].
• Under the island model, F_ST's effect is reversed, leading to N_e = N_T /[(1 + F_IS )(1 -F_ST )].
• Habitat quality variation and non-ideal factors (sex ratio, reproductive variance) consistently decrease N_e.

Conclusions:

• Island productivity regulation critically determines the influence of F_ST on N_e.
• Spatial heterogeneity and non-ideal demographic factors significantly reduce effective population size.
• Accurate estimation of F_IS and F_ST is essential for applying these population genetic models.