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1.
Proc Biol Sci ; 289(1974): 20220330, 2022 05 11.
Article in English | MEDLINE | ID: mdl-35538786

ABSTRACT

Detecting microevolutionary responses to natural selection by observing temporal changes in individual breeding values is challenging. The collection of suitable datasets can take many years and disentangling the contributions of the environment and genetics to phenotypic change is not trivial. Furthermore, pedigree-based methods of obtaining individual breeding values have known biases. Here, we apply a genomic prediction approach to estimate breeding values of adult weight in a 35-year dataset of Soay sheep (Ovis aries). Comparisons are made with a traditional pedigree-based approach. During the study period, adult body weight decreased, but the underlying genetic component of body weight increased, at a rate that is unlikely to be attributable to genetic drift. Thus cryptic microevolution of greater adult body weight has probably occurred. Genomic and pedigree-based approaches gave largely consistent results. Thus, using genomic prediction to study microevolution in wild populations can remove the requirement for pedigree data, potentially opening up new study systems for similar research.


Subject(s)
Genome , Genomics , Animals , Body Weight , Genotype , Models, Genetic , Pedigree , Phenotype , Sheep
2.
Nat Commun ; 12(1): 2972, 2021 05 20.
Article in English | MEDLINE | ID: mdl-34016997

ABSTRACT

Inbreeding depression is ubiquitous, but we still know little about its genetic architecture and precise effects in wild populations. Here, we combine long-term life-history data with 417 K imputed SNP genotypes for 5952 wild Soay sheep to explore inbreeding depression on a key fitness component, annual survival. Inbreeding manifests in long runs of homozygosity (ROH), which make up nearly half of the genome in the most inbred individuals. The ROH landscape varies widely across the genome, with islands where up to 87% and deserts where only 4% of individuals have ROH. The fitness consequences of inbreeding are severe; a 10% increase in individual inbreeding FROH is associated with a 60% reduction in the odds of survival in lambs, though inbreeding depression decreases with age. Finally, a genome-wide association scan on ROH shows that many loci with small effects and five loci with larger effects contribute to inbreeding depression in survival.


Subject(s)
Animals, Wild/genetics , Inbreeding Depression , Inbreeding , Sheep/genetics , Animals , Female , Genetic Fitness , Genetic Loci , Genome , Genome-Wide Association Study , Homozygote , Male , Polymorphism, Single Nucleotide , Population Dynamics/statistics & numerical data , Scotland
3.
Proc Biol Sci ; 288(1945): 20202862, 2021 02 24.
Article in English | MEDLINE | ID: mdl-33622127

ABSTRACT

Sexual selection has been proposed as a force that could help maintain the diversity of major histocompatibility complex (MHC) genes in vertebrates. Potential selective mechanisms can be divided into pre-copulatory and post-copulatory, and in both cases, the evidence for occurrence is mixed, especially in natural populations. In this study, we used a large number of parent-offspring trios that were diplotyped for MHC class II genes in a wild population of Soay sheep (Ovis aries) to examine whether there was within-trio post-copulatory selection on MHC class II genes at both the haplotype and diplotype levels. We found there was transmission ratio distortion of one of the eight MHC class II haplotypes (E) which was transmitted less than expected by fathers, and transmission ratio distortion of another haplotype (A) which was transmitted more than expected by chance to male offspring. However, in both cases, these deviations were not significant after correction for multiple tests. In addition, we did not find any evidence of post-copulatory selection at the diplotype level. These results imply that, given known parents, there is no strong post-copulatory selection on MHC class II genes in this population.


Subject(s)
Histocompatibility Antigens Class II , Major Histocompatibility Complex , Alleles , Animals , Copulation , Genes, MHC Class II , Haplotypes , Histocompatibility Antigens Class II/genetics , Major Histocompatibility Complex/genetics , Male , Selection, Genetic , Sheep
4.
Science ; 365(6459): 1296-1298, 2019 09 20.
Article in English | MEDLINE | ID: mdl-31604239

ABSTRACT

Our understanding of the deterioration in immune function in old age-immunosenescence-derives principally from studies of modern human populations and laboratory animals. The generality and significance of this process for systems experiencing complex, natural infections and environmental challenges are unknown. Here, we show that late-life declines in an important immune marker of resistance to helminth parasites in wild Soay sheep predict overwinter mortality. We found senescence in circulating antibody levels against a highly prevalent nematode worm, which was associated with reduced adult survival probability, independent of changes in body weight. These findings establish a role for immunosenescence in the ecology and evolution of natural populations.


Subject(s)
Aging/immunology , Disease Resistance/immunology , Helminthiasis, Animal/immunology , Immunosenescence , Sheep/immunology , Sheep/parasitology , Animals , Antibodies, Helminth/blood , Body Weight , Female , Immunoglobulin G/blood , Linear Models , Male , Parasite Egg Count , Parasite Load , Scotland , Sheep Diseases/immunology , Sheep Diseases/parasitology , Survival Analysis
5.
BMC Evol Biol ; 18(1): 39, 2018 03 28.
Article in English | MEDLINE | ID: mdl-29592799

ABSTRACT

BACKGROUND: Understanding the genetic and environmental mechanisms governing variation in morphology or phenology in wild populations is currently an important challenge. While there is a general consensus that selection is stronger under stressful conditions, it remains unclear whether the evolutionary potential of traits should increase or decrease with increasingly stressful conditions. Here, we investigate how contrasting environmental conditions during growth may affect the maternal and genetic components of body mass in roe deer, the most abundant and widespread wild ungulate in Western Europe. Body mass is a key life history trait that strongly influences both survival and reproductive performance in large herbivores. We used pedigrees and animal models to determine the variance components of juvenile and adult winter body mass in two populations experiencing contrasting early-life conditions. RESULTS: Our analyses showed that roe deer at Chizé, where habitat was poor and unpredictable, exhibited very low genetic variance in juvenile body mass. Instead, variance in mass was mainly driven by among-cohort differences in early-life conditions and maternal environment. In contrast, roe deer at Bogesund, where resource availability during the critical period of fawn rearing was higher, displayed a substantial level of genetic variance in body mass. We discuss the potential role of past demography and viability selection on fawn body mass on the erosion of genetic variance in the poor habitat. CONCLUSIONS: Our study highlights the importance of accounting for both spatial (i.e. between-population variation) and temporal (i.e. cohort variation) heterogeneity in environmental conditions, especially in early life, to understand the potential for adaptive responses of wild populations to selection.


Subject(s)
Body Weight/genetics , Deer/anatomy & histology , Deer/genetics , Genetics, Population , Animals , Demography , Ecosystem , Europe , Female , Genetic Variation , Male , Reproduction/physiology , Seasons
6.
Sci Rep ; 7(1): 9991, 2017 08 30.
Article in English | MEDLINE | ID: mdl-28855677

ABSTRACT

In humans, the effect of paternal age at conception (PAC) on offspring leukocyte telomere length (LTL) is well established, with older fathers thought to pass on longer telomeres to their offspring in their sperm. Few studies have looked for PAC effects in other species, but it has been hypothesised that the effect will be exacerbated in polygamous species with higher levels of sperm competition and production. We test for maternal (MAC) and paternal age at conception effects on offspring LTL in Soay sheep, a primitive breed experiencing strong sperm competition. We use qPCR to measure relative telomere length in 389 blood samples (n = 318 individuals) collected from an unmanaged population of sheep on St Kilda, where individual age and parentage are known. We find no evidence that either MAC or PAC are associated with LTL in offspring across the age range, or when considering only young lambs (n = 164). This is the first study to test for parental age effects on offspring LTL in a wild mammal population, and the results contrast with the findings of numerous human studies that find a PAC effect, as well as predictions of a stronger PAC effect in polygamous species.


Subject(s)
Fertilization , Leukocytes/cytology , Parents , Telomere Homeostasis , Animals , Female , Male , Real-Time Polymerase Chain Reaction , Sheep
7.
Naturwissenschaften ; 104(7-8): 68, 2017 Aug.
Article in English | MEDLINE | ID: mdl-28761976

ABSTRACT

Nutrient availability is predicted to interact with herbivore population densities. Competition for low quality food at high density may reduce summer food intake, and in turn winter survival. Conversely, low population density may favor physiological recovery through better access to better quality spring forage. Here, we take advantage of the long-term study of the Soay sheep population of St. Kilda (Scotland) to measure plasma protein markers and immunity in two consecutive summers with contrasting population densities. We show that, following a winter die-off resulting in a shift to low population density, albumin and total proteins increased, but only in adult sheep. The effect was not solely attributable to selective disappearance of malnourished sheep. Similarly, the concentration of antibodies was higher following the die-off, potentially indicating recovery of immune function. Overall, our results are consistent with the physiological recovery of surviving individuals after a harsh winter.


Subject(s)
Herbivory , Animals , Population Density , Scotland , Seasons , Sheep
8.
Heredity (Edinb) ; 118(1): 64-77, 2017 01.
Article in English | MEDLINE | ID: mdl-27876804

ABSTRACT

Experimental studies often find that inbreeding depression is more severe in harsh environments, but the few studies of in situ wild populations available to date rarely find strong support for this effect. We investigated evidence for inbreeding depression by environment interactions in nine traits in the individually monitored Soay sheep population of St Kilda, using genomic inbreeding coefficients based on 37 037 single-nucleotide polymorphism loci, and population density as an axis of environmental variation. All traits showed variation with population density and all traits showed some evidence for depression because of either an individual's own inbreeding or maternal inbreeding. However, only six traits showed evidence for an interaction in the expected direction, and only two interactions were statistically significant. We identify three possible reasons why wild population studies may generally fail to find strong support for interactions between inbreeding depression and environmental variation compared with experimental studies. First, for species with biparental inbreeding only, the amount of observed inbreeding in natural populations is generally low compared with that used in experimental studies. Second, it is possible that experimental studies sometimes actually impose higher levels of stress than organisms experience in the wild. Third, some purging of the deleterious recessive alleles that underpin interaction effects may occur in the wild.


Subject(s)
Genetics, Population , Inbreeding Depression , Sheep/genetics , Animals , Body Size , Environment , Female , Genetic Fitness , Genotype , Male , Models, Genetic , Population Density , Scotland
9.
J Evol Biol ; 30(1): 96-111, 2017 Jan.
Article in English | MEDLINE | ID: mdl-27747954

ABSTRACT

When estimating heritability in free-living populations, it is common practice to account for common environment effects, because of their potential to generate phenotypic covariance among relatives thereby biasing heritability estimates. In quantitative genetic studies of natural populations, however, philopatry, which results in relatives being clustered in space, is rarely accounted for. The two studies that have been carried out so far suggest absolute declines in heritability estimates of up to 43% when accounting for space sharing by relatives. However, due to methodological limitations these estimates may not be representative. We used data from the St. Kilda Soay sheep population to estimate heritabilities with and without accounting for space sharing for five traits for which there is evidence for additive genetic variance (birthweight, birth date, lamb August weight, and female post-mortem jaw and metacarpal length). We accounted for space sharing by related females by separately incorporating spatial autocorrelation, and a home range similarity matrix. Although these terms accounted for up to 18% of the variance in these traits, heritability estimates were only reduced by up to 7%. Our results suggest that the bias caused by not accounting for space sharing may be lower than previously thought. This suggests that philopatry does not inevitably lead to a large bias if space sharing by relatives is not accounted for. We hope our work stimulates researchers to model shared space when relatives in their study population share space, as doing so will enable us to better understand when bias may be of particular concern.


Subject(s)
Genetic Variation , Phenotype , Sheep/genetics , Animals , Birth Weight , Body Weight , Female , Inheritance Patterns , Sheep/anatomy & histology , Sheep, Domestic
10.
Epidemiol Infect ; 144(9): 1879-88, 2016 07.
Article in English | MEDLINE | ID: mdl-26829883

ABSTRACT

We assessed evidence of exposure to viruses and bacteria in an unmanaged and long-isolated population of Soay sheep (Ovis aries) inhabiting Hirta, in the St Kilda archipelago, 65 km west of Benbecula in the Outer Hebrides of Scotland. The sheep harbour many metazoan and protozoan parasites but their exposure to viral and bacterial pathogens is unknown. We tested for herpes viral DNA in leucocytes and found that 21 of 42 tested sheep were infected with ovine herpesvirus 2 (OHV-2). We also tested 750 plasma samples collected between 1997 and 2010 for evidence of exposure to seven other viral and bacterial agents common in domestic Scottish sheep. We found evidence of exposure to Leptospira spp., with overall seroprevalence of 6·5%. However, serological evidence indicated that the population had not been exposed to border disease, parainfluenza, maedi-visna, or orf viruses, nor to Chlamydia abortus. Some sheep tested positive for antibodies against Mycobacterium avium subsp. paratuberculosis (MAP) but, in the absence of retrospective faecal samples, the presence of this infection could not be confirmed. The roles of importation, the pathogen-host interaction, nematode co-infection and local transmission warrant future investigation, to elucidate the transmission ecology and fitness effects of the few viral and bacterial pathogens on Hirta.


Subject(s)
Bacteria/classification , Bacteria/isolation & purification , Bacterial Infections/veterinary , Virus Diseases/veterinary , Viruses/classification , Viruses/isolation & purification , Animals , Bacterial Infections/epidemiology , Bacterial Infections/microbiology , Female , Hebrides/epidemiology , Male , Seroepidemiologic Studies , Sheep, Domestic , Virus Diseases/epidemiology , Virus Diseases/virology
11.
Mol Ecol ; 22(3): 757-73, 2013 Feb.
Article in English | MEDLINE | ID: mdl-22998224

ABSTRACT

Identifying the genes underlying phenotypic variation in natural populations can provide novel insight into the evolutionary process. The candidate gene approach has been applied to studies of a number of traits in various species, in an attempt to elucidate their genetic basis. Here, we test the application of the candidate gene approach to identify the loci involved in variation in gastrointestinal parasite burden, a complex trait likely to be controlled by many loci, in a wild population of Soay sheep. A comprehensive literature review, Gene Ontology databases, and comparative genomics resources between cattle and sheep were used to generate a list of candidate genes. In a pilot study, these candidates, along with 50 random genes, were then sequenced in two pools of Soay sheep; one with low gastrointestinal nematode burden and the other high, using a NimbleGen sequence capture experiment. Further candidates were identified from single nucleotide polymorphisms (SNPs) that were highly differentiated between high- and low-resistance sheep breeds. A panel of 192 candidate and control SNPs were then typed in 960 individual Soay sheep to examine whether they individually explained variation in parasite burden, as measured as faecal egg count, as well as two immune measures (Teladorsagia circumcincta-specific antibodies and antinuclear antibodies). The cumulative effect of the candidate and control SNPs were estimated by fitting genetic relationship matrices (GRMs) as random effects in animal models of the three traits. No more significant SNPs were identified in the pilot sequencing experiment and association study than expected by chance. Furthermore, no significant difference was found between the proportions of candidate or control SNPs that were found to be significantly associated with parasite burden/immune measures. No significant effect of the candidate or control gene GRMs was found. There is thus little support for the candidate gene approach to the identification of loci explaining variation in parasitological and immunological traits in this population. However, a number of SNPs explained significant variation in multiple traits and significant correlations were found between the proportions of variance explained by individual SNPs across multiple traits. The significant SNPs identified in this study may still, therefore, merit further investigation.


Subject(s)
Parasite Load , Sheep/genetics , Sheep/immunology , Sheep/parasitology , Trichostrongyloidiasis/veterinary , Animals , Antibodies, Antinuclear/blood , Antibodies, Helminth/blood , Genetic Association Studies , Oligonucleotide Array Sequence Analysis , Parasite Egg Count , Pilot Projects , Polymorphism, Single Nucleotide , Quantitative Trait Loci , Sequence Analysis, DNA , Sheep Diseases/genetics , Sheep Diseases/immunology , Sheep Diseases/parasitology , Trichostrongyloidea , Trichostrongyloidiasis/genetics , Trichostrongyloidiasis/immunology
12.
J Evol Biol ; 25(12): 2457-69, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23039875

ABSTRACT

The interaction between philopatry and nonrandom mating has important consequences for the genetic structure of populations, influencing co-ancestry within social groups but also inbreeding. Here, using genetic paternity data, we describe mating patterns in a wild population of red deer (Cervus elaphus) which are associated with marked consequences for co-ancestry and inbreeding in the population. Around a fifth of females mate with a male with whom they have mated previously, and further, females frequently mate with a male with whom a female relative has also mated (intralineage polygyny). Both of these phenomena occur more than expected under random mating. Using simulations, we demonstrate that temporal and spatial factors, as well as skew in male breeding success, are important in promoting both re-mating behaviours and intralineage polygyny. However, the information modelled was not sufficient to explain the extent to which these behaviours occurred. We show that re-mating and intralineage polygyny are associated with increased pairwise relatedness in the population and a rise in average inbreeding coefficients. In particular, the latter resulted from a correlation between male relatedness and rutting location, with related males being more likely to rut in proximity to one another. These patterns, alongside their consequences for the genetic structure of the population, have rarely been documented in wild polygynous mammals, yet they have important implications for our understanding of genetic structure, inbreeding avoidance and dispersal in such systems.


Subject(s)
Deer/physiology , Inbreeding/statistics & numerical data , Sexual Behavior, Animal , Animals , Deer/genetics , Female , Male , Pedigree
13.
Mol Ecol ; 21(12): 2977-90, 2012 Jun.
Article in English | MEDLINE | ID: mdl-22432567

ABSTRACT

Understanding the maintenance of genetic variation in natural populations is a core aim of evolutionary genetics. Insight can be gained by quantifying selection at the level of the genotype, as opposed to the phenotype. Here, we show that in a natural population of Soay sheep which is polymorphic for coat pattern, recessive genetic variants at the causal gene, agouti signalling protein (ASIP) are associated with reduced lifetime fitness. This was due primarily to a reduction in juvenile survival of uniformly coloured (self-type) sheep, which are homozygous recessive, and occurs despite significantly higher reproductive success in surviving self-type adults. Consistent with their relatively low fitness, we show that the frequency of self-type individuals has declined from 1985 to 2008. Remarkably though, the frequency of the underlying self-allele has increased, because the frequency of heterozygous individuals (who harbour the majority of all self-alleles) has increased. Indeed, the ratio of observed/expected heterozygous individuals has increased during the study, such that there is now a significant excess of heterozygotyes. By employing gene-dropping simulations, we show that microevolutionary trends in the frequency and excess of ASIP heterozygotes are too pronounced to be caused by genetic drift. Studying this polymorphism at the level of phenotype rather than underlying genotype would have failed to detect cryptic fitness differences. We would also have been unable to rule out genetic drift as an evolutionary force driving genetic change. This highlights the importance of resolving the underlying genetic basis of phenotypic variation in explaining evolutionary dynamics.


Subject(s)
Agouti Signaling Protein/genetics , Biological Evolution , Hair Color/genetics , Selection, Genetic , Sheep/genetics , Wool , Animals , Genetic Drift , Genetic Variation , Genotype , Heterozygote , Models, Genetic , Phenotype , Polymorphism, Genetic , Sheep/anatomy & histology , Sheep/physiology
14.
Ecol Lett ; 14(10): 985-92, 2011 Oct.
Article in English | MEDLINE | ID: mdl-21790931

ABSTRACT

Accurate prediction of life history phenomena and characterisation of selection in free-living animal populations are fundamental goals in evolutionary ecology. In density regulated, structured populations, where individual state influences fate, simple and widely used approaches based on individual lifetime measures of fitness are difficult to justify. We combine recently developed structured population modelling tools with ideas from modern evolutionary game theory (adaptive dynamics) to understand selection on allocation of female reproductive effort to singletons or twins in a size-structured population of feral sheep. In marked contrast to the classical selection analyses, our model-based approach predicts that the female allocation strategy is under negligible directional selection. These differences arise because classical selection analysis ignores components of offspring fitness and fails to consider selection over the complete life cycle.


Subject(s)
Models, Biological , Reproduction/physiology , Sheep/physiology , Animals , Biological Evolution , Quantitative Trait, Heritable , Reproduction/genetics , Selection, Genetic , Sheep/genetics
15.
J Evol Biol ; 24(8): 1664-76, 2011 Aug.
Article in English | MEDLINE | ID: mdl-21658142

ABSTRACT

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.


Subject(s)
Selection, Genetic , Sheep Diseases/parasitology , Trichostrongylosis/veterinary , Age Factors , Animals , Body Size , Feces/parasitology , Female , Genotype , Immunity, Innate , Male , Phenotype , Reproduction , Sex Factors , Sheep Diseases/genetics , Sheep Diseases/immunology , Sheep, Domestic , Trichostrongylosis/immunology , Trichostrongylosis/parasitology
16.
Mol Ecol ; 20(5): 910-9, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21324010

ABSTRACT

Digital gene expression (DGE) analysis offers a route to gene discovery which by-passes the need to develop bespoke arrays for nonmodel species, and is therefore a potentially valuable tool for molecular ecologists. Scottish blackface sheep, which vary in resistance to the common abomasal parasitic nematode Teladorsagia circumcincta, were trickle-infected with L3 larvae over 3 months to mimic the natural progression of infection. DGE was performed on abomasal lymph node tissue after the resolution of infection in resistant animals. Susceptible (low resistance) animals showed a large number of differentially expressed genes associated with inflammation and cell activation, but generally few differentially regulated genes in either the susceptible or the resistant group were directly involved in the adaptive immune function. Our results are consistent with the hypothesis that both resistance and susceptibility are active responses to infection and that susceptibility is associated with dysfunction in T cell differentiation and regulation.


Subject(s)
Sheep Diseases/genetics , Sheep, Domestic/genetics , Sheep, Domestic/parasitology , Trichostrongyloidea/physiology , Trichostrongyloidiasis/veterinary , Animals , Female , Gastrointestinal Tract/immunology , Gastrointestinal Tract/parasitology , Gene Expression Profiling , Immunity, Innate/genetics , Sheep , Sheep Diseases/immunology , Sheep Diseases/parasitology , Sheep, Domestic/immunology , Trichostrongyloidiasis/genetics , Trichostrongyloidiasis/immunology
17.
J Evol Biol ; 24(4): 772-83, 2011 Apr.
Article in English | MEDLINE | ID: mdl-21288272

ABSTRACT

By determining access to limited resources, social dominance is often an important determinant of fitness. Thus, if heritable, standard theory predicts mean dominance should evolve. However, dominance is usually inferred from the tendency to win contests, and given one winner and one loser in any dyadic contest, the mean proportion won will always equal 0.5. Here, we argue that the apparent conflict between quantitative genetic theory and common sense is resolved by recognition of indirect genetic effects (IGEs). We estimate selection on, and genetic (co)variance structures for, social dominance, in a wild population of red deer Cervus elaphus, on the Scottish island of Rum. While dominance is heritable and positively correlated with lifetime fitness, contest outcomes depend as much on the genes carried by an opponent as on the genotype of a focal individual. We show how this dependency imposes an absolute evolutionary constraint on the phenotypic mean, thus reconciling theoretical predictions with common sense. More generally, we argue that IGEs likely provide a widespread but poorly recognized source of evolutionary constraint for traits influenced by competition.


Subject(s)
Biological Evolution , Deer/physiology , Social Dominance , Animals , Deer/genetics
18.
Genet Res (Camb) ; 92(4): 273-81, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20943008

ABSTRACT

Historical information can be used, in addition to pedigree, traits and genotypes, to map quantitative trait locus (QTL) in general populations via maximum likelihood estimation of variance components. This analysis is known as linkage disequilibrium (LD) and linkage mapping, because it exploits both linkage in families and LD at the population level. The search for QTL in the wild population of Soay sheep on St. Kilda is a proof of principle. We analysed the data from a previous study and confirmed some of the QTLs reported. The most striking result was the confirmation of a QTL affecting birth weight that had been reported using association tests but not when using linkage-based analyses.


Subject(s)
Chromosome Mapping/methods , Linkage Disequilibrium , Models, Statistical , Quantitative Trait Loci , Alleles , Animals , Genetic Markers , Microsatellite Repeats/genetics , Phenotype , Sheep
19.
Mol Ecol ; 19(15): 3101-13, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20629954

ABSTRACT

For mammals with a polygynous mating system, dispersal is expected to be male-biased. However, with the increase in empirical studies, discrepancies are arising between the expected and observed direction/extent of the bias in dispersal. In this study, we assessed sex-biased dispersal in red deer (Cervus elaphus) on 13 estates from the Scottish Highlands. A total of 568 adult individuals were genotyped at 21 microsatellite markers and sequenced for 821 bp of the mitochondrial control region. Estimates of population structure with mitochondrial sequences were eight times larger than that obtained with microsatellite data (F(st'-mtDNA) = 0.831; F(st'-micros) = 0.096) indicating overall male-biased dispersal in the study area. Comparisons of microsatellite data between the sexes indicated a predominance of male-biased dispersal in the study area but values of F(ST) and relatedness were only slighter larger for females. Individual-based spatial autocorrelation analysis generated a similar pattern of relatedness across geographical distances for both sexes, with differences only significant at two distance intervals (25-30 and 70-112 km). Patterns of relatedness differed between estates, male biased-dispersal was detected in eight estates but no sex-biased dispersal was found in the remaining five. Neither population density nor landscape cover was found to be associated with the patterns of relatedness found across the estates. Differences in management strategies that could influence age structure, sex ratio and dispersal behaviour are proposed as potential factors influencing the relatedness patterns observed. This study provides new insights on dispersal of a strongly polygynous mammal at geographical scales relevant for management and conservation.


Subject(s)
Deer/genetics , Genetics, Population , Sexual Behavior, Animal , Animals , DNA, Mitochondrial/genetics , Environment , Female , Genotype , Geography , Male , Microsatellite Repeats , Population Density , Scotland , Sequence Analysis, DNA
20.
Parasitology ; 137(12): 1799-804, 2010 Oct.
Article in English | MEDLINE | ID: mdl-20546642

ABSTRACT

SUMMARYThe sheep ked has been largely eradicated in the UK but persists in the feral Soay sheep of St Kilda in the Outer Hebrides. Sheep keds transmit Trypanosoma melophagium, but parasitaemias are typically cryptic and this trypanosome has not been recorded in the St Kilda sheep. Trypanosomes were detected by PCR in preserved keds and were also found in gut smears from live keds; one infected gut was used to establish the trypanosome in vitro. Examination of the morphology of bloodstream forms from culture confirmed its identity as T. melophagium. Most keds were found to harbour the trypanosome, particularly those collected from lambs. DNA was extracted from preserved keds and from trypanosomes grown in vitro. Sequence analysis of the small subunit ribosomal RNA (SSU rRNA) gene and the spliced leader transcript showed the T. melophagium sequences to be very similar to those from T. theileri. A partial sequence of the ked SSU rRNA gene was also obtained. The close genetic relationship of T. melophagium and T. theileri suggests that T. melophagium represents a lineage of T. theileri that adapted to transmission by sheep keds and hence became a specific parasite of sheep.


Subject(s)
Diptera/parasitology , Insect Vectors/parasitology , Sheep Diseases/transmission , Trypanosoma/classification , Trypanosoma/isolation & purification , Trypanosomiasis/transmission , Animals , Base Sequence , DNA, Protozoan/analysis , DNA, Protozoan/genetics , DNA, Protozoan/isolation & purification , Ectoparasitic Infestations/parasitology , Ectoparasitic Infestations/veterinary , Molecular Sequence Data , Prevalence , Scotland , Sequence Analysis, DNA , Sheep , Sheep Diseases/parasitology , Trypanosoma/genetics , Trypanosomiasis/parasitology , Trypanosomiasis/veterinary
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