van der Werf / Graser / Frankham Adaptation and Fitness in Animal Populations

Evolutionary and Breeding Perspectives on Genetic Resource Management
1. Auflage 2008
ISBN: 978-1-4020-9005-9
Verlag: Springer Netherland
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 258 Seiten, eBook

Fitness and adaptation are fundamental characteristics of plant and animal species, enabling them to survive in their environment and to adapt to the inevitable changes in this environment. This is true for both the genetic resources of natural ecosystems as well as those used in agricultural production.Extensive genetic variation exists between varieties/breeds in a species and amongst individuals within breeds. This variation has developed over very long periods of time. A major ongoing challenge is how to best utilize this variation to meet short-term demands whilst also conserving it for longer-term possible use.Many animal breeding programs have led to increased performance for production traits but this has often been accompanied by reduced fitness. In addition, the global use of genetic resources prompts the question whether introduced genotypes are adapted to local production systems. Understanding the genetic nature of fitness and adaptation will enable us to better manage genetic resources allowing us to make efficient and sustainable decisions for the improvement or breeding of these resources.This book had an ambitious goal in bringing together a sample of the world’s leading scientists in animal breeding and evolutionary genetics to exchange knowledge to advance our understanding of these vital issues.

Zielgruppe

Research

Autoren/Hrsg.

van der Werf, Julius

Graser, Hans-Ulrich

Frankham, Richard

Gondro, Cedric

Inhaltsverzeichnis

Modelling Fitness.- Defining Fitness in Natural and Domesticated Populations.- Genetic Architecture of Reproductive Fitness and its Consequences.- Fitness Traits in Animal Breeding Programs.- Discussion.- Maintaining Fitness.- Maintaining Genetic Variation in Fitness.- Spherical Cows Grazing in Flatland: Constraints to Selection and Adaptation.- Maintaining Fitness by Within Breed Selection.- Discussion.- The Genetic Basis of Adaptation.- Some Evolutionary Consequences of Niche Construction with Genotype-Environment Interaction.- Genotype by Environment Interaction in Farm Animals.- Drosophila and Selection in Nature: From Laboratory Fitness Components to Field Assessments.- Discussion.- Strategies for Managing Diversity.- Strategies to Exploit Genetic Variation While Maintaining Diversity.- Managing Genetic Diversity, Fitness and Adaptation of Farm Animal Genetic Resources.- Livestock Genetic Resources: Preserving Genetic Adaptations for Future Use.- Discussion.- Concluding Summary.- Stuart Barker’s Contributions to Population Genetics and Animal Breeding: Exploring Fitness, Evolution and Animal Genetics.

Leseproben

Abstract How we should manage genetic diversity depends on why we want to manage it. The most generally useful strategy is to maintain variation across the genome, using methods that consider one or more of: population size, population structure, animal selections, mate allocations and information from genetic markers. A key reason to maintain genetic diversity is to facilitate longer-term genetic gains, and this means that most breeding programs need to consider genetic diversity as well as shorter-term genetic gains. This paper discusses these issues, and presents developments in methods to integrate genetic gains, genetic diversity and other issues within breeding programs.

Keywords Diversity · genetic variation · inbreeding · mate allocation

1 What is Genetic Variation?

This question seems quite easy to answer – genetic variation is the variation among individuals and/or populations in genetic constitution. In this context we often think of variation summed over single polymorphisms for mutations such as single nucleotide substitutions or small deletions. But we can move up the functional chain to consider co-variation among many polymorphisms, variation in functionality of biochemical pathways or other such biological networks, and on to variation in the impact of the whole (epi)genotype on phenotype in defined environments. Taking another angle, we can use genome-wide markers to make inference about genetic variation and maintenance of genetic variation, and their association with selection history as driven by fitness – without using explicit phenotypic information (e.g. Borevitz et al. 2007).

How we should define genetic variation depends on why we want to manage it, and the future opportunities we might have to exploit it. The less we know about these things, the more we resort to defining genetic variation in simple terms based, for example, on data from neutral genetic markers, and/or on population structure. Alternatively, if we want to manage genetic variation for a given trait in a given environment, we may elect to focus purely on the prevailing genetic component of variance for that trait, as derived from phenotypes and relationships.

Consider the somewhat optimistic scenario where we have conducted a genome scan for the population of interest, with sufficient genotypes and phenotypes to develop a reliable handle on QTL or marker associations that explain almost all of the genetic variation in a trait of interest. It is reasonably clear how to use this information to make early genetic gains in a breeding program. But how would we use this information to help maintain genetic variation for this trait? Driving towards intermediate or optimal allele frequencies across multiple loci would take many generations, especially if we are focusing on more loci because of attention to multiple traits. Assortative mating on genotypes to generate extra divergence would help reveal variation, making it more accessible later on, but again that takes many generations, and in fact extra variation is being unlocked, rather than created.