Life History Evolution - 6 | Trans-generational effects

• Biologie
• Middelbare school

Adaptive plasticity and transgenerational effects

Piter Bijma

A genotype can change its phenotype based on environmental cues. This may occur across the generation border. 

This lecture is about:

-Plasticity and genotype by environment interaction

-GxE interaction is needed for plasticity to evolve

-Two types of transgenerational effects

-Four types of prenatal maternal effects

-Genetic mechanisms underlying transgenerational effects

Plasticity and genotype by environment interaction

GxE interaction is needed for plasticity to evolve

Two types of transgenerational effects

1.“Environment” dependent: environmentally transmitted

Poor maternal care > altered hormonal / neural regulation offspring > reduced reproductive capacity > negative effects development grand offspring

2.Germline dependent: transmitted with the genome

Poor maternal care > altered epigenetic regulation of genes in offspring’s body + germline  effect on grandoffspring

Cross fostering experiments necessary to disentangle these effects

Four types of prenatal maternal effects

Good early adaptation beneficial for fitness of both offspring and mother.

Fact: ● Maternal hormones affect embryonic development ● Maternal hormone levels are affected by her environment

Hypothesis: ● This is a message from mother to prepare her offspring for  their future environment

1.Anticipatory maternal effect

●Increase maternal fitness by increasing offspring fitness

2.Selfish maternal effect

●Increase maternal fitness at the expense of offspring fitness

3.Bet hedging maternal effect

●Reduce variance in maternal fitness by producing offspring with a range of phenotypes

4.Transmissive maternal effects

●Reduction in both maternal and offspring fitness

Genetic mechanisms underlying transgenerational effects

Slow

E.g. developmental plasticity

Adaptive plasticity

E.g. seasonal

Genetically permanent

"Transgenerational effects"

E.g. daphnia spike at birth

E.g. horses develop larger coat

Linear reaction norm --> linear gene environment to phenotype mapping
=Continuous phenotype (e.g. coat thickness)

Threshold genotype environment to phenotype mapping

=Discrete phenotype (e.g. two morphs)

Can plasticity evolve by natural selection?
If yes, then plasticity can be adaptive (serve fitness)

Evolution of plasticity requires genotypes to vary in plasticity

==> Plasticity can evolve only when there is GxE interaction

Is plasticity a good thing?

Adaptive plasticity: yes, it allows to maintain fitness

Not all phenotypic change due to change in E is favourable

Predictive Adaptive Response is a hypothesis that needs proof

Whats the name of the theory which suggests that the environment surrounding (due to nutritional alteration, hormonal fluctuations or exposure to toxins) the fetus during its developmental phase, plays a seminal role in determining its disease risk during the later stages?

- Changes in development that lead to greater disease risk;
- Genetic changes which alter disease risk;
-Epigenetic changes which alter disease risk of not only the child but also that of the next generation
i.e. after a famine, grandchildren of women who were pregnant during the famine, are born smaller than the normal size, despite nutritional deficiencies having been fulfilled.

1. fetal programming
2. prenatal programming

A biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence.

1. DNA Methylation
2. Anticipatory maternal effect
3. Prenatal programming
4. Phenotypic plasticity

A theory of evolution based on the principle that physical changes in organisms during their lifetime—such as greater development of an organ or a part through increased use—could be transmitted to their offspring.

1. Weismannism
2. Markov process
3. Lamarckism
4. Lack's principle

When two different genotypes respond to environmental variation in different ways.

1. Ageing
2. GxE- interaction
3. Bet-hedging maternal effect
4. environment dependent transgenerational effects