Talking about biodiversity and how it affects our environment surrounded us

1. Biodiversity

2. Sun and Wu 2015_Physics of life Reviews
Transpiration exceeds water uptake
Drought tolerance  water use efficiency
Drought escape  early flowering
Drought avoidance
Minimize water loss  stomatal closure
Maximize water uptake  increased root to
shoot ratio
Adaptive strategies to drought

3. To meet natural changes of the environment, it is essential that
populations can cope with the imposed stresses at both the
short-term and the long-term.
Short-term the initial tolerance and the adaptive plastic response
(phenotypic plasticity) are decisive parameters.
Long-term evolutionary adaptive responses are of paramount
importance.
As we are mostly dealing with short or intermediate time scales,
rare beneficial mutations will be uncommon and consequently
the evolutionary response will mainly depend on the standing
genetic variation.

4. Hence, the ability to cope and adapt to changing conditions will
depend both on how well individuals can adjust to the new
conditions and on the amount of genetic variation for relevant
fitness traits available for evolutionary responses.
Knowledge of the causes, mechanistic underpinnings and
consequences of phenotypic plasticity and the capacity of a
genotype to produce different phenotypes in response to
environmental variation is crucial for a better understanding of the
evolution and for the maintenance of biodiversity
Forsman 2015, Heredity

5. Greater diversity leads to greater ecosystem stability, greater
resistance to invasion by exotic species, and lower disease
incidence (Elton 1958)

6. 1. Species diversity: the genetic variation found between species
in a given ecosystem
2. Genetic diversity: the genetic variation found within species
3. Ecosystem diversity: the variety of habitat type over a given
region
Three Scales of Biological biodiversity

7. 1- Levels of Genetic Diversity
a. Allelic diversity, different variants of the same gene
1. A single letter (SNP) in the sequence is swapped for another letter
2. One or more letters are inserted into a sequence
3. One or more letters are missing from a sequence
Some variants are beneficial, some are harmful
b. Entire genes diversity

8. A single nucleotide polymorphism (SNP) is a base site (one letter
in the genetic code) that differs among individuals in a
population.
Analysis of SNPs in populations (comparing SNPs between
persons with and without a trait of interest) can provide clues to
genetic variants associated with traits.
Sometimes the SNP itself is associated with the trait of interest,
but often the SNP is only a marker nearby the actual causal
variant.
SNPs have also been used in studies of origins and race.

9. c. Chromosomal level
1- Levels of Genetic Diversity
Changes in the number and/or structure of chromosomes
causing abundant changes in the amount of DNA present in
the cell
Number: Down syndrome results from the presence of an
extra chromosome 21.
Structure: deletion, duplication, inversion or translocation
of chromosomal segments. May lead to Copy Number
Variation (schizophrenia, autism-spectrum disorders )

10. DNA methylation: addition of a methyl group to a piece of
DNA, which holds the DNA in its condensed chromosome form,
effectively inactivating the sequence at that location.
Histone modification: In the formation of the chromosome,
DNA winds around proteins called histones. Modifications of
the protein affect the ability of DNA to come in and out of
chromosome form.
1- Levels of Genetic Diversity
d. Epigenetic level

11. 1- Levels of Genetic Diversity
Epigenetic level
Epigenetic factors may act on whole chromosomes, segments of
DNA, RNA, or even proteins and affects whether these molecules
are available for the transcription or translation process.
Epigenetic factors vary from individual to individual based both
on their genetic makeup and on their environmental
exposures.
Specific genes may have different effects at different times in the
lifespan

12. Plasticity often involves altering gene expression and plant
physiology in response to environmental cues.
Technological advances in genotyping approaches have resulted in
a shift in the focus of plant-breeding research from the generation
of molecular markers, which is no longer an issue, to high-
throughput, automated phenotyping.
It is becoming easy to determine how environmental factors affect
the phenotype and, hence, to better understand phenotypic
plasticity.

13. Phenotypic plasticity and genotype x environment interaction (G x E).
Four examples of reaction norms illustrating
Plasticity: best performing genotype in one environment remain the best
performing in other environments
GxE: natural variation in plasticity “crossover of reaction norms”
Genotype 1 is the red line and genotype 2 is the blue line in each graph

14. Phenotypic plasticity: the ability of a genotype to produce
distinct phenotypes in different environments.
Genotype x environment interaction (G x E): different
relative performance of two or more genotypes in different
environments causing nonparallel or crossing reaction norms

15. Genetic models underlying G x E:
overdominance Pleiotropy
Epistasis Linkage
Epigenesis

16. Genetic models underlying G x E:
Five genetic models or mechanisms have been proposed to
explain the genetic basis of G x E
A. Over-dominance: The more heterozygote the plant, the more
homeostatic it is.
B. Pleiotropy or allelic sensitivity: a pleiotropic gene affects two
traits and may have different effects in different
environments.
C. Epistasis: loci confering plasticity may modify the expression
of other genes to be turned on or off in an environment-
specific fashion.

17. Genetic models underlying G x E:
Five genetic models or mechanisms have been proposed to explain
the genetic basis of G x E
D. Genetic linkage: alleles promoting plasticity may be linked with
alleles conferring either low or high fitness.
E. Epigenesis: the impact of chromatin modification and DNA
methylation may depend on the environment, without changing
the DNA sequence

18. Fitness trade-offs, environmental antagonistic pleiotropy,
and G x E
Evolutionary biologists have long recognized that traits
improving fitness in local environments can have neutral
effects or even be deleterious in nonlocal environments, thus
explaining apparent fitness trade-offs between environments.
One of the mechanisms underlying trade-offs is environmental
antagonistic pleiotropy.

19. Examples of antagonistic pleiotropy
1. Studying the effects of polymorphisms of the flowering time
gene FRIGIDA (FRI) on fitness, described as the number of
fruits per plant.
In an experiment involving intercrosses of19 Arabidopsis
accessions, FRI loss of function was found to contribute to early
flowering, however, this allele had a pleiotropic effect on branch
number, which was the major predictor of fruit set.

20. Examples of epistasis and antagonistic pleiotropy
2. Epistasis between FRI and FLOWERING LOCUS C (FLC) had an
effect on plant survival in different environments.
• Autumn germinating Arabidopsis accessions with a functional
FRI allele showed higher winter survival in the FLCA allelic
background
• Spring germinating accessions with a fri null allele had greater
seed production in the FLCB allelic background.

21. Examples of antagonistic pleiotropy
3. An example of trade-offs of ACCELERATED CELL DEATH 6 (ACD6) gene that is
present in approximately 20% of all Arabidopsis.
Although this allele slows down plant growth, its pleiotropic effect causes an
increase in plant resistance to pathogens
4. Another study reported single nucleotide polymorphisms (SNPs) associated
with two genes:
CHROMATIN REMODELING 8 (CHR8), which functions in DNA repair after viral
infection, and
SENESCENCE-ASSOCIATED GENE 21 (SAG21), which functions in water stress
tolerance.
A specific CHR8 allele was associated with survival in Germany, although it was
mainly distributed in the northern range of the species,
SAG21 allele was associated with survival in Finland, although it was more
abundant in the southern distribution range.

22. Thank you for your attention