Genetics - co-evolution, convergent evolution, adaptive radiation

What is co-evolution?

Evolution of reciprocal adaptations of two or more species that have prolonged close interactions

In which kind of situations are co-evolution expected?

• Mutualism

• Parasitism or predation

• Competition

In what situations is co-evolution unlikely?

• Commensalism

• Amenalism

What is the red queen hypothesis?

• Biotic and abiotic world is constantly changing causing shifts to adaptive peaks

• Each species in an ecosystem is engaged in a permanent race with other

• Success for one inevitably means a decline for others

What is a biological arms race?

Situation where an innovation in one species leads to a counter innovation in the other

What model did host-pathogen interactions help produce?

Gene-for-gene model

What are the two types of mimicry?

• Mullerian mimicry

• Batesian mimicry

How do Mullerian mimics utilise co-evolution?

• Likely to exhibit reciprocal evolutionary patterns as both species involved are unpalatable and have an opportunity to affect the evolution of each other’s colour patterns

• More abundant species is usually the model as it is what the selective agent is cueing on

How do Batesian mimics utilise co-evolution?

• May not involve co-evolutionary phenomena since the evolution of warning colouration is asymmetric

• First noted in Brazilian butterflies where a palatable species ‘parasitises’ the warning without having to arm itself

• Dishonest signals are found in many species pairs

• Good example of frequency-dependent selection

What is adaptive radiation?

Describes the spread of new species of common ancestry into different niches, involving an excess of cladogenesis over extinction

How does adaptive radiation occur?

• Diversification into different ecological niches permits the coexistence of multiple species

• All major groups have undergone adaptive radiation

• Easily noticed in geographically isolated environments

• Founder species will diversify to occupy available niches

What factors allow diversification in adaptive radiation?

• Key evolutionary innovations

• Intrinsic - metabolic and physiological opportunities; developmental opportunities

• Extrinsic - empty habitats (no competition); novel environments; intensity of selection; founder effects

What is ecological release?

A species expands its niche within its own habitat or into a new habitat where there is little competition for resources that remain abundant

What was Steelman and Danley’s model of vertebrate evolution?

• Divergence of lineages into different major habitats

• Morphological specialization leading to trophic differentiation within habitats

• Sensory communication diversification

What is convergent evolution?

Process where organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches

How do Arctic and Antarctic fish show convergent evolution?

• Both produce antifreeze to stop them freezing

• Antarctic fish produce glycoproteins

• Arctic fish produce unrelated antifreeze proteins

• Show independent episodes of molecular evolution occurring with the same functional results - analogous genes

What are the limitations of convergent evolution?

• Contingency

• Functional/physical constraints

• Developmental constraints

• Genetic constraints

What do homologous and analogous structures show?

• Homologous structures show adaptive radiation

• Analogous structures show convergent radiation