Predation and Dispersal

Question 1

What is absolute fitness? (in equations, W)

Answer 1

Expected number of offspring an individual will produce in its lifetime

Question 2

What does absolute fitness depend on?

Answer 2

Viability e.g. longer life

Reproductive success e.g. gamete production

Question 3

What is relative fitness? (w in equations)

How does it affect inheritance?

Answer 3

Absolute fitness/average fitness of a population

If an individual produces more offspring than the pop. mean, w >1 and the phenotype increases in the next generation.

Question 4

What are the 4 fitness effects?

Effect on each organism?

Answer 4

Mutualism +/+
Competition -/-
Commensalism +/0
Predation +/-

Question 5

What is physiological crypsis?

Answer 5

Evolution of hiding physiology i.e. features like colouration to avoid predation e.g. the peppered moth

Question 6

Behavioural crypsis?

Answer 6

Hiding behaviours to avoid detection e.g. Catocala moth rests with its head placed up or down, which is correlated with reduced predation

Question 7

What is masquerade?

Answer 7

Organisms avoid notice through exploitation of predator sensory limitations - they are still seen

Question 8

Examples of masquerade? (2)

Answer 8

Cephalopods change colour to mimic surrounding environment

Snowberry flies imitate the aggressive dance of the zebra spider to deter jumping spiders

Question 9

Masquerade in predators?

Answer 9

Deception e.g. sideways facing eyes, which are indicative of prey
Or pheromones that resemble those of prey

Question 10

Masquerade in parasitoids?

Answer 10

Phengaris rebeli (butterfly) that imitates ants to lay eggs within the colony and exploit their feeding.

A second predator, a wasp, secretes pheromones to enter the colony and lay eggs on the butterfly larvae, which consume it as they grow

Question 11

Fitness interactions in the ant/butterfly/wasp system?

Answer 11

Butterfly and ant: predation
Butterfly and wasp: predation
Wasp and ant: commensalism or mutualism

Question 12

Visual aposematism?

Answer 12

Bright colouration to advertise danger, avoiding predation through learning

Question 13

Behavioural aposematism?

Answer 13

Stotting in springbuck - leaping as they run from predators indicates they have sufficient energy to escape and the predator is wasting their time

Question 14

Cost of aposematism? (e.g. Monarch butterflies)

Answer 14

Can be significant e.g. Monarch butterflies absorb a toxin as larvae to give them their toxicity, at the cost of reduced growth rates

Question 15

Effect of density on aposematism

Answer 15

High density populations mean predators will encounter many prey and learn quickly to avoid them
Low density = learning not as common and so aposematism is maladaptive - crypsis more useful to avoid detection

Question 16

Hypotheses for evolution of aposematism (3)

Answer 16

Foraging neophobia - predators avoid new food sources
Sexual selection
Co-option of colouration

Question 17

Batesian Mimicry? Fitness effect?

Answer 17

Mimic organism imitates a well defended model e.g. snakes

Predation - mimic gains protection, model loses deterrant

Question 18

Mullerian Mimicry? Fitness effect?

Answer 18

Both species are dangerous, mimicking and modelling each other
Mutualism

Question 19

Difference between masquerade and mimicry?

Answer 19

Evolutionary dynamics of model affected by mimicry (i.e. fitness effects)

Question 20

Why might population size fluctuate rapidly?

Answer 20

Linked to predation populations e.g. growth rates lag behind as prey/predator pops grow

Question 21

What is Holt’s theory of dispersal?

Answer 21

Predicts that in a temporally constant environment, there will be no dispersal

Question 22

Carrying capacity and absolute fitness in patches?

Answer 22

Average population size - in places with high K, absolute fitness > 1 - dispersal reduces K and so seems to reduce absolute fitness

Question 23

Negative costs of dispersal? (4)

Answer 23

Energetic costs
Dispersal physiology
Predation
Failure to find new habitat

Question 24

Temporally variable environments?

Answer 24

Habitats fluctuate in nature, so patches exist with slightly different qualities - one may empty out to allow dispersal

Question 25

What favours dispersal?

Answer 25

Youth
Isolation of patch i.e. if it’s empty
Connectivity - isolated populations on their own are more dispersive than if surrounded by filled patches

Question 26

Effect of invasions on dispersal?

Answer 26

Invasion leads to dispersal - new predators encroach on territories

Question 27

Kin avoidance in dispersal?

Answer 27

Inbreeding is avoided through deleterious alleles which are exposed when recessive ones combine in inbreeding (i.e. aim to avoid this)

Question 28

Environment in dispersal? moths example

Answer 28

Bad environments encourage dispersal e.g. the cannibalism of moths living on corn when food is scarce.
Cannibalistic larvae are smaller but have the same size wings and so have better dispersal mechanisms

Question 29

Sex in dispersal? (2)

Answer 29

Resource dependence; mammals often have females remaining because they raise children
Male birds often better at guarding and child rearing so they remain

Sexual selection - female choice means moving gives greater choice
Males get greater pool

Question 30

Philopatry?

Answer 30

Remaining in patch