1. Local Adaptation: Conceptual bases Flashcards
Structure of the lecture
- Local Adaptatation
- Requirements for local adaptation
- Pattern vs., Process
- LA vs., PP
- Modelling LA
- Local Co-Adaptation
Define LA
1.1
LA is a phenomenon that occurs when the force of natural selection varies throughout space, as opposed to time. It results in resident genotypes having a higher fitness to the local environment compared to non-resident genotypes
Role of phenotypic variation in LA
1.2
Phenotypic variation is the natural variation that is required for LA to occur
What are the 5 requirements for LA?
2
- Weak, non-random gene flow
- Strong force of selection, facilitated by genetic architecture
- Little temporal variability between populations
- High chosts of phenotypic plasticity
- Strong linkage disequilibrium
What are the patterns of LA?
3.1
Understanding the variation in one species/spatial limits/migration/dispersal etc.,
Think about it like looking at a birds eye view of the populations
What are the processes involved in LA?
3.2
Speed, forces, directions etc.,
Why might pattern and processes of evolution not match?
3.3
Pattern and process often may not match when:
- There is inbreeding in one population
- When the same selective forces (pressures) are acting on both populations
What is the fundamental difference between PP and LA?
4.1
PP looks at the variation in phenotype across a habitat
LA looks at the variation in fitness across an environment
i.e., PP would be the variation in the how the pool of Oxford students look compared to Cambridge students. LA would be comparing their blood pressure (??) across the two
Is PP adaptive though?
4.2
It can be.
It will be adaptive if a plastic genotype performs better than a non-plastic one. But, this isn’t always the case.
When it is adaptive, it is called adaptive phenotypic plasticity
When does plasticity occur?
4.3
When environment changes on a shorter time scale than evolution
What is an example we can use to tease apart PP and LA?
4.4
Losos et al., 1994/1997/2000
Brown Anoles
Previously thought to have undergone rapid LA on islands with less vegetation
Then found to be PP according to perch thickness?
What are the two models of popgen in LA?
5
- Continent-Island (Haldane-Wright)
- Two-patch (Maynard-Smith, Bulmer)
Describe the Continent-Island model of LA?
5.1
There is a focal island population. LA occurs when selection on the island is greater than the migration to the island (Sa>Mb)
Describe the Two-Patch model of LA?
5.2
There are two identical patches, with migration occurring. LA will occur when Mb/Sa + Ma/Sb < 1
Can be extended to include things like asymmetries in population size, drift etc., but gets very complex very quickly
