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Genetics of inherited variability

increasing uniformity by reducing competition

Marjanovic, Jovana (2018). Genetics of inherited variability. Diss. (sammanfattning/summary) Wageningen : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2018:16
ISBN 978-91-7760-172-2
eISBN 978-91-7760-173-9
[Doctoral thesis]

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Official URL: http://dx.doi.org/10.18174/442792


Social interactions are common for all living organisms. In animal breeding, these interactions are of interest as they are often a source of indirect genetic effects (IGEs). An IGE is a heritable effect of an individual on the trait value of another individual. In aquaculture populations and some plants, social interactions have an additional consequence – interactions in the form of competition inflate variability of trait values among individuals. The phenotypic variability of a genotype has been studied as a quantitative trait in itself, and is often referred to as inherited variability. The main objective of this thesis was to study the genetics of inherited variability, with a focus on the relationship between competition (i.e., IGEs) and variability.
In the thesis, we used Nile tilapia as a model species. We found that variability of body weight and body size traits in Nile tilapia is heritable, and shows a large genetic coefficient of variation, which offers good opportunities for improvement of uniformity by means of genetic selection.

To study the genetic relationship between social interactions and variability, we developed a quantitative genetic model that integrates both phenomena. In this model, interactions between social partners lead to divergence (competition) or convergence (cooperation) of their phenotypes (e.g., body weight) over their life time. The effects of social interaction in the model are heritable and can evolve. These effects comprise direct genetic effect of the focal individual and IGE of its social partner. With a simulation study we showed that the model yields increased variability of body weight with increase of competition, similar to what is observed in real aquaculture populations. Selection for cooperation will therefore lead to decreased variability. These findings suggest that IGEs may be creating an entire level of genetic variation in variability, that has so far been overlooked. Using existing statistical models, we show that direct genetic effects of competition on variability could be captured with a direct model of inherited variability, and similarly, IGEs of competition could be captured with an indirect model of inherited variability.

According to kin selection theory individuals should show better social behavior, i.e., less competition, towards relatives, which should be reflected in their body weight and the variability thereof. We tested this hypothesis by comparing two treatments in an experiment, in which tilapia were reared in either kin or in non-kin groups. Individuals had significantly higher body weight in kin groups, however, there was no difference in variability of body weight between the two treatments.

Findings of this thesis demonstrate that variability of body weight in tilapia is heritable and that genetic variation in variability may comprise not only direct genetic effects but also IGEs. Studies focusing on evolution of variability/uniformity, therefore, should consider IGEs.

Authors/Creators:Marjanovic, Jovana
Title:Genetics of inherited variability
Subtitle:increasing uniformity by reducing competition
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :6 April 2018
Depositing date:17 April 2018
Number of Pages:198
IMarjanovic J, Mulder HA, Khaw HL, Bijma P (2016). Genetic parameters for uniformity of harvest weight and body size traits in the GIFT strain of Nile tilapia. Genet Sel Evol 48: 41.
IIMarjanovic J, Mulder HA, Rönnegård L, Bijma P (in press). Modelling the co-evolution of indirect genetic effects and inherited variability. Heredity. doi: 10.1038/s41437-018-0068-z
IIIMarjanovic J, Mulder HA, Rönnegård L, Koning DJ, Bijma P. Capturing indirect genetic effects on phenotypic variability: Competition meets canalization. To be submitted.
IVMarjanovic J, Mulder HA, Khaw HL, Bijma P. Effects of relatedness between group mates on body weight and variability of body weight in domestic Nile tilapia. To be submitted.
Place of Publication:Wageningen
Publisher:Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-7760-172-2
ISBN for electronic version:978-91-7760-173-9
Additional Information:The research presented in this doctoral thesis was conducted under the joint auspices of the Swedish University of Agricultural Sciences and Wageningen Institute of Animal Sciences of Wageningen University & Research and is part of the Erasmus Mundus Joint Doctorate Program “EGS-ABG”.
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L10 Animal genetics and breeding
L Animal production > L20 Animal ecology
M Aquatic sciences and fisheries > M40 Aquatic ecology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Genetics (medical genetics to be 30107 and agricultural genetics to be 40402)
(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Evolutionary Biology
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Fish and Aquacultural Science
Agrovoc terms:tilapia, genetic inheritance, genetic variation, fish culture, behaviour, phenotypes
Keywords:Inherited variability, Uniformity, Competition, Indirect genetic effects, Social interactions, Canalization, Aquaculture, Nile tilapia, IGE
Permanent URL:
ID Code:15427
Faculty:VH - Faculty of Veterinary Medicine and Animal Science
Department:(VH) > Dept. of Animal Breeding and Genetics
External funders:European Graduate School in Animal Breeding and Genetics - Erasmus Mundus
Deposited By: Jovana Jovana Marjanovic
Deposited On:23 Apr 2018 13:31
Metadata Last Modified:09 Sep 2020 14:17

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