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The N/N ratio in applied conservation.

Robin S Waples¹

¹School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA.

Evolutionary Applications

|May 9, 2024

Summary

This summary is machine-generated.

Effective population size (N_e) and its ratio to census size (N_e/N) are critical for biodiversity conservation. This review clarifies definitions and estimation methods for N_e and N_e/N, emphasizing practical applications in management.

Keywords:

age structure effective population size genetic drift inbreeding spatial structure

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Area of Science:

Conservation Biology
Population Genetics
Ecology

Background:

International conservation bodies increasingly recognize the importance of effective population size (N_e) and the effective size: census size ratio (N_e/N).
Accurate estimation of these parameters is vital for effective biodiversity management and conservation strategies globally.

Purpose of the Study:

To review and synthesize definitions of effective population size (N_e) and census size (N).
To outline demographic and genetic methods for estimating N_e, N, and their ratio (N_e/N).
To emphasize single-generation estimates of contemporary N_e/N for practical conservation applications.

Main Methods:

Review and synthesis of existing literature on effective population size and census size.
Focus on single-generation estimation of contemporary N_e/N.
Discussion of demographic and genetic estimation techniques.

Main Results:

Clarification of census size (N) definition, recommending 'number of adults alive' for cross-species comparison.
Inbreeding N_e is often simpler and more interpretable than variance N_e for many applications.
Overdispersed variance in offspring number is a primary driver of reduced N_e/N, even with age structure and varying fecundity.

Conclusions:

Distinguishing between effective size per generation (N_e) and effective number of breeders per season (N_b) is crucial for age-structured populations.
Both N_e and N_b are important metrics for applied conservation and management.
Factors like lifetime reproductive success variance, mating systems, and population structure influence N_e and require consideration in conservation planning.