Pigliucci - Phenotypic Plasticity

Front 1

Genotype phenotype mapping function
4 hypotheses

Back 1

1. Simple Mendelian model , "gene for x" model.
2. Characters controlled by
multiple genes, quantitative characters, pleitropy and epistasis.
Pleiotropy and epistasis make it more difficult to trace a phenotype
to a specific gene.
3. Plasticity model accounts for
environmental effects, genes respond to environmental cues.
4. pigenetics model. Includes. Development

Front 2

Pleiotropy

Back 2

one gene affecting several characters (or two linked
genes with joint inheritance).

Front 3

Epistasis

Back 3

One gene affects the action of another or others resulting in a complex genetic architecture.

Front 4

genotypic mean

Back 4

average phenotypic value across all environments, independent of plasticity of rx norm, depends on range of environments used in a given experiment

Front 5

Evolutionary potential for different rx norms

Back 5

genotypic mean varies (no plasticity): trait mean can evolve.
Genotypic mean varies (trait is plastic): only trait mean can evolve.
Genotypic mean and plasticity both vary: both can evolve.

Front 6

Broad sense vs. narrow sense heritability

Back 6

fill me in

Front 7

Genetic correlation

Back 7

fill me in

Front 8

Inter-environmental genetic correlation

Back 8

Considers the expression of one trait in multiple environments as different traits that are related by a degree of genetic correlation

Front 9

Causes of genetic correlation

Back 9

pleitropy: degree of genetic correlation is proportional to overlap in genetic control of the two traits. Positive correlation implies that genes have the same effects on both traits. Negative correlation may imply a trade-off.
Linkage: different genes are physically linked

Front 10

Evolutionary potential of two traits with pleitropy under the character state approach

Back 10

Positive correlation: selection favoring simultaneous increase or decrease in value can result in rapid evolution.
Negative correlation: if selection favors simultaneous increase or decrease, then evolution will be constrained.
Zero correlation: Allows for independent evolution of the traits - l

Front 11

Evolution of traits connected by pleitropy vs. linkage

Back 11

short term: same.
ong term: linkage will break down allowing independent evolution of the traits. Change in genetic system is required to decouple traits related by pleiotropy.

Front 12

Allelic sensitivity

Back 12

alleles that control a character can trigger distinct responses in different environments, e.g. enzyme kinetic
curves in relation to temperature or pH.

Front 13

Environment-dependent regulatory switches

Back 13

gene products that sense different environments and as a response mediate switches between two or more developmental pathways.

Front 14

Biological interpretation of inter-environmental correlation (rAE)

Back 14

within-environment genetic correlation (rG) of less than 1 for two
traits implies genetic variability, but rAE <1 can be the result of allelic sensitivity or environment-dependent regulatory switching. rAE is not informative about the genetic basis of a trait and is not a valid way to predict evolutionary trajectories for plasticity.