The Ecology and Geography of Coevolution

Concepts + case studies

Bob Week - BIOL227 - Kiel University

Follow Along!

Interactive slides available at:

https://bobweek.github.io/teaching/coevolution_intro/lecture.html

Many uses of the word Coevolution

A magazine from the 70s

but …

The most important and coolest meaning is

Coevolution of two (or more) species due to ecological interactions

Interspecific Coevolution is a Massive Topic

Host-parasite coevolution
Major transitions of evolution
- Mutualism from parasitism
- Evolution of recombination / sexual reproduction
Structure and stability of mutualistic networks
- Plant-pollinator, fruit-frugivore
Competition and coexistence
- Resource partitioning, character displacement, range dynamics
Local Adaptation
- Spatial variation, specialization, speciation
- Genomic and phenotypic signatures of coevolution

Roadmap

Act I: What is coevolution?

Definitions
Representative forms of coevolution

Act II: The ecology of coevolution

Coevolutionary outcomes of ecological interactions
Ecological outcomes of coevolutionary dynamics (ie, eco-evo feedback!)
The community context

~~Act III: The geography of coevolution~~

~~Spatial structure of ecological interactions~~
~~Determinants of host-parasite local adaptation~~
~~The spatial signature of coevolution~~

Learning Outcomes

Define coevolution precisely (and say what it is not)
Recognize how coevolution can maintain genetic diversity
Explain how ecology and coevolution feedback on each other

Act I: What is coevolution?

Conditions for Coevolution

DEFINITION: Coevolution occurs when

the interaction between a pair of species alters selection pressures on both species and

both species exhibit an evolutionary response to the altered selection pressures

Review:

What is selection?

What is an evolutionary response to selection?

Read:

“When is it coevolution?”, Janzen 1980

Selection Review (see Lande & Arnold, 1983)

DEFINITION: Selection occurs when fitness and phenotype covary

DEFINITION: A phenotype is any measurable attribute of an organism

DEFINITION: Fitness is the lifetime reproductive output of an individual

Adaptation the Evolutionary Response to selection

DEFINITION: Adaptation is the inherited/evolutionary resposne to selection

Coevolution is Co-adaptation

Coevolution ⇔ both species adapt in response to selection caused by interaction

Examples of Coevolution: Character Displacement

Interaction type: resource competition along a continuous niche axis
Altered selection: divergent resource use/specialization (directional selection)
Coevolutionary response: both species evolve to reduce resource competition

Examples of Coevolution: Mutualistic Matching

Interaction type: mutualism w trait-matching (eg, plant-poll. phenology)
Altered selection: positive freq. dependent selection (stabilizing selection)
Coevolutionary response: loss of polymorphism (decr. genetic variation)

Examples of Coevolution: Trench Warfare

Interaction type: host-parasite w lock-key (eg, viral receptor binding)
Altered selection: negative freq. dependent selection (diversifying selection)
Coevolutionary response: maintenance of polymorphism (incr. genetic variation)