Lecture 16 - Co-evolution

Question 1

Coevolution

Answer 1

Evolution in two or more evolutionary entities brought about by reciprocal selective effects between entities

Question 2

How does coevolution differ from regular evolution?

Answer 2

Mutual responses between organisms - in evolution in response to the environment the environment does not respond in turn

Promotes diversity of adaptations - Reciprocal responses involve specific unique responses to particular challenges

Question 3

What are the 4 antagonistic interactions in coevolutionary dynamics

Answer 3

Predation

Herbivory

Competition

Parasitism

Question 4

Red queen hypothesis

Answer 4

In coevolution both organisms evolve reciprocally but neither animal evolves away from each other

Question 5

What are the four outcomes of enemy-victim coevolution?

Answer 5

Continue indefinitely in an unending escalation of an evolutionary arms race

Results in stable genetic equilibrium

Cause continual cycles (or irregular fluctuations) in the genetic composition of both species

Eventual extinction of both species

Question 6

What are the conditions for coevolution?

Answer 6

Genetic variation for the relevant enemy and victim traits

Reciprocal effects of the traits involved on the fitness of individuals (of each species)

Dependence of the outcome of the enemy-victim interaction on the combination of the particular traits involved

Question 7

Coevolution in the Predation sequence

Answer 7

The predation sequence is a sequence of events in predation that result in the escape of the prey of death of the prey

Adaptations can evolve to maximise survival (prey) or successful capture and consumption (predator) at different stages in the predation sequence

Question 8

What are the 3 different catagories of coevolutionary dynamics?

Answer 8

Specific coevolution

Diffuse coevolution

Escape and radiate coevolution

Question 9

Specific coevolution

Answer 9

Two species evolve in response to each other e.g. predator prey

Question 10

Diffuse coevolution

Answer 10

Several species involved, their effects are not independent

e.g. genetic variation in host resistance to two different parasite species

Question 11

Escape and radiate coevolution

Answer 11

A prey or host species evolves a major new defense, escapes association with a predator or parasite and diversifies. Later, a different predator or parasite adapts to the host clade and diversifies

Question 12

What is an example of specific coevolution

Answer 12

Heliconius-egg mimicry in Passiflora

Female Heliconius avoids laynig on plants already occupied by eggs as 1st instar larvae are highly cannibalistic

Passiflora plants exploit this by creating fake yellow eggs as deciduous buds, stipule tops or as part of the extrafloral nectaries on young leaves

Example of a plant evolving new defenses beyond the normal chemical ones

Question 13

What is the argument to stay that cheetahs and their prey have reached the limits of the evolutionary arms race?

Answer 13

They cannot get any faster without a negative trade off

For example reducing bone density anymore would make them too weak

Question 14

Coevolution of the rough-skinned newt and the garter snake?

Answer 14

Rough skinned newt are very toxic, toxic enough to kill 100 humans

Garter snake have evolved resistance to the toxins

Arms race becoming more toxic and developing resistance to the toxins

Newt trade of between: Producing less toxin and more likely to be eaten but producing more offspring or vice versa

Snake trade off: Too little toxin resistance unable to eat toxic newts but has a higher crawling speed and vice versa

Question 15

evolution of milkweed and monarch butterfly

Answer 15

Milkweed has produced chemical defenses (latex) and butterflies have evolved immunity

Butterfly resistance caused the larvae to be toxic themselves

Monarch butterfly has evolved Mullerian mimicry to this butterfly to reduce predation

This is not an example of coevolution as it is not recipricol

Question 16

What are the two types of beneficial interactions?

Answer 16

Mutualism and commensalism

Question 17

Mutualism

Answer 17

Both species benefit

Question 18

Commensalism

Answer 18

An interspecific relationship in which one species (commensal) obtains benefits such as food, shelter or locomotion from another species (the host) without causing adverse effects

Question 19

Example of mutualism

Answer 19

Accacia plants and accacia ants

Plants provide accomodation and food bodies

Ants in turn protect plant against vines, herbivores and pathogens

Question 20

Coevolution of flowering plants and pollinators?

Answer 20

Large diversity of floral strategies and pollinator adaptations

The great variety in colour, form and scent we see in flowers is due to the close associations between flowers and pollinators

80% of plants are pollinated by other organisms

Some pollinators pollinate multiple species but other pollinate single species

Orchids are typically pollinated by a single species and are the largest group of plants