Temporal Variability in Effective Size ( ) Identifies Potential Sources of Discrepancies Between Mark Recapture and...

Area of Science:

• Population genetics
• Ecology
• Conservation biology

Background:

• Estimating effective population size (Ne) and census size (N) is crucial for understanding wild populations.
• Few studies examine interannual variations in Ne and N, limiting our understanding of estimate repeatability and representativeness.

Purpose of the Study:

• To investigate the interannual variation in effective population size (Ne) and census size (N) in brook trout populations.
• To assess the representativeness of single-year estimates for long-term population dynamics.
• To compare mark-recapture and close-kin mark-recapture methods for estimating N.

Main Methods:

• Genotyping 5400 brook trout individuals across 7 populations over 5 years using 33 microsatellites.
• Estimating effective number of breeders (Nb) and effective population size (Ne) using genetic data.
• Estimating census size (N) via mark-recapture (electrofishing) and close-kin mark-recapture (CKMR).

Main Results:

• Annual Ne varied substantially (1.6- to 58-fold) within populations, with a median variation of 5-fold across all populations.
• Estimated Ne varied nearly twice as much as estimated N annually.
• Mark-recapture and CKMR estimates of N agreed for most populations, except where high Ne/N variation suggested insufficient sampling.

Conclusions:

• Single-year estimates of Ne are likely unrepresentative of long-term dynamics in small wild populations.
• At least 3-4 annual estimates are needed for a representative contemporary Ne.
• CKMR is a validated method for abundance estimation, and temporal Ne variation can explain discrepancies between N estimation methods.