CANCELLED - Heritability of maternal performance in wild grey seals

Background/Question/Methods

Individual variation provides the material upon which selection acts, and longitudinal studies spanning multiple generations with phenotypic records maintained for hundreds to thousands of individuals have proven invaluable in shedding light on such variation, contributing to our understanding of population dynamics. With archived tissue banks, we can now study the genetic basis of trait variation using high-throughput sequencing technologies, enabling identification of genome-wide genetic markers in virtually any species. Here, we used phenotypic records and genetic samples from a multi-decadal (1983-2020) study on a long-lived marine predator, the grey seal (Halichoerus grypus) on Sable Island, Nova Scotia, to perform quantitative genetic and genome-wide association analyses on eight maternal traits. We used restriction site associated DNA sequencing (ddRADseq) to genotype over 450 female grey seals for single nucleotide polymorphisms (SNPs) and from this data we estimated additive genetic variance and determined heritability for one morphological trait (maternal mass), six life-history traits (female length at first parturition, age at first parturition, parturition date, pup birth mass, PWM, lactation duration), and one behavioural trait (boldness) using animal models. We also performed genome-wide association analyses using SNP data to determine whether specific loci are associated with the measured traits.

Results/Conclusions

Using ddDNAseq, we obtained genotypic data for 476 female grey seals at 1,438 SNP loci. Post-quality filtering of genotypic and phenotypic data yielded a sample size of up to 460 females and 4727 repeated observations per trait. Heritability estimates adjusted for fixed effects estimated using an animal model were low to moderate for all traits (maternal mass = 0.13, body length at first parturition = 0.38, age at first parturition = 0.12, parturition date = 0.16, pup birth mass = 0.16, pup weaning mass = 0.16, lactation duration = 0.08, and boldness = 0.19). Low to moderate heritability and genetic variance estimates for traits that are closely related to fitness and condition are not unexpected, as selection may continually erode their genetic variance. We did not find any loci significantly associated with trait variation, suggesting the absence of genes of large effect on trait variation and polygenicity, which is also consistent with our understanding of the architecture of fitness-related traits. However, our results suggest that most traits linked to reproduction in grey seals exhibit some heritable genetic variation and therefore have the potential to evolve in response to selection imposed by changing environmental conditions and anthropogenic stressors.