Browsing by Subject "heritability"

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  • Nichols, Hazel J.; Arbuckle, Kevin; Sanderson, Jennifer L.; Vitikainen, Emma I. K.; Marshall, Harry H.; Thompson, Faye J.; Cant, Michael A.; Wells, David A. (2021)
    Personality traits, such as the propensity to cooperate, are often inherited from parents to offspring, but the pathway of inheritance is unclear. Traits could be inherited via genetic or parental effects, or culturally via social learning from role models. However, these pathways are difficult to disentangle in natural systems as parents are usually the source of all of these effects. Here, we exploit natural 'cross fostering' in wild banded mongooses to investigate the inheritance of cooperative behaviour. Our analysis of 800 adult helpers over 21 years showed low but significant genetic heritability of cooperative personalities in males but not females. Cross fostering revealed little evidence of cultural heritability: offspring reared by particularly cooperative helpers did not become more cooperative themselves. Our results demonstrate that cooperative personalities are not always highly heritable in wild, and that the basis of behavioural traits can vary within a species (here, by sex).
  • Kemppainen, Petri; Husby, Arild (2018)
    A fundamental assumption in quantitative genetics is that traits are controlled by many loci of small effect. Using genomic data, this assumption can be tested using chromosome partitioning analyses, where the proportion of genetic variance for a trait explained by each chromosome (h(c)(2)), is regressed on its size. However, as h(c)(2)-estimates are necessarily positive (censoring) and the variance increases with chromosome size (heteroscedasticity), two fundamental assumptions of ordinary least squares (OLS) regression are violated. Using simulated and empirical data we demonstrate that these violations lead to incorrect inference of genetic architecture. The degree of bias depends mainly on the number of chromosomes and their size distribution and is therefore specific to the species; using published data across many different species we estimate that not accounting for this effect overall resulted in 28% false positives. We introduce a new and computationally efficient resampling method that corrects for inflation caused by heteroscedasticity and censoring and that works under a large range of dataset sizes and genetic architectures in empirical datasets. Our new method substantially improves the robustness of inferences from chromosome partitioning analyses.
  • Fraimout, Antoine; Li, Zitong; Sillanpää, Mikko J.; Merilä, Juha (2022)
    Heritable variation in traits under natural selection is a prerequisite for evolutionary response. While it is recognized that trait heritability may vary spatially and temporally depending on which environmental conditions traits are expressed under, less is known about the possibility that genetic variance contributing to the expected selection response in a given trait may vary at different stages of ontogeny. Specifically, whether different loci underlie the expression of a trait throughout development and thus providing an additional source of variation for selection to act on in the wild, is unclear. Here we show that body size, an important life-history trait, is heritable throughout ontogeny in the nine-spined stickleback (Pungitius pungitius). Nevertheless, both analyses of quantitative trait loci and genetic correlations across ages show that different chromosomes/loci contribute to this heritability in different ontogenic time-points. This suggests that body size can respond to selection at different stages of ontogeny but that this response is determined by different loci at different points of development. Hence, our study provides important results regarding our understanding of the genetics of ontogeny and opens an interesting avenue of research for studying age-specific genetic architecture as a source of non-parallel evolution.
  • Virtanen, Suvi (Helsingin yliopisto, 2017)
    There has been a steady increase in alcohol consumption in Finland since the 1969 law reform, which allowed convenience stores to sell mild alcoholic beverages such as beer. Since then, the yearly consumption has increased from 3.6 liters in 1968 to 10.8 liters of pure alcohol per capita in 2016. Increasing levels of alcohol use tend to produce high economic and population health costs. Understanding why changes in alcohol consumption behavior occur enables development of more efficient prevention and intervention programs. Alcohol consumption is not distributed equally across the population. Liberalization of Finnish alcohol policy and culture from the 1960s onwards made alcohol more available than ever before, and especially the post-war cohorts started to use significantly more alcohol than the generations before them. Evidently, there are between-individual differences in alcohol use in addition to group level differences. According to decades of research, approximately 50% of the variation between individuals in alcohol consumption can be explained by genetic sources. In other words, the heritability of alcohol use is 50%, while non-genetic factors explain the other half. However, heritability is not a static estimate, but can be modified by social forces. While it has been established that the younger generations consume significantly more alcohol than generations preceding them, only a few studies to date have examined whether the importance of genetic influences on alcohol consumption is dependent on birth cohort or generation. The current study examined, if social control during a specific time in history (e.g. how strict is alcohol policy and the cultural climate while a generation is growing up) can affect the heritability of alcohol use in later life. Mean level differences in alcohol consumption quantity and abstinence trajectories of birth cohorts were also estimated. The older Finnish twin cohort data consists of all Finnish same-sex twin pairs born before 1958 with both co-twins alive in 1975 (n = 24 481). The data were collected in four waves in 1975, 1981, 1990, and 2011. Age of the participants at study baseline in 1975 ranged from 18 to 95. Participants were grouped into seven 10-year cohorts based on their birth year. Mean trajectories of alcohol consumption quantity and abstinence over the life course were estimated for men and women separately with hierarchical growth curve models. Cohort effects and age-by-cohort interactions were also investigated. The heritability of alcohol consumption and abstinence was estimated using structural equation modelling. Birth cohort effects on heritability of alcohol use were examined by comparing heritability estimates of different cohorts at similar ages. Mean levels of alcohol consumption quantity were the highest in the youngest birth cohorts. Women drank less than men in all cohorts. The decline in the quantity of monthly alcohol use due to aging was relatively small, and appeared to be more prominent in the older birth cohorts. The odds of abstaining became lower in every successive birth cohort. Moreover, women were more likely to be abstinent than men. The aging effect of increasing abstinence was notable only in the oldest birth cohorts. Birth cohort differences in the heritability of alcohol consumption quantity were found: heritability was 25% (CI 12–38%) in the older generation (born 1901–1920) and 48% (CI 39–50%) in the younger generation (born 1941–1957) of men at the age of 54–74. For women, heritability was 60% in the older and younger generation. In alcohol abstinence, a single model was run for men and women. The shared environmental component explained a large proportion of the variation in the older generation (43%), whereas unique environment (54%) and additive genetic influences (40%) were more important among the younger generation. The findings from the present study suggest that social control during a specific time in history may have a long-term impact on alcohol consumption behavior (i.e. how and why alcohol is used) of an entire generation growing up during that period.
  • Virtanen, Suvi; Kaprio, Jaakko; Viken, Richard; Rose, Richard J.; Latvala, Antti (2019)
    Aims To estimate birth cohort effects on alcohol consumption and abstinence in Finland and to test differences between birth cohorts in genetic and environmental sources of variation in Finnish adult alcohol use. Design The Older Finnish Twin Cohort longitudinal survey study 1975-2011. Setting Finland. Participants A total of 26 121 same-sex twins aged 18-95 years (full twin pairs at baseline n = 11 608). Measurements Outcome variables were the quantity of alcohol consumption (g/month) and abstinence (drinking zero g/month). Predictor variables were 10-year birth cohort categories and socio-demographic covariates. In quantitative genetic models, two larger cohorts (born 1901-20 and 1945-57) were compared. Findings Multi-level models in both sexes indicated higher levels of alcohol consumption in more recent birth cohorts and lower levels in earlier cohorts, compared with twins born 1921-30 (all P < 0.003). Similarly, compared with twins born 1921-30, abstaining was more common in earlier and less common in more recent cohorts (all P < 0.05), with the exception of men born 1911-20. Birth cohort differences in the genetic and environmental variance components in alcohol consumption were found: heritability was 21% [95% confidence interval (CI) = 0-56%] in the earlier-born cohort of women [mean age 62.8, standard deviation (SD) = 5.3] and 51% (95% CI = 36-56%) in a more recent cohort (mean age 60.2, SD = 3.7) at the age of 54-74. For men, heritability was 39% (95% CI = 27-45%) in both cohorts. In alcohol abstinence, environmental influences shared between co-twins explained a large proportion of variation in the earlier-born cohort (43%, 95% CI = 23-63%), whereas non-shared environmental (54%, 95% CI = 39-72%) and additive genetic influences (40%, 95% CI = 13-61%) were more important among more recent cohorts of men and women. Conclusion The contribution of genetic and environmental variability to variability in alcohol consumption in the Finnish population appears to vary by birth cohort.
  • Leppaaho, Eemeli; Renvall, Hanna; Salmela, Elina; Kere, Juha; Salmelin, Riitta; Kaski, Samuel (2019)
    Brain structure and many brain functions are known to be genetically controlled, but direct links between neuroimaging measures and their underlying cellular-level determinants remain largely undiscovered. Here, we adopt a novel computational method for examining potential similarities in high-dimensional brain imaging data between siblings. We examine oscillatory brain activity measured with magnetoencephalography (MEG) in 201 healthy siblings and apply Bayesian reduced-rank regression to extract a low-dimensional representation of familial features in the participants' spectral power structure. Our results show that the structure of the overall spectral power at 1-90Hz is a highly conspicuous feature that not only relates siblings to each other but also has very high consistency within participants' own data, irrespective of the exact experimental state of the participant. The analysis is extended by seeking genetic associations for low-dimensional descriptions of the oscillatory brain activity. The observed variability in the MEG spectral power structure was associated with SDK1 (sidekick cell adhesion molecule 1) and suggestively with several other genes that function, for example, in brain development. The current results highlight the potential of sophisticated computational methods in combining molecular and neuroimaging levels for exploring brain functions, even for high-dimensional data limited to a few hundred participants.
  • Vatka, Emma; Orell, Markku; Rytkönen, Seppo; Merilä, Juha (2021)
    Many populations need to adapt to changing environmental conditions, such as warming climate. Changing conditions generate directional selection for traits critical for fitness. For evolutionary responses to occur, these traits need to be heritable. However, changes in environmental conditions can alter the amount of heritable variation a population expresses, making predictions about expected responses difficult. The aim of this study was to evaluate the effects of ambient temperatures on evolutionary potential and strength of natural selection on the timing of reproduction in two passerine birds breeding in boreal forests. Long-term data on individually marked Willow Tits Poecile montanus (1975-2018) and Great Tits Parus major (1969-2018) were analysed with random regression animal models to assess if spring temperatures affect the expressed amount of additive genetic variation (V-A) and heritability (h(2)) in the timing of breeding. We assessed if ambient temperatures of different seasons influenced the direction and strength of selection on breeding time. We also evaluated if the strength of selection covaried with evolutionary potential. Levels of V-A or h(2) expressed in laying date were unaffected by spring temperatures in both study species. Selection for earlier breeding was found in the Willow Tit, but not in the Great Tit. In the Willow Tit, selection for earlier breeding was more intense when the temperatures of following autumns and winters were low. Different measures of evolutionary potential did not covary strongly with the strength of selection in either species. We conclude that there is no or little evidence that climate warming would either constrain or promote evolutionary potential in timing of breeding through changes in amount of genetic variance expressed in boreal Willow and Great Tits. However, selection on the timing of breeding, a life-history event taking place in springtime, is regulated by temperatures of autumns and winters. Rapid warming of these periods have thus potential to reduce the rate of expected evolutionary response in reproductive timing.
  • Sarviaho, Katri (Helsingin yliopisto, 2019)
    The aim of this study was to estimate the genetic parameters of elk hunting traits in Jämthunds. There were nineteen traits under consideration. Heritabilities, repeatabilities, and genetic and phenotypic correlations were estimated for the traits. Also, coefficient of inbreeding and genetic trends were estimated. The data consisted of results from official elk hunting trials collected by Suomen Harmaahirvikoirajärjestö ry in 2012-2016. There were 46 221 results, from which 23 335 of Jämthunds. The pedigree data was provided by The Finnish Kennel Club and it included 31 544 Jämthunds. Significance of the fixed effects was estimated using F-test in analysis of variance with RStudio 1.0.136. The pedigree was pruned with RelaX2 1.54-pedigree analysis programme. Variance components were estimated with DMU-package using AI-REML-approach. The estimated heritabilities were low and varied between 0.00 and 0.047. The highest heritability was obtained for search and the lowest for obedience during work. Genetic correlations varied from -0.25 to 0.98, and the strongest were estimated for most of the bark related traits. The genetic trend has been positive in all traits, except for obedience traits. The coefficient of inbreeding for dogs born in 2016 was approximately 7.03 %, and the coefficient of inbreeding has decreased 0.26 % in the last decade. There are multiple non-genetic factors that affect the traits, and the data is based on subjectively evaluated variables. It is possible to improve genetic evaluation by collecting more information on trial conditions, by using the whole scale of points during the evaluation, and by making more objective evaluations of the traits. The estimated breeding values of the important traits can be used in selection of the parent of the next generation.
  • Kavlak, Alper T.; Uimari, Pekka (2019)
    Abstract A major proportion of the costs of pork production is related to feed. The feed conversion rate (FCR) or residual feed intake (RFI) is thus commonly included in breeding programmes. Feeding behaviour traits do not directly have economic value but, if correlated with production traits, can be used as auxiliary traits. The aim of this study was to estimate the heritability of feeding behaviour traits and their genetic correlations with production traits in the Finnish Yorkshire pig population. The data were available from 3,235 pigs. Feeding behaviour was measured as the number of visits per day (NVD), time spent in feeding per day (TPD), daily feed intake (DFI), time spent feeding per visit (TPV), feed intake per visit (FPV) and feed intake rate (FR). The test station phase was divided into five periods. Estimates of heritabilities of feeding behaviour traits varied from 0.17 to 0.47. Strong genetic correlations were obtained between behaviour traits in all periods. However, only DFI was strongly correlated with the production traits. Interestingly, a moderate positive genetic correlation was obtained between FR and backfat thickness (0.1?0.5) and between FR and average daily gain (0.3?0.4), depending on the period. Based on the results, there is no additional benefit from including feeding-related traits other than those commonly used (FCR and RFI) in the breeding programme. However, if correlated with animal welfare, the feeding behaviour traits could be valuable in the breeding programme.
  • Ruotanen, Päivi (Helsingin yliopisto, 2020)
    Patellar luxation is a typical orthopaedic disorder in small sized dogs. Patella can luxate either medially or laterally, medial luxation being by far more common than the lateral luxation. PL is considered hereditary since certain breeds have great susceptibility to get the condition, and the symptoms may occur at young age. PL is diagnosed by following the so-called Putnam’s scale where the stifle joint is palpated and manipulated. PL is graded from 0=normal…4=permanent luxation. The aim of this study was to estimate the variance components and the heritability of PL, to visualize PL’s genetic trend and to calculate the genetic correlation between left and right stifle and between PL and hip dysplasia (HD) in Japanese Spitz. The PL, HD and pedigree data were provided by the Finnish Kennel Club. Data were modified with both R-program and Microsoft Office Excel. The pedigree check was performed with RelaX2 program and variance component analyses were done with DMU program using the restricted maximum likelihood method. Heritabilities (h2) were from very low to low depending on the model and breed. When the dependent variable was the mean of left and right patellae of an individual the lowest heritability was in the Pomeranian h2=0.03 and highest in the Chihuahua h2=0.18. The genetic correlation of left and right patellae was 1 in all breeds which suggests that they are genetically the same trait. In the Japanese Spitz the genetic correlation between PL and HD was -0.05. The genetic trend of PL was favorable in the Chihuahua and the Japanese Spitz. In the Pomeranian the trend was negative and neutral in the Finnish Spitz. Based on the results, the selection against PL has not been efficient. In future, patellae health should be controlled by using breeding indexes because the heritability of PL is low. Also, improvements in phenotyping could lead to more accurate selection.
  • Salmela, Elina; Renvall, Hanna; Kujala, Jan; Hakosalo, Osmo; Illman, Mia; Vihla, Minna; Leinonen, Eira; Salmelin, Riitta; Kere, Juha (2016)
    Several functional and morphological brain measures are partly under genetic control. The identification of direct links between neuroimaging signals and corresponding genetic factors can reveal cellular-level mechanisms behind the measured macroscopic signals and contribute to the use of imaging signals as probes of genetic function. To uncover possible genetic determinants of the most prominent brain signal oscillation, the parieto-occipital 10-Hz alpha rhythm, we measured spontaneous brain activity with magnetoencephalography in 210 healthy siblings while the subjects were resting, with eyes closed and open. The reactivity of the alpha rhythm was quantified from the difference spectra between the two conditions. We focused on three measures: peak frequency, peak amplitude and the width of the main spectral peak. In accordance with earlier electroencephalography studies, spectral peak amplitude was highly heritable (h(2)>0.75). Variance component-based analysis of 28000 single-nucleotide polymorphism markers revealed linkage for both the width and the amplitude of the spectral peak. The strongest linkage was detected for the width of the spectral peak over the left parieto-occipital cortex on chromosome 10 (LOD=2.814, nominal P
  • Clemmensen, Signe B.; Harris, Jennifer R.; Mengel-From, Jonas; Bonat, Wagner H.; Frederiksen, Henrik; Kaprio, Jaakko; Hjelmborg, Jacob V. B. (2021)
    Simple Summary Hematologic malignancies account for 8-9% of all incident cancers. Both genetic and environmental risk factors contribute to cancer development, but it is unclear if there is shared heritability between hematologic malignancies. This study aimed to investigate familial predisposition to hematologic malignancies using the largest twin study of cancer in the world. We compared individual risk in the general population and the risk of cancer in one twin before some age given that the other twin had (another) cancer before that age. Furthermore, by analyzing information about whether the twins were identical or fraternal, we could estimate the relative importance of genetic and environmental influences on the risk for developing hematologic cancers. This study confirmed previous findings of familial predisposition to hematologic malignancies and provides novel evidence that familial predisposition decreases with increasing age. The latter points to the importance of taking age into account in the surveillance of hematological cancers. We aimed to explore the genetic and environmental contributions to variation in the risk of hematologic malignancies and characterize familial dependence within and across hematologic malignancies. The study base included 316,397 individual twins from the Nordic Twin Study of Cancer with a median of 41 years of follow-up: 88,618 (28%) of the twins were monozygotic, and 3459 hematologic malignancies were reported. We estimated the cumulative incidence by age, familial risk, and genetic and environmental variance components of hematologic malignancies accounting for competing risk of death. The lifetime risk of any hematologic malignancy was 2.5% (95% CI 2.4-2.6%), as in the background population. This risk was elevated to 4.5% (95% CI 3.1-6.5%) conditional on hematologic malignancy in a dizygotic co-twin and was even greater at 7.6% (95% CI 4.8-11.8%) if a monozygotic co-twin had a hematologic malignancy. Heritability of the liability to develop any hematologic malignancy was 24% (95% CI 14-33%). This estimate decreased across age, from approximately 55% at age 40 to about 20-25% after age 55, when it seems to stabilize. In this largest ever studied twin cohort with the longest follow-up, we found evidence for familial risk of hematologic malignancies. The discovery of decreasing familial predisposition with increasing age underscores the importance of cancer surveillance in families with hematological malignancies.
  • Hatton, Sean N.; Panizzon, Matthew S.; Vuoksimaa, Eero; Hagler, Donald J.; Fennema-Notestine, Christine; Rinker, Daniel; Eyler, Lisa T.; Franz, Carol E.; Lyons, Michael J.; Neale, Michael C.; Tsuang, Ming T.; Dale, Anders M.; Kremen, William S. (2018)
    Two basic neuroimaging-based characterizations of white matter tracts are the magnitude of water diffusion along the principal tract orientation (axial diffusivity, AD) and water diffusion perpendicular to the principal orientation (radial diffusivity, RD). It is generally accepted that decreases in AD reflect disorganization, damage, or loss of axons, whereas increases in RD are indicative of disruptions to the myelin sheath. Previous reports have detailed the heritability of individual AD and RD measures, but have not examined the extent to which the same or different genetic or environmental factors influence these two phenotypes (except for corpus callosum). We implemented bivariate twin analyses to examine the shared and independent genetic influences on AD and RD. In the Vietnam Era Twin Study of Aging, 393 men (mean age = 61.8 years, SD = 2.6) underwent diffusion-weighted magnetic resonance imaging. We derived fractional anisotropy (FA), mean diffusivity (MD), AD, and RD estimates for 11 major bilateral white matter tracts and the mid-hemispheric corpus callosum, forceps major, and forceps minor. Separately, AD and RD were each highly heritable. In about three-quarters of the tracts, genetic correlations between AD and RD were >.50 (median = .67) and showed both unique and common variance. Genetic variance of FA and MD were predominately explained by RD over AD. These findings are important for informing genetic association studies of axonal coherence/damage and myelination/demyelination. Thus, genetic studies would benefit from examining the shared and unique contributions of AD and RD.
  • Ajayi, Busayo (Helsingin yliopisto, 2019)
    The Finnish dairy cattle population has been subjected to systematic quantitative studies over decades. The Western Finncattle (WFC) has evolved over the last century with a production level comparable to other remaining local breeds in Europe. The heritability is used in designing the data collection and in predicting the changes expected from the selection and the variation parameters are used in constructing the economic selection indices genetic improvement scheme and in computing the bulls’ and cows’ breeding values. WFC has no recent studies on the genetic variation in milk production traits. The thesis research was set to estimate the heritability of milk, fat and protein yield, fat%, protein%, protein-fat ratio and somatic cell count (SCC) and the genetic correlation amongst them. Records from Western Finncattle primiparous cows calving in the period 2002–2016 were used for the genetic analyses. The raw data consisted of 5455 cows distributed across 2512 herds. The variance components were estimated with single and multi-trait animal model using a Bayesian approach and R studio package MCMCglmm. With requiring at least 5 cows in each herd-year subclass in the estimation, the data size was reduced to 1763 cows in 233 herds. The heritability of milk, protein and fat yield, protein%, fat% and SCC was in single (and in brackets for multi) trait analysis 0.36 (0.37), 027(0.30), 0.32 (0.30), 0.61(0.43), 0.52 (0.49) and 0.06 (0.15), respectively. Amongst yield traits and also between the content traits the genetic correlation was high, 0.73–0.94 and 0.43–0.59, respectively. The content traits (with milk yield in the denominator) had a negative genetic correlation with milk yield while no correlation with the protein and fat yield. There was an environmental correlation between content and yield traits for protein and fat. No correlations exist between SCC and other traits except an environmental correlation with milk yield and protein content. Despite the small population size of the WFC population, the effective population size is satisfactory and therefore no reduction in genetic variation is expected. Overall, the analysis on production traits and pedigree data shows that the Western Finncattle have much potential for genetic improvement.
  • Saastamoinen, Marjo Anna Kaarina; Bocedi, Greta; Cote, Julien; Legrand, Dephine; Guillaume, Fredric; Wheat, Christopher West; Fronhofer, Emanuel A.; Garcia, Cristina; Henry, Roslyn; Husby, Arild; Baguette, Michelle; Bonte, Dries; Coulon, Aurelie; Kokko, Hanna; Matthysen, Erik; Niitepöld, Kristjan; Nonaka, Etsuko; Stevens , Virginie M.; Travis, Justin MJ; Donohue, Kathlin; Bullock, James M.; del Mar Delgado, Maria (2018)
    Dispersal is a process of central importance for the ecological and evolutionary dynamics of populations and communities, because of its diverse consequences for gene flow and demography. It is subject to evolutionary change, which begs the question, what is the genetic basis of this potentially complex trait? To address this question, we (i) review the empirical literature on the genetic basis of dispersal, (ii) explore how theoretical investigations of the evolution of dispersal have represented the genetics of dispersal, and (iii) discuss how the genetic basis of dispersal influences theoretical predictions of the evolution of dispersal and potential consequences. Dispersal has a detectable genetic basis in many organisms, from bacteria to plants and animals. Generally, there is evidence for significant genetic variation for dispersal or dispersal-related phenotypes or evidence for the micro-evolution of dispersal in natural populations. Dispersal is typically the outcome of several interacting traits, and this complexity is reflected in its genetic architecture: while some genes of moderate to large effect can influence certain aspects of dispersal, dispersal traits are typically polygenic. Correlations among dispersal traits as well as between dispersal traits and other traits under selection are common, and the genetic basis of dispersal can be highly environment-dependent. By contrast, models have historically considered a highly simplified genetic architecture of dispersal. It is only recently that models have started to consider multiple loci influencing dispersal, as well as non-additive effects such as dominance and epistasis, showing that the genetic basis of dispersal can influence evolutionary rates and outcomes, especially under non-equilibrium conditions. For example, the number of loci controlling dispersal can influence projected rates of dispersal evolution during range shifts and corresponding demographic impacts. Incorporating more realism in the genetic architecture of dispersal is thus necessary to enable models to move beyond the purely theoretical towards making more useful predictions of evolutionary and ecological dynamics under current and future environmental conditions. To inform these advances, empirical studies need to answer outstanding questions concerning whether specific genes underlie dispersal variation, the genetic architecture of context-dependent dispersal phenotypes and behaviours, and correlations among dispersal and other traits.
  • Paaso, Ulla; Keski-Saari, Sarita; Keinänen, Markku; Karvinen, Heini; Silfver, Tarja; Rousi, Matti; Mikola, Juha (2017)
    Abundant secondary metabolites, such as condensed tannins, and their interpopulation genotypic variation can remain through plant leaf senescence and affect litter decomposition. Whether the intrapopulation genotypic variation of a more diverse assortment of secondary metabolites equally persists through leaf senescence and litter decomposition is not well understood. We analyzed concentrations of intracellular phenolics, epicuticular flavonoid aglycones, epicuticular triterpenoids, condensed tannins, and lignin in green leaves, senescent leaves and partly decomposed litter of silver birch, Betula pendula. Broad-sense heritability (H-2) and coefficient of genotypic variation (CVG) were estimated for metabolites in senescent leaves and litter using 19 genotypes selected from a B. pendula population in southern Finland. We found that most of the secondary metabolites remained through senescence and decomposition and that their persistence was related to their chemical properties. Intrapopulation H-2 and CVG for intracellular phenolics, epicuticular flavonoid aglycones and condensed tannins were high and remarkably, increased from senescent leaves to decomposed litter. The rank of genotypes in metabolite concentrations was persistent through litter decomposition. Lignin was an exception, however, with a diminishing genotypic variation during decomposition, and the concentrations of lignin and condensed tannins had a negative genotypic correlation in the senescent leaves. Our results show that secondary metabolites and their intrapopulation genotypic variation can for the most part remain through leaf senescence and early decomposition, which is a prerequisite for initial litter quality to predict variation in litter decomposition rates. Persistent genotypic variation also opens an avenue for selection to impact litter decomposition in B. pendula populations through acting on their green foliage secondary chemistry. The negative genotypic correlations and diminishing heritability of lignin concentrations may, however, counteract this process.
  • Häkli, Katja (Helsingfors universitet, 2013)
    The objective of this study was to estimate genetic parameters of minks Aleutian Disease (AD) infections and investigate the genetic relationships between Aleutian Disease infection and fertility traits. The research data was obtained from the Finnish Fur Breeders Association. The data had information from one mink farm in years 2006-2010. The data contained 27 753 one year old female minks. Only those females who had more than three kits were tested. There were 18 478 tested minks of which 9.2 % had AD. The pedigree data had 41 573 animals. In this study AD infection, pregnancy and felicity were binary traits. AD inf. 1 = sick, 2 = healthy. If female had kit(s) or aborted or lost her kit(s) after birth, pregnancy (PREG) = 2, otherwise = 1. If female lost her kits after birth, felicity (FEL) = 1. If litter size were at least one, FEL = 2. The heritability estimates and variance components (REML) were calculated using multi trait animal model and DMU-software. Heritability estimates for the studied traits were low: 0.07 for AD infection, 0.07 for PREG, 0.04 for FEL and 0.08 for litter size. The heritability estimate for AD was smaller than the common litter variance for the trait. Genetic correlations between AD inf. and FEL, and AD inf. and litter size were positive. The genetic correlations between AD inf. and FEL were 0.447 ± 0.132 and between AD inf. and litter size 0.290 ± 0.108. The results suggest that resistance for AD inf. has genetic variation. Although the heritability estimate for the trait was low, it can be affected by selection. Genetic correlations between AD inf. and fertility traits were favourable. Selection for larger litter size could increase mink resistance for AD infection.
  • Tigerstedt, P. M. A. (Suomen metsätieteellinen seura, 1969)