Lecture 31 Flashcards Preview

Evolutionary Genetics and Genomics > Lecture 31 > Flashcards

Flashcards in Lecture 31 Deck (15):

Some kinds of stresses species experience:

- Human environmental modification
- Climate


Performance niche:

- The optimum temperature/aridity for a species to live in
- CTMin - Optimum - CTMax
(critical thermal)


Drought in the Australian alps:

- Increased environmental extremities, instead of 1 every hundred years, multiple in the past 15 years
- Altering the environment for species


- Evolution can decrease extinction risk and evolved responses are common:

- Bill size and shape in birds (galapogus finch)
- Thermal responses in ants
- Heavy metal and pesticide tolerance often evolves in non-target species


Adaptive variation under selection - we need:

- Variation
- Variation to have a genetic basis
- Fitness differences associated with variants
- And variation not accounted for by population processes


Population processes:

- Two populations separated for a couple of hundred generations
- The pattern in allele frequency and genetic diversity is related to origin
- We have to understand the origin of the populations, and if/when they split recently


Assessing adaption through clines:

- Clinical assessments
- Longitudinal studies of populations
- Gene isolation
- Conservation


What is a cline?

- A gradient in a trait or allele frequency that correlates with a gradient you are interested in
- Temperature
- Rainfall
- Elevation


Linear regression of lead length and plant circumference with altitude:

- Temperature, rainfall, soil moisture, UV radiation etc
- Using elevation as a resonal proxy for climate
- Skinny plants with long leaves at the base, short stout plants 200m higher
- Rule out population processes


Option 1 for testing:

- Compare patterns in traits with patterns in neutral markers, eg) microsatellites
- If neutral markers show same pattern, historical processes are probably responsible
- Test how the allele frequency relates to the latitude
- A neutral marker should show no significant relationship, but the selected allele should


Option 2:

- Indirectly test for selection on traits through parallel patterns across species/locations, expected patterns of selection
- Directly test for selection on traits through transplants, measurements of selection


Reciprocal transplant experiments:

- Plants are adapted to their certain mountainside and their elevation.
- This was determined by testing leaf length, with altitude and transplanting three high and three low elevation sites.
- This showed that plants from a high elevation site grow best at a high elevation site, and don't grow well at a low elevation site
- The circumference was also measured and a fitness curve was generated


Blackcap migraiton to overwintering sites:

- These birds migrate from Spain to the UK
- 10% of the birds started migrating to Germany around 10 years ago
- This was found to be genetically based
- Consequence of this change, UK migrants return earlier so they get more time to breed and find mates
- Could be the start of a speciation event


Shifting latitudinal clines in avian body size:

- Correlate with global warming in Australian passerines
- Wing length was measured as a proxy for body size
- Mean in body size decreases as they move further south, since 1950
- No time effect on nutritional status, so climate was likely to be a strong factor.


Genes underlying climatic adaptation can also show longitudinal shifts:

- Body colour
- Body size
- Also genes!
- Frequency of the AdhS allele decreases as you move further south
- This cline was the same over time, but the position of the cline has moved lower