2: Coevolution

Question 1

Define coevolution

Answer 1

‘Reciprocal genetic change in interacting species, owing to natural selection imposed by each on the other’

Question 2

What is antagonism?
Give some examples

Answer 2

One species benefits, the other species incurs a cost

e.g predation, parasitism, herbivory

Question 3

Describe the Red queen dynamic in coevolution

Answer 3

Arms race: When one species evolves new adaptations, the other must also evolve to keep pace

Question 4

Define phylogenetic coevolution and give an example

Answer 4

Phylogenetic trees of 2 groups of species really closely match each other because they have such a tight evolutionary relationship

e.g Aphids and their symbiotic bacteria
- Began as parasites, but now mutualistic role
- Bacteria provide extra nutrients to the aphids (bc they feed on nutrient poor plant sap)

Question 5

Give some examples of Antagonism in Heliconius Butterflies and Passiflora

Answer 5

Passiflora adaptations:
1. Passiflora (passionflower) vines have toxins (cyanogenic compounds) in leaves
2. Leaf shape variation - to escape detection
3. Egg mimicry

Heliconius counter adaptations:
1. Heliconius caterpillars can detoxify and disable these compounds AND store them in their own tissues, for defence against their own predators.
2. Leaf shape is perceived by the butterflies and used in oviposition choice
= could drive antagonistic coevolution
3. Egg mimicry
Females Heliconius are picky about where they lay eggs
Caterpillars are healthiest when fed on young shoots - limited supply
Competition between individuals and species for host plants

Question 6

What are 2 outcomes of competition?

Answer 6

One species outcompetes other and drives them to extinction
OR
Competition results in adaptations that reduce competition = coexistence

Question 7

What is resource partitioning?

Answer 7

Over time, in competing species, natural selection drives each species to greater specialisation = partitioning the resource

Question 8

What is character displacement?

Answer 8

Character traits of 2 closely related species differ more in sympatric regions than in allopatric regions of their geographic ranges

Question 9

Define Mullerian mimicry

Answer 9

• Where warning signals in species with defences resemble each other
• So, predators learn more quickly to avoid harmful prey when multiple species exhibit similar warning signals