Territoriality Flashcards
(38 cards)
evolutionary game theory
- what is it?
- why do we need it?
application of game theory to interaction-dependent strategy evolution in populations
the costs and benefits of actions depend on behaviour of other individuals in the population
key components of a game-theoretic model
players
= participants in game (2-player of multiple-players)
payoffs
= costs + benefits of actions
actions
= option an animal can choose
decision mechanisms
= single or repeated, simultaneous or sequential
evolutionary stable strategy (ESS)
set of behaviours adopted by all players
that cannot be invaded by any alternative strategy
that is initially rare
Hawk-Dove game
- rules
2 animals meet
- both want access to a resource value V
play Hawk
= attack opponent + may gain full V
BUT has cost of injury, C
play Dove
= don’t fight
Hawk-Dove game
- Payoff matrix
2 doves
= V/2
focal Dove vs Hawk
= 0
focal hawk vs dove
= V
focal hawk vs hawk
= (V/2) - C
if v/2 < C then what’s the best strategy?
frequency dependent:
only doves in population
-> play hawk
only hawks in population
-> play dove
(at least you don’t pay the -ve cost) (0 > -ve)
if V/2 > 2C then what’s the best strategy?
always play hawk
- cannot lose
Hawk-Dove game
- ESS
p that an individual plays Hawk
p* = V/2C
when V/2C
Hawk-Dove game
- cichlid fish example
if asymmetry in fighting ability
-> contest ends in early phases
if individuals matched
-> contest ends in final phase (costs escalate -> dangerous fighting)
Hawk-Dove game
- golden orb weaver spider example
males mate only once + guard against rivals
mated males won contests against virgin males (even if physically inferior) (virgins give up as can find another female)
contests between mated males = high freq of injury
ideal free distribution
Fretwell 1972
- 2 rules
> every individual is free to choose where to go
> no limit to no. of competitors
ideal free distribution
- predicted pattern
1st arrivals go to rich habitat
more competitors lower the rewards per individual by resource depletion
at a point poor habitat will be equally attractive
SO the 2 habitats should be filled so that the rewards per individual are the same in each
ideal free distribution
- sticklebacks
add 2x as much food to side B of tank
still had 2 fish left at side A
(not 0)
-> although those at B may be getting 2x as much food.. they’re competing with 2x fish
no. of fish is in proportion to the amount of resources available
what is the main point of ideal free distribution?
all about individual choice in a population in terms of distribution
resource use by waders
- 2 predictions for distribution
surface distribution model
= equal densities over total surface
- only depends on amount of individual space
ideal free distribution model
- depends on space and richness for feeding
resource use by waders (Red knots)
- conclusion if resources are fixed
ideal free distribution model
resource use by waders
- why aren’t resources fixed over time?
depletion by predators
reproduction of prey
emigration and immigration of prey to + from different patches
resource use by waders
- experiment
- results
exclude waders from some patches
-> after 13 days compare prey densities between excluded + control sites
inside enclosure
- prey densities increased
outside
- densities decreased
resource use by waders
- what does the experiment show?
if you force individuals to not distribute themselves
-> it will effect the prey
predators modify their own environment in a way that affects resource availability
dispersal
- natal
- adult
- what happens after the dispersal stage?
young animals leave home
adults change sites to find better feeding location, mate or breeding territory
animals often stay in/return to the same location for rest of life
dispersal
- why disperse?
- cost
- benefit
- costs + benefits are often…? which leads to..?
> forced to
benefits of dispersing exceed its cost
mortality
outbreeding
sex-specific
-> sex difference in dispersal propensity
dispersal influences population structure via?
emigration
immigration
what are meta-populations?
group of populations separated by space but consist of the same species
made up of sources and sinks
drives connectedness
- more related populations in if they have more movement between
conservation importance using meta-populations
suitable habitats are rapidly fragmenting globally
efforts should focus on sources
- can supply multiply sinks and doesn’t depend on another population for individuals
