Browsing by Subject "inbreeding"

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  • Hämäläinen, Aurora (Helsingin yliopisto, 2020)
    The traditional method of estimating inbreeding is based on pedigree information, which only considers the known common ancestors of the animals. In recent years, the animal breeding sector has introduced new genomic tools in breeding schemes. The aim of this study was to estimate and compare the level of inbreeding in Finnish Yorkshire and Finnish Landrace pigs using pedigree and genomic methods. Data consisted of pedigree and genotype information from both breeds. In pedigree data there were 503 315 Landrace and 549 296 Yorkshire animals after pruning for pedigree completeness and errors in the data. In the genotype data, there were 522 individuals of Landrace and 934 individuals of Yorkshire animals after pruning. Inbreeding coefficients (FPED) were estimated from pedigree data using RelaX2 program and for genomic data using PLINK by detecting runs of homozygosity (FROH). Percentage of homozygosity (FPH) was also studied from genomic data. Yearly rate of inbreeding based on pedigree raised steadily. Average inbreeding coefficients from year 2014 were 0.10 for Landrace and 0.15 for Yorkshire. The average inbreeding coefficient based on ROHs for animals born in year 2014 were 0.21 for Landrace and 0.25 for Yorkshire animals. Correlation between pedigree-based estimate and genomic-based FROH was found to be quite low for both breeds; 0.51 for Landrace and 0.58 for Yorkshire. The correlation between the two genomic based methods FROH and FPH was high, 0.86 for Landrace and 0.89 for Yorkshire. The level of inbreeding was found to be quite high in both breeds. The genomic-based estimates were higher overall than pedigree-based estimates, which indicates that pedigree data are missing some common ancestors. Based on the results, the level of inbreeding in Finnish pig breeds should be monitored to maintain sufficient genetic diversity in the populations.
  • Martikainen, K.; Tyrisevä, A. M.; Matilainen, K.; Pösö, J.; Uimari, P. (2017)
    Single nucleotide polymorphism (SNP) data enable the estimation of inbreeding at the genome level. In this study, we estimated inbreeding levels for 19,075 Finnish Ayrshire cows genotyped with a low-density SNP panel (8K). The genotypes were imputed to 50K density, and after quality control, 39,144 SNPs remained for the analysis. Inbreeding coefficients were estimated for each animal based on the percentage of homozygous SNPs (F-PH), runs of homozygosity (F-ROH) and pedigree (F-PED). Phenotypic records were available for 13,712 animals including non-return rate (NRR), number of inseminations (AIS) and interval from first to last insemination (IFL) for heifers and up to three parities for cows, as well as interval from calving to first insemination (ICF) for cows. Average F-PED was 0.02, F-ROH 0.06 and F-PH 0.63. A correlation of 0.71 was found between F-PED and F-ROH, 0.66 between F-PED and F-PH and 0.94 between F-ROH and F-PH. Pedigree-based inbreeding coefficients did not show inbreeding depression in any of the traits. However, when F-ROH or F-PH was used as a covariate, significant inbreeding depression was observed; a 10% increase in F-ROH was associated with 5days longer IFL0 and IFL1, 2weeks longer IFL3 and 3days longer ICF2 compared to non-inbred cows.
  • Martikainen, K.; Sironen, A.; Uimari, P. (2018)
    Inbreeding increases homozygosity, which in turn increases the frequency of harmful recessive alleles, resulting in inbreeding depression. Inbreeding depression on fertility reduces the profitability of dairy farming by decreasing the lifetime milk production of cows and by increasing insemination and veterinary costs. Continuous homozygous segments, called runs of homozygosity (ROH), are currently considered to provide an effective measure of genomic inbreeding. The aim of this study was to estimate the effect of increased intrachromosomal homozygosity for female fertility in the Finnish Ayrshire population using ROH and haplotype analysis. Genotypes were obtained from 13,712 females with the Illumina BovineLD v.2 BeadChip low-density panel (Illumina Inc., San Diego, CA) and imputed to 50K density. After quality control, 40,554 single nucleotide polymorphisms remained for the analysis. Phenotypic data consisted of records for nonreturn rate, intervals from first to last insemination (IFL), and intervals from calving to first insemination. The raw phenotypic values were preadjusted for systematic effects before statistical analyses. The ROH-based inbreeding coefficients (F-ROH) were used as covariats in the mixed model equation to estimate the association between inbreeding and inbreeding depression on female fertility. First, we estimated the effect of increased chromosomal F-ROH. We detected significant inbreeding depression on IFL. Based on our results, a 10% increase in F-ROH on chromosomes 2, 18, and 22 were associated with IFL of heifers lengthening by 1.6, 0.9, and 0.7 d, respectively. Similarly, a 10% increase in F-ROH on chromosome 15 was associated with IFL of second-parity cows increasing by 2.3 d. Next, we located the regions within the chromosomes showing inbreeding depression. Our analysis revealed regions near the beginning of chromosome 2 and toward the ends of chromosomes 15, 18, and 22 that were associated with inbreeding depression on IFL. Last, we performed a haplotype analysis for the detected regions. The most promising haplotypes of each region were associated with IFL of heifers increasing by 4.4, 3.2, and 4.1 d on chromosomes 2, 18, and 22, respectively. The haplotype on chromosome 15 associated with IFL of second-parity cows increasing by 7.6 d. Overall, the breeding program requires inbreeding control, as increased genomic inbreeding in our study was associated with reduced reproductive ability in Finnish Ayrshire cattle.
  • Hakala, Sanja Maria; Seppä, Perttu; Helanterä, Heikki (2019)
    The extreme diversity of dispersal strategies in ants is unique among terrestrial animals. The nature of ant colonies as social, perennial, and sessile superorganisms is the basis for understanding this diversity, together with the inclusive-fitness framework for social evolution. We review ant dispersal strategies, with the aim of identifying future research directions on ant dispersal and its evolution. We list ultimate and proximate determinants of dispersal traits and the ecological and evolutionary consequences of dispersal for population structures and dynamics, as well as species communities. We outline the eco-evolutionary feedbacks between the multitude of traits affecting dispersal evolution and the likely evolutionary routes and ecological drivers in transitions among the diverse ant dispersal strategies. We conclude by presenting a research framework to fill the gaps in current knowledge, including comparative studies of colony life histories and population structures and theoretical models of the eco-evolutionary dynamics affecting dispersal, in an inclusive-fitness framework.
  • Paakala, Elina (Helsingfors universitet, 2011)
    The aim of this master’s thesis was to study genetic diversity within and between ten dog breeds. The original data was produced by Finnzymes Oy and it contained raw data files that were used to genotype microsatellite markers. The final data contained information from 395 dogs belonging to ten fairly different dog breeds. The amount of dogs per breed was from 31 to 53. The data was genotyped with 18 microsatellite markers. A llelic richness varied between 2,0 – 9,9. The most variable microsatellite locus was AHT137 and the least variable AHTk211. Over all loci allelic richness was highest in Jack Russell Terrier and lowest in Cavalier King Charles Spaniel. S c hipperke had the largest amount of microsatellite loci that were not in Hardy- Weinberg equilibrium. In Coton de Tulear, German Shepherd Dog and Finnish Lapphund all microsatellite loci were in Hardy-Weinberg equilibrium. The lowest overall heterozygosity was in Cavalier King Charles Spaniel (0,50) and highest in Finnish Lapphund (0,73). The only statistically significant FIS-values were in Schipperke in locus INU030 (0,39) and over all loci (0,11). The most distant breeds according to FST-value were Cavalier King Charles Spaniel and Rough Collie (0,34) and the closest breeds were Chihuahua and Coton de Tulear (0,07). Overall between breeds diversity was 17,7 %. On the grounds of these results the ten breeds are distinct populations. Coton de Tulear had clearly the highest amount of allele pairs in linkage disequilibrium (94) and Tibetan Spaniel the lowest amount (15). Effective population size was lowest in Rough Collie (35) and highest in Chihuahua (86). Based on many population genetic measures Cavalier King Charles Spaniel, Rough Collie and Schipperke seem to have the lowest genetic diversity and Chihuahua, Jack Russel Terrier and Finnish Lapphound the highest. Reasons for different levels of genetic diversity can be found on histories of these dog breeds.
  • Sarhan, Alia; Kokko, Hanna (2007)
    Many hypotheses have been proposed to explain multiple mating in females. One of them is bet hedging, that is avoiding having no or very few offspring in any given generation, rather than maximizing the expected number of offspring. However, within-generation bet hedging is generally believed to be an unimportant evolutionary force, except in very small populations. In this study, we derive predictions of the bet-hedging hypothesis for a case in which local insect populations are often small, offspring performance varies, for example, due to inbreeding depression, and the groups of gregarious larvae have to exceed a threshold size before they are likely to survive throughout the larval stage. These conditions exist for populations of the Glanville fritillary butterfly (Melitaea cinxia), potentially making bet-hedging benefits larger than usual. We observed matings in a field cage, which allowed detailed observations under practically natural conditions, and analyzed genetic paternity of egg clutches laid by females under direct observation. The egg-laying and survival patterns are in line with the predictions, supporting the hypothesis that multiple mating in M. cinxia presents a rare case of within-generation bet hedging.
  • Fountain, Toby; Butlin, Roger K.; Reinhardt, Klaus; Otti, Oliver (2015)
    In some species, populations with few founding individuals can be resilient to extreme inbreeding. Inbreeding seems to be the norm in the common bed bug, Cimex lectularius, a flightless insect that, nevertheless, can reach large deme sizes and persist successfully. However, bed bugs can also be dispersed passively by humans, exposing inbred populations to gene flow from genetically distant populations. The introduction of genetic variation through this outbreeding could lead to increased fitness (heterosis) or be costly by causing a loss of local adaptation or exposing genetic incompatibility between populations (outbreeding depression). Here, we addressed how inbreeding within demes and outbreeding between distant populations impact fitness over two generations in this re-emerging public health pest. We compared fitness traits of families that were inbred (mimicking reproduction following a founder event) or outbred (mimicking reproduction following a gene flow event). We found that outbreeding led to increased starvation resistance compared to inbred families, but this benefit was lost after two generations of outbreeding. No other fitness benefits of outbreeding were observed in either generation, including no differences in fecundity between the two treatments. Resilience to inbreeding is likely to result from the history of small founder events in the bed bug. Outbreeding benefits may only be detectable under stress and when heterozygosity is maximized without disruption of coadaptation. We discuss the consequences of these results both in terms of inbreeding and outbreeding in populations with genetic and spatial structuring, as well as for the recent resurgence of bed bug populations.
  • Bos, Nick; Pulliainen, Unni; Sundström, Liselotte; Freitak, Dalial (2016)
    Starvation is one of the most common and severe stressors in nature. Not only does it lead to death if not alleviated, it also forces the starved individual to allocate resources only to the most essential processes. This creates energetic trade-offs which can lead to many secondary challenges for the individual. These energetic trade-offs could be exacerbated in inbred individuals, which have been suggested to have a less efficient metabolism. Here, we studied the effect of inbreeding on starvation resistance in a natural population of Formica exsecta ants, with a focus on survival and tissue-specific expression of stress, metabolism and immunity-related genes. Starvation led to large tissue-specific changes in gene expression, but inbreeding had little effect on most of the genes studied. Our results illustrate the importance of studying stress responses in different tissues instead of entire organisms.
  • Sundström, Liselotte; Vitikainen, Emma (2022)
    With their sedentary colonies, long-lived ant colonies lend themselves to long-term studies where fitness effects of life-history traits can be investigated in the wild, a task that is challenging in any organism and particularly rarely feasible in insects. Here, we summarize and examine the insights we have gained from a 28-year study on monogyne colonies of the narrow-headed ant Formica exsecta NYLANDER, 1846, and discuss the ecological and genetic repercussions that emanate from ecological realities and conflicting selection pressures in a fragmented landscape matrix. These entail the effects of habitat structuration on genetic diversity, the effects of reduced genetic diversity on the fitness of individuals and colonies, and the impact of the opposing selection pressures on short-versus long-range dispersal.
  • Brommer, Jon E.; Kekkonen, Jaana; Wikström, Mikael (2015)
    A heterozygosity-fitness correlations (HFCs) may reflect inbreeding depression, but the extent to which they do so is debated. HFCs are particularly likely to occur after demographic disturbances such as population bottleneck or admixture. We here study HFC in an introduced and isolated ungulate population of white-tailed deer Odocoileus virginianus in Finland founded in 1934 by four individuals. A total of 4221-year-old white-tailed deer were collected in the 2012 hunting season in southern Finland and genotyped for 14 microsatellite loci. We find significant identity disequilibrium as estimated by g(2). Heterozygosity was positively associated with size- and age-corrected body mass, but not with jaw size or (in males) antler score. Because of the relatively high identity disequilibrium, heterozygosity of the marker panel explained 51% of variation in inbreeding. Inbreeding explained approximately 4% of the variation in body mass and is thus a minor, although significant source of variation in body mass in this population. The study of HFC is attractive for game- and conservation-oriented wildlife management because it presents an affordable and readily used approach for genetic monitoring that allowing identification of fitness costs associated with genetic substructuring in what may seem like a homogeneous population.