Coevolution I

Question 1

Describe biotic ‘environments’

Answer 1

can change rapidly and reciprocally

Question 2

Define coevolution

Answer 2

• change in the genetic composition of one species in response to a genetic change in another
• reciprocal evolutionary change in interacting species

Question 3

What is required for evolutionary change to occur?

Answer 3

1. Trait that confers fitness advantage
2. Genetic variation for that trait
3. Trait is heritable
4. Natural selection

Question 4

Tight ecological relationship =

Answer 4

specialisation

Question 5

List some ecological relationships that may coevolve

Answer 5

• predator/prey
• parasite/host
• mutualists
• competitors

Question 6

Coadaptation

Answer 6

reciprocal adaptations of two interacting species

Question 7

Lycaenid caterpillars x ant mutualism

Answer 7

• caterpillars secrete “honeydew” that ants drink
• ants defend caterpillars against parasitic wasps
• honeydew secretion and defence are co- adaptations

Question 8

Describe an example of predation coevolution

Answer 8

• crossbills prefer smaller cones; easier to get seeds out
• cone width, cone mass, and cone length have increased as a result
• crossbill beak size increased because of change in cone size
• divergence between crossbill populations for specialists and generalists

Question 9

Coevolution needs to be determined by

Answer 9

1) observation, 2) experiments, and 3) phylogenetic analysis.

Question 10

What are the co-evolutionary criteria?

Answer 10

• Fitness consequences?
• Specialisation?
• Genetic variation for heritable traits?
• Selection is reciprocal?

Question 11

Describe snails and trematodes

Answer 11

• expose shallow and deep snails to sympatric coevolving and allopatric non-evolving parasites
• measure infection prevalence
• parasites adapted to snails only in shallow and not in deep
• trematodes very good at infecting some snail genotypes
• host genetic background is changing over time

Question 12

Testing bacteria and phage coevolution

Answer 12

• Time Shift Assay
• bacteria from the past, present, and future (1 transfer difference) exposed to phage taken from a single transfer
• bacteria evolved increasing resistance to phage infection over time
• phages evolved to counter resistance