Chapter 11 Plasticity in phenotypic adaptation

Notes may not be my own language, as some sections were directly taken from the manuscripts I studied and are cited in the main header or in a parenthesis.

Fox et al 2018: Beyond buying time: the role of plasticity in phenotypic adaptation to rapid environmental change

Process of adaptation can occur via two mechanisms:
1. expression of phenotypic plasticity (happens at the individual level)
2. evolution via selection for particular phenotypes, resulting in the modification of genetic variation in the population

Phenotypic plasticity:
- rapid-response that could enable organisms to adapt and survive (also termed plastic rescue) OR
- this could also slow adaptation by shifting the distribution of phenotypes in a population closer to an optimum and shielding it from natural selection.

Not all phenotypes are adaptive; in the cases of ecological traps.

Four key themes

1. Need to measure plasticity across space and time
   
2. Importance of the past in predicting the future
   
3. Importance of the link between plasticity and sexual selection
   
4. Need to understand more about nature of selection on plasticity itself.

Debate is centered on:
- When plasticity is an adaptation = itself the result of evolution via natural selection OR
- When plasticity simply yields an adaptive outcome (i.e. fortuitously increases fitness)

My assumption was the second option above.. come back to think about how the first may be true…

This paper is about phenotypic plasticity relative to adaptive evolution in promoting adaptation to novel environments.

Different types of plasticity act on very different timescales
- Activational behavioral plasticity: high-cost, rapid response
- Developmental behavioral plasticity: low-cost, slower-acting with more integrated outcomes
- Transgenerational plasticity (TGP): slower timescale more on par with adaptive evolution

Big question: Is the type of plasticity relevant to the pace of environmental change?
Can’t assume that individual plasticity is always faster-acting than evolutionary

Evolutionary rescue vs. plastic rescue

come back to fill this in..

‘Matthew’ effect: initial advantages lead to further cumulative advantages.
- plasticity essentially functions as an amplifier for traits that already show condition-dependence, increasing the strength of the signal

Ecological trap: change towards a lower-quality environment, trigged by a decline in the reliability of the cue.

Genetic variation is known to be an important predictor of plastic and adaptive potential:
- Reduced genetic variation owing to strong positive selection or limitations on recruitment or migration can reduce the capacity for phenotypic plasticity
- OR traits that were once plastic can become fixed or expressed constitutively in the population (genetic assimilation)

The process of adaptation requires an increase in mean population fitness over time, so this requires the more fit phenotypes to mate with each other and/or often.

Sexual selection often results in healthier males having higher mating success, this should result in accelerated purging of mutations from the genome and an associated increased in female fitness through time.

Therefore, should promote adaptation to novel environments when:
- There is a positive genetic correlation between male sexual traits and female fitness,
- and if additive genetic variation persists under conditions of stress,
- and if these advantageous male traits are still reliable indicators of female fitness in the novel environment

Sexual selection isn’t always beneficial.

Plasticity may affect the strength and direction of sexual selection in novel environments.

“Physiological toolkit”: metabolic adjustments involve changes in the rates of energy uptake and allocation (i.e. metabolic rates) among competing function at the whole-organism level (i.e. maintenance, reproduction, growth, storage), which are conditioned by the capacity of mitochondria to provide sufficient aerobic energy at the cellular level (ATP).

Variation in metabolic rates:
- across time within individuals (i.e. owing to seasonal changes)
- among individuals (i.e. intra-population differences in energy demands)
- among populations (i.e. local adaptation)