What is genetic diversity ? Training Workshop on Forest Biodiversity, Kuala Lumpur, Malaysia Thomas Geburek Department of Genetics Federal Research Centre.

What is genetic diversity ?

Training Workshop on Forest Biodiversity, Kuala Lumpur, Malaysia

Thomas Geburek

Department of GeneticsFederal Research Centre for Forests, Natural Hazards,

and Landscape (BFW)

Austria

Conditions for Forest Ecosystem Stability

• Species diversity• Temporal variation• Spatial variation• Patterns of interactions


Conditions for Forest Ecosystem Stability

• Species diversity• Temporal variation• Spatial variation• Patterns of interactions

• Genetic diversity


• material balance

• energy balance

• information balance

Ecosystem identity can be regarded as the totality of

Certain degree of constancy of the

information needed; must be of a

biological nature, and has its

material basis in the hereditary

substance DNA.



Noss (1990)

Biodiversity – genetic, species, and landscape level

Significance of genetic diversity

Adjustment to changing environmental conditions may be based on:

physiological adaptationinternal self-regulating mechanisms, the more

(allelic) genes the better the physiological buffer

epigenetic adaptationtriggered by environmental signals, not based on Mendelian inheritance, may regulate gene expression over generations

collective adaptationpopulation adjusts its genetic composition through evolutionary factors


Forest trees are something special

• Longevity

• Spatial heterogeneity


Pinus aristata

Pinus sylvestris

Mother Nature has equipped tree species with a high amount of genetic diversity necessary to cope with environmental changes in evolutionary time scales.

A long-term sustainable management of forest ecosystems requires the maintenance of genetic diversity in probably all tree populations.


Response functions of 10 Pinus sylvestris populations

Rehfeldt et al. (2002)


They are resulted from:

• reduction in population size

• loss, deterioration or fragmentation of habitats

• accelerated climate change

• population and species fragmentation

• introduced pathogens

• hybridization with nonnative species, and other detrimental factors

The fundamental problems of plant conservation genetics are loss of genetic diversity and harmful irreversible changes in population structure

Most (if not all) of these are due to human activity (such as habitat alteration, pollution, overexploitation, etc).


The major objective of conservation genetics

is to preserve the existing genetic diversity as potential for adaptation and evolution, and, therefore, to ensure that the adaptation and evolutionary potential of important regional tree species are maintained.

“Wild species must have available a pool of genetic diversity if they are to survive environmental pressures ….. If this is not the case, extinction would appear inevitable.”

(Otto Frankel 1983)


Key terms definition

• Genetic diversity (sensu lato) is the variety of alleles and genotypes present in a population, species or group of species.

• Genotype is the combination of alleles and genes in an organism.

• Phenotypic variation is the difference in morphology, physiology, or behavior among individuals of a species caused by genetic and environmental factors.

• Phenotype is the observed trait (physical, biochemical, behavioral, etc.) of an organism controlled by the interaction of its genes with the environment.


Genetic information is transmitted without chance to the next tree generation.

Uniparental inheritance


The vast majority of genetic information is maintained in the nucleus and is reshuffled from generation to generation.

Biparental inheritance

Where do we find genetic information ?

Individuals within a species may vary strongly phenotypically !


Source: http://www.biochem.wisc.edu/brassicaclassroomgenetics/index.html

Brassica wildtype

bushy dwarf

wrinkly



Genetic Markers

Nuclear genome in trees

• DNA content varies significantly in angiosperms (1000-fold size variation) and gymnosperms (14-fold size variation).

• Number of genes presumably varies between 30.000 und 50.000 covering 1.000 – 4.000 centi-Morgan.

• Hypothetical explanation: different amount of junk DNA (higher content of repeated DNA or single-copy, non-transcribed DNA).


Mitochondrial Genome

• Size varies between 200 kb and 2.500 kb, most often between 300 kb and 600 kb.

• characteristic large, highly variable repeats

• Recombination between repeats may form a complex genome (in it simpliest form a master and a slaves genome.

• 40 - 50 genes (mainly for respiration)


Chloroplast Genome

• Size varies between 120 (gymnosperms) and 150 kb (angiosperms).

• Approx. 100 to 120 genes (mainly for photosynthesis)

• Genes are tightly packed, large non-coding regions are missing.

• Order of genes is nearly identical among all plant species.

• Mutation rate is two up to threefold lesser than in the nuclear DNA and up to four times larger than in mt-DNA.


Gene: What is it?

5’ utr

3’ utr

DNA sequencer

gel image


Levels of genetic organization

Gene Text sequence

Chromosome Chapter

Genome

Genepool

Training Workshop on Forest Biodiversity, Kualar Lumpur, Malaysia 5-16 June 2006 Training Workshop on Forest Biodiversity, Kuala Lumpur, Malaysia

Sum of environmental factors:variation of the site in time and space,light, water, nutrients, etc

Phenotype

Sum of genetic information:30.000 – 50.000 genes (genotype)


How much genotype is in phenotype?


Organisms are different because of the

• genetic differences among individuals,

• different environments where individuals are growing, and

• interactions between genotypes and environments in which they exist.

P = G + E + G×E

Phenotype = Genotype + Environment + Interaction


How to separate between genetic and environmental effects?

Common Garden Experiment

Environment

Gene

Mixture of both


• provided insights into the adaptive variation of complex traits

• often geographical patterns, such as steep latitudinal or altitudinal clines

• time consuming and relatively expensive; solely based on the phenotypes

• can estimate genetic parameters on measurable traits

• can neither provide information on what particular genes and how many of them are involved in adaptation nor how much of phenotypic variation can be explained by genetic variation in these genes


Common garden experiments

Genetic diversity

(1) Quantitative genetic variation (genetic variances)

(2) Qualitative genetic diversity

information at single gene(s) must be available


additive variance ( = variances of the breeding values), non-additive genetic variance

• Variation within genes alleles & haplotypes

• Variation within individualsindividual heterozygosity

• Variation within populationsallele frequencies, average heterozygosity, average number of polymorphic alleles and loci and other summary statistics, effective number of alleles, pairwise individual genetic similarity or distance, etc

• Variation among populationsdifferentiation and genetic distance (pairwise and average)


How much genetic diversity is needed?

Peterson et al. (1998)

Darwin/MacArthur‘s Model Ehrlich & Ehrlich‘s „rivet“ Model

Walker‘s „driver and passenger“ ModelLawton‘s idiosyncratic Model


Oostermeijer et al. (2005)

Gentiana pneumonanthe

How much genetic diversity is needed?

The so-called Allee effect


By now you should know

...........


What is genetic diversity ? Training Workshop on Forest Biodiversity, Kuala Lumpur, Malaysia Thomas Geburek Department of Genetics Federal Research Centre.

Documents

forest biodiversity

malaysia slide

biodiversity genetic

kuala lumpur

loss of genetic diversity

forest trees

existing genetic diversity

pool of genetic diversity