Co-evolution Flashcards
Define co-evolution.
The evolution of reciprocal adaptations of 2 or more species that have prolonged close interactions
Co-evolution is expected in…
- mutualism (++)
- parasitism (+-)
- competition (–)
Co-evolution is unlikely in…
- commensalism (o+)
- amensalism (-o)
Give the 2 types of mimicry.
Mullerian & Batesian.
Define Mullerian mimicry.
- likely to exhibit reciprocal evolutionary patterns since both species involved are unpalatable and so have the opportunity to affect the evolution of each other’s colour patterns.
- the more abundant species is usually the model since it is what the selective agent (predator) is cueing on.
Define Batesian mimicry.
-may not involve co-evolutionary phenomena as the evolution of colour is asymmetric (one is unpalatable).
Define adaptive radiation.
spread of new species of common ancestry into different niches, involving an excess of cladogenesis over extinction
Define convergent evolution.
organisms not closely related. Independently evolve similar traits as aa result of having to adapt to similar environments or ecological niches.
What does diversification into different niches permit?
The coexistence of multiple species.
What are KEIs
Key evolutionary innovations, they drive diversification.
Factors that promote adaptive radiation.
INTRINSIC
-metabolic & physiological opportunities eg crassulacean acid metabolism, endosymbiosis, toxins.
-developmental opportunities eg Hox genes and segmentations, wings and flight, dispersal.
-efficient dispersal (some organisms lack the ability to disperse over wide ranges)
EXTRINSIC
-empty habitats
-novel environments
-intensity of selection
-founder effects
-ecological release – occurs when a species expands its niche within its own habitat or into a new habitat where there is little competition for resources, which remain abundant (also release from predators and disease).
Example of adaptive radiation.
Lake Malawi, ~400,000 years old (up to 2 million).
Single cichlid species >200,000 years ago has since diversified into approx. 1,000 different species
Give the model of vertebrate evolution based on lake Malawi Cichlids Streelman and Danley put forward.
- Divergence of lineages into different major habitats
- Morphological specialization leading to trophic differentiation within habitats
- Sensory communication diversification- sexual selection
Give 2 examples of convergent evolution.
- marsupial and placental mammals
- African euphorbias and north American cacti
Give an example of molecular convergent evolution.
-Antarctic fish vs Arctic fish
-Antarctic fish produce glycoproteins
-Arctic fish produce unrelated anti-freeze proteins
Independent episodes of molecular evolution occurred, with the same functional results.
Evidence of adaptive radiation.
homologous structure.
Evidence of convergent evolution.
analogous structure.
Limitations of convergent evolution.
- contingency
- functional/physical constraints
- developmental constraints
- genetic constraints
How can adaptive radiation be proved?
- a recent shared origin of members of the radiation
- an accordance between diverse genetically based phenotypic traits and their divergent environment
- a benefit of the specific phenotypic trait in the correlated environment
- relatively high rate of lineage splitting
- link between a key evolutionary innovation and rapid diversification
Fitness decides the outcome of selection, therefore adaptations are described in terms of
their ability to promote fitness
Give examples of fitness.
- viability
- growth
- foraging efficiency
- longevity
- fecundity
Give experimental approaches to adaptation.
Manipulate species -population size -variation (asexual vs sexual, in-breeding/outbreeding) -attributes (size, colour) -modify (biomimetics of a tail or wing) Manipulate environment -modify species composition -exclude or add predators/hosts -alter physical factors (temp, humidity)
Give a way to measure the contribution of an adaptive trait.
modify or inactivate it, then study the consequences for fitness
Why are microbes a good model for evolution?
- easily propagated
- rapid generation times
- large population sizes
- easily stored
- environment readily controlled
- asexual or sexual
- single or mixed gentype
- phenotypes are easily detected
- whole genome sequencing
- direct genetic manipulations possible
Summarise paper on adaptive radiation in a heterogenous environment
Stated aim: examine role of ecological opportunity and competition in driving genetic diversification.
Stated conclusions:
- ecological opportunities promote morphological diversification
- ecological homogeneity does not promote divergence
- mutation and selection alone are sufficient to promote new designs
- competition amongst niche variants maintains variation
- trade-offs in competitive ability drive adaptive radiation
