Predation and Dispersal Flashcards
What is absolute fitness? (in equations, W)
Expected number of offspring an individual will produce in its lifetime
What does absolute fitness depend on?
Viability e.g. longer life
Reproductive success e.g. gamete production
What is relative fitness? (w in equations)
How does it affect inheritance?
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.
What are the 4 fitness effects?
Effect on each organism?
Mutualism +/+
Competition -/-
Commensalism +/0
Predation +/-
What is physiological crypsis?
Evolution of hiding physiology i.e. features like colouration to avoid predation e.g. the peppered moth
Behavioural crypsis?
Hiding behaviours to avoid detection e.g. Catocala moth rests with its head placed up or down, which is correlated with reduced predation
What is masquerade?
Organisms avoid notice through exploitation of predator sensory limitations - they are still seen
Examples of masquerade? (2)
Cephalopods change colour to mimic surrounding environment
Snowberry flies imitate the aggressive dance of the zebra spider to deter jumping spiders
Masquerade in predators?
Deception e.g. sideways facing eyes, which are indicative of prey
Or pheromones that resemble those of prey
Masquerade in parasitoids?
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
Fitness interactions in the ant/butterfly/wasp system?
Butterfly and ant: predation
Butterfly and wasp: predation
Wasp and ant: commensalism or mutualism
Visual aposematism?
Bright colouration to advertise danger, avoiding predation through learning
Behavioural aposematism?
Stotting in springbuck - leaping as they run from predators indicates they have sufficient energy to escape and the predator is wasting their time
Cost of aposematism? (e.g. Monarch butterflies)
Can be significant e.g. Monarch butterflies absorb a toxin as larvae to give them their toxicity, at the cost of reduced growth rates
Effect of density on aposematism
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
Hypotheses for evolution of aposematism (3)
Foraging neophobia - predators avoid new food sources
Sexual selection
Co-option of colouration
Batesian Mimicry? Fitness effect?
Mimic organism imitates a well defended model e.g. snakes
Predation - mimic gains protection, model loses deterrant
Mullerian Mimicry? Fitness effect?
Both species are dangerous, mimicking and modelling each other
Mutualism
Difference between masquerade and mimicry?
Evolutionary dynamics of model affected by mimicry (i.e. fitness effects)
Why might population size fluctuate rapidly?
Linked to predation populations e.g. growth rates lag behind as prey/predator pops grow
What is Holt’s theory of dispersal?
Predicts that in a temporally constant environment, there will be no dispersal
Carrying capacity and absolute fitness in patches?
Average population size - in places with high K, absolute fitness > 1 - dispersal reduces K and so seems to reduce absolute fitness
Negative costs of dispersal? (4)
Energetic costs
Dispersal physiology
Predation
Failure to find new habitat
Temporally variable environments?
Habitats fluctuate in nature, so patches exist with slightly different qualities - one may empty out to allow dispersal
What favours dispersal?
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
Effect of invasions on dispersal?
Invasion leads to dispersal - new predators encroach on territories
Kin avoidance in dispersal?
Inbreeding is avoided through deleterious alleles which are exposed when recessive ones combine in inbreeding (i.e. aim to avoid this)
Environment in dispersal? moths example
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
Sex in dispersal? (2)
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
Philopatry?
Remaining in patch
