bio120 FINAL

dispersal allows organisms to

• colonize new areas

• escape competition

• avoid inbreeding depression

diversity in canada after glacial period is largely from:

dispersal

metapopulation

collection of spatially distinct populations connected via dispersal

if there is dispersal, a locally unstable system can be…

globally stable

P

number of occupied patches

1-P

number of empty patches

formula for patch colonization rate

cP(1 - P)

constant e in patch model

chance that a patch goes extinct / from occupied to unoccupied

Levin’s patch occupancy model

Levin’s patch occupancy model AT EQUILIBRIUM

if a is a better competitor than b and they wanna globally coexist then…

b has to be a better disperser

populations can go to extinction through

• stochasticity

• competitive exclusion

• predator prey

• allee effects

extinction effects countered by

• predation preventing total competitive exclusion (Paine’s sea stars)

• non equilibrial conditions, habitat patchiness, rescue by migration, variation in life history strategy

metacommunity

communities linked by dispersal

theory of island biogeography

lotka volterra equation for mutualism

what limits population growth of mutualists?

• intraspecific competition

• third species e.g. predator

• diminishing returns as population grows

invasional meltdown

two non-native species facilitate each other’s spread

survivorship curves examples (I, II, III)

human, bird, bug

geometrical growth model + 𝜆 meaning

• 𝜆 = net reproductive rate = (per capita birth rate - per capita death rate)

exponential growth model + r meaning

r = net growth rate

logistic model of density dependence

logistic model + allee effect + A meaning

A = allee threshold

equation for R₀

equation for T / generation time + what it means

average age at which a female gives birth

4 possible outcomes of competition

1. Species 1 outcompetes Species 2

2. Species 2 outcompetes Species 1

3. Two species stably coexists, both remaining under K

4. Competition is unstable, winner depends on starting numbers

𝜆 vs r vs R₀

fecundity

number of offspring an individual has

l_x

probability of being alive at age x

m_x

# daughters born to female of age x between x and x+1

iteroparity

potentially reproduce numerous times

semelparity

reproduce once and then die

v_x

expected # of daughters to be produced by a female of age x, now and for the rest of her lifetime

scramble competition

depletion of shared resource

contest/interference competition

direct interactions e.g. battles over territory)

lokta volterra model

alpha meaning lokta volterra

competition coefficient - per capita effect on one species by the other
e.g. one squirrel is equivalent to 4 sparrows

coexistence requires intraspecific competition __ interspecific competition

>

stability

ignore

stability

ability of system to return to equilibrium following disturbance

principle of competitive exclusion

if two species have same niche one will outcompete the other into extinction

resolving paradox of plankton

• lv model to simple

• real conditions fluctuate

• environmental factors

lv for predator prey predicts

coupled, lagged population cycles

why are predator prey cycles rare irl

• they have other prey

• hares might be cycling w/ their food

antagonistic coeevolution

arms race —> prey evolves defenses and predators evolve to overcome them

red queen hypothesis (coevolution)

both predator and prey are evolving as fast as they can but that lowkey means they remain in the same place

life dinner principle

predicts prey are under stronger selection to make defenses than predators are to overcome them (life vs. dinner)

enemy release hypothesis

invaders’ impacts results from having fewer natural enemies in their new range

dilution effect

host diversity can dilute disease risk to humans or animals

amplication effect

more host / vector species can support larger populations of disease causing organisms