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. 2023 Jul 14;16(8):1472-1482.
doi: 10.1111/eva.13580. eCollection 2023 Aug.

Alternative life-history strategy contributions to effective population size in a naturally spawning salmon population

Erika King  1 , Megan V McPhee  1 , Scott C Vulstek  2 , Curry J Cunningham  1 , Joshua R Russell  2 , David A Tallmon  1   3
Affiliations

Alternative life-history strategy contributions to effective population size in a naturally spawning salmon population

Erika King et al. Evol Appl. .

Abstract

Alternative life-history tactics are predicted to affect within-population genetic processes but have received little attention. For example, the impact of precocious males on effective population size (N e) has not been quantified directly in Pacific salmon Oncorhynchus spp., even though they can make up a large percentage of the total male spawners. We investigated the contribution of precocial males ("jacks") to N e in a naturally spawning population of Coho Salmon O. kisutch from the Auke Creek watershed in Juneau, Alaska. Mature adults that returned from 2009 to 2019 (~8000 individuals) were genotyped at 259 single-nucleotide polymorphism (SNP) loci for parentage analysis. We used demographic and genetic methods to estimate the effective number of breeders per year (N b). Jack contribution to N b was assessed by comparing values of N b calculated with and without jacks and their offspring. Over a range of N b values (108-406), the average jack contribution to N b from 2009 to 2015 was 12.9% (SE = 3.8%). Jacks consistently made up over 20% of the total male spawners. The presence of jacks did not seem to influence N b/N. The linkage disequilibrium N e estimate was lower than the demographic estimate, possibly due to immigration effects on population genetic processes: based on external marks and parentage data, we estimated that immigrant spawners produced 4.5% of all returning offspring. Our results demonstrate that jacks can influence N b and N e and can make a substantial contribution to population dynamics and conservation of threatened stocks.

Keywords: SNPs; effective number of breeders; effective population size; life history; salmonids.

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Conflict of interest statement

We declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Auke Creek Coho Salmon population size including unknown sex/type adult individuals (N) and effective population size (N eD) for four overlapping generations calculated using yearly effective number of breeders values and the proportional contribution of offspring from each year.
FIGURE 2
FIGURE 2
Inbreeding effective number of breeders over time using the demographic method (N bD), linkage disequilibrium method (N bLD), and SALMONNb method (N bS) for Auke Creek Coho Salmon from 2009 to 2015. 95% CIs are included (for N bLD and N bS).
See this image and copyright information in PMC

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