Relationship between effective and demographic population size in continuously distributed populations

Area of Science:

• Conservation Genetics
• Population Ecology
• Wildlife Management

Background:

• Genetic monitoring offers simultaneous demographic and genetic insights into wild populations.
• Accurate estimation of contemporary effective population size (N_e) is crucial but often uncertain.
• Widespread application of genetic monitoring is limited by challenges in interpreting N_e metrics.

Purpose of the Study:

• To evaluate the temporal stability of the relationship between effective population size (N_e) and demographic population size (N).
• To assess the reliability of N_e as an indicator of N in continuously distributed, dispersal-limited mammal populations.
• To identify conditions under which genetic metrics can effectively inform wildlife monitoring programs.

Main Methods:

• Utilized four long-term genetic and demographic studies (≥9 years) on mammals.
• Estimated contemporary N_e using single-sample methods: LDNE, Heterozygosity Excess, and Molecular Ancestry.
• Determined demographic abundance (N) via mark-recapture or catch-per-unit effort indices.

Main Results:

• Estimates of N_e varied widely within studies, indicating interpretation challenges.
• Correlations and trends between different N_e estimates, and between N_e and N, were inconsistent.
• In cases with consistent N_e-N trends, lower and more stable F_IS suggested appropriate spatial sampling scales.

Conclusions:

• The utility of N_e as a direct indicator of N is limited in some continuous mammal populations.
• F_IS stability may indicate suitable spatial scales for genetic monitoring in such populations.
• Further empirical research is needed to establish appropriate contexts for using N_e in monitoring programs for N or N_e trends.