The sheep of St Kilda

Clutton‐Brock, T. H.; Pemberton, J. M.; Coulson, Tim; Stevenson, Ian R.; MacColl, Andrew D. C.

doi:10.1017/cbo9780511550669.002

Cited by 30 publications

(65 citation statements)

References 532 publications

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“…Soay sheep are descended from the domesticated sheep present in NW Europe in the Bronze Age, and were taken to the St Kilda archipelago (57°49′N, 08°34′W, 65 km NW of the Outer Hebrides, Scotland) several thousand years ago (Clutton‐Brock, Pemberton, Coulson, Stevenson, & MacColl, ). A population has lived on the island of Soay (99 ha) since their arrival in St Kilda; meanwhile, the largest island in the archipelago, Hirta (638 ha), was home to a human population until 1930, when the people were evacuated along with their modern domesticated livestock.…”

Section: Methodsmentioning

confidence: 99%

“…The sheep population living in the Village Bay ( c . 170 ha) area of Hirta has been the subject of an intensive individual‐based study since 1985 (Clutton‐Brock et al, ). Females give birth in spring (March–May), and >95% of lambs born in Village Bay are captured within a week of birth, weighed, blood‐ and tissue‐sampled for genetic analysis and given a unique identifying ear tag.…”

Section: Methodsmentioning

confidence: 99%

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Reproductive effort influences intra‐seasonal variation in parasite‐specific antibody responses in wild Soay sheep

Hayward

Pilkington²,

Wilson

et al. 2019

Functional Ecology

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A trade‐off between reproduction and immune function has been suggested to potentially underpin between‐individual and genetic variation in reproductive strategy, immunity and life span, with potential consequences for host and parasite dynamics. Previous studies in wild animal populations have shown that experimentally induced or natural variation in reproductive effort is negatively associated with general immune markers. Few studies, however, have tackled this question by measuring specific immune responses against prevalent pathogens, and only rarely has variation in immune measures been linked to parasite burden, making it impossible to draw conclusions about the functional relevance of covariation between reproductive effort and immune markers. We collected faecal samples in a longitudinal manner from wild female Soay sheep across late pregnancy and early lactation and measured gastrointestinal nematode faecal egg count (FEC) and worm‐specific antibody responses. Faecal egg count was highly repeatable, with c. 80% of variation due to between‐individual differences, while three isotypes of worm‐specific and total antibodies had moderate repeatability (range: 11%–43%). Females making a greater reproductive effort (those that reproduced, and especially those with heavier litters) showed a more rapid increase in FEC across the season, while non‐reproducing females and those producing lighter litters experienced lower FEC and had higher antibody levels. Associations between antibodies and FEC were complex: worm‐specific immunoglobulin (Ig) G was negatively associated with FEC, while total IgM was positively associated, emphasizing the importance of measuring both immune markers and parasite burden in ecological studies. Our results support the predicted trade‐off between reproductive effort and parasite‐specific immunity: high reproductive effort can limit the ability of individuals to defend themselves against prevalent parasites, with potential downstream consequences for fitness and parasite transmission. A plain language summary is available for this article.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Reproductive effort influences intra‐seasonal variation in parasite‐specific antibody responses in wild Soay sheep

Hayward

Pilkington²,

Wilson

et al. 2019

Functional Ecology

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“…, 2006). Lambs are suckled until weaning around June and are independent by August (Clutton‐Brock et al. , 2004).…”

Section: Methodsmentioning

confidence: 99%

“…Across age and sex classes, there is substantial variation in the distributions of individual mortality rate, reproductive performance, body weight and parasite burden (Clutton‐Brock et al. , 1991, 1992, 2004; Craig et al.…”

Section: Methodsmentioning

confidence: 99%

Natural selection on a measure of parasite resistance varies across ages and environmental conditions in a wild mammal

Hayward

Wilson

Pilkington

et al. 2011

Journal of Evolutionary Biology

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Parasites detrimentally affect host fitness, leading to expectations of positive selection on host parasite resistance. However, as immunity is costly, host fitness may be maximized at low, but nonzero, parasite infection intensities. These hypotheses are rarely tested on natural variation in free‐living populations. We investigated selection on a measure of host parasite resistance in a naturally regulated Soay sheep population using a longitudinal data set and found negative correlations between parasite infection intensity and annual fitness in lambs, male yearlings and adult females. However, having accounted for confounding effects of body weight, the effect was only significant in lambs. Associations between fitness and parasite resistance were environment‐dependent, being strong during low‐mortality winters, but negligible during harsher high‐mortality winters. There was no evidence for stabilizing selection. Our findings reveal processes that may shape variation in parasite resistance in natural populations and illustrate the importance of accounting for correlated traits in selection analysis.

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“…The Soay sheep is a primitive breed that has been living on the island of Soay, in the St. Kilda archipelago, NW Scotland, for thousands of years in a largely unmanaged state. The population on Hirta has been unmanaged since its introduction from Soay in 1932 (Clutton-Brock et al 2004). Sheep resident in the Village Bay area of Hirta, comprising one-third of the Hirta population, have been the subject of intensive study since 1985 (Clutton-Brock et al 2004).…”

Section: Study Population Phenotypic Data and Samplingmentioning

confidence: 99%

Estimating quantitative genetic parameters in wild populations: a comparison of pedigree and genomic approaches

et al. 2014

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The estimation of quantitative genetic parameters in wild populations is generally limited by the accuracy and completeness of the available pedigree information. Using relatedness at genomewide markers can potentially remove this limitation and lead to less biased and more precise estimates. We estimated heritability, maternal genetic effects and genetic correlations for body size traits in an unmanaged long-term study population of Soay sheep on St Kilda using three increasingly complete and accurate estimates of relatedness: (i) Pedigree 1, using observation-derived maternal links and microsatellite-derived paternal links; (ii) Pedigree 2, using SNP-derived assignment of both maternity and paternity; and (iii) whole-genome relatedness at 37 037 autosomal SNPs. In initial analyses, heritability estimates were strikingly similar for all three methods, while standard errors were systematically lower in analyses based on Pedigree 2 and genomic relatedness. Genetic correlations were generally strong, differed little between the three estimates of relatedness and the standard errors declined only very slightly with improved relatedness information. When partitioning maternal effects into separate genetic and environmental components, maternal genetic effects found in juvenile traits increased substantially across the three relatedness estimates. Heritability declined compared to parallel models where only a maternal environment effect was fitted, suggesting that maternal genetic effects are confounded with direct genetic effects and that more accurate estimates of relatedness were better able to separate maternal genetic effects from direct genetic effects. We found that the heritability captured by SNP markers asymptoted at about half the SNPs available, suggesting that denser marker panels are not necessarily required for precise and unbiased heritability estimates. Finally, we present guidelines for the use of genomic relatedness in future quantitative genetics studies in natural populations.

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The sheep of St Kilda

Cited by 30 publications

References 532 publications

Reproductive effort influences intra‐seasonal variation in parasite‐specific antibody responses in wild Soay sheep

Reproductive effort influences intra‐seasonal variation in parasite‐specific antibody responses in wild Soay sheep

Natural selection on a measure of parasite resistance varies across ages and environmental conditions in a wild mammal

Estimating quantitative genetic parameters in wild populations: a comparison of pedigree and genomic approaches

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