Lecture 10 Dispersal, metapopulations, and island biogeography Flashcards
are real populations close systems (settings that cannot transfer energy to their surroundings)
no
dispersal definiton
individuals moving from one population to another
What does Dispersal allow organisms to do? CEI
Colonize new areas
Escape competition
Avoid inbreeding depression (reduced survival and fertility of closely related individuals)
what helps taxas disperse
evolving traits that aid in dispersal
why is dispersal important? (4) CRIC
for colonization of new habitats
range shifts due to climate change
islands
connecting populations
metapopulation
group of spacially separated populations of the same species which interact at some level
patch
spatially distinct population
what can metapopulation structure allow? significance?
population persistence even when individual populations are doomed
Local populations can be renewed by colonists from other populations after going extinct
what are the sinks and sources in source-sink dynamics?
sinks; populations in small habitat
patches that would go extinct
source; Migrants from ‘source’ populations ‘rescue’
these populations
what are the prey and predator populations like when some prey colonize an empty island?
prey population low
predator population zero
what are the prey and predator populations like when prey quickly grows toward carrying capacity?
more prey no predators
what are the prey and predator populations like when Some predators arrive and reproduce rapidly?
large prey population small predator population
what are the prey and predator populations like when predators drive prey to extinction?
predators population medium
prey population zero
what are the prey and predator populations like when predators starve, the island is empty?
prey population zero
predator population zero
patch dynamics similar to
population dynamics
what to do to find patch dynamics
we track patch occupancy through time
when do Populations within patches go extinct?
at some constant e
what is the colonization of patches affected by? (4) ONER
number of currently occupied patches
the number of patches, the more patches the more colonizers
The fraction of empty patches
rate patches are getting filled up, as patches fill up, fewer patches to colonize
colonization rate equation
cP(1-P)
Levins patch occupancy model
dP//dt=cP(1-P)-eP
at equilibrium what does Levin patch occupancy model equal?
zero
why is local coexistence is impossible?
Say A always outcompetes B within a habitat patch
what does global coexistence require? (3) ECDC
A must sometimes go extinct in a patch OR new patches must be created from time to time
B must be a better disperser than A
so B must be a “fugitive”, “tramp” ,” weedy”, opportunistic”, and “transient” species
A competition-colonization trade-off
what are the ways a population can be driven to extinction? SCIA
Stochasticity
Competitive exclusion
through predator-prey interactions
allee effect(positive relationship between fitness and population density) at low-density
Stochasticity
chance fluctuations in population numbers
what stops populations from being driven to extinction (2)
Predation keeping competitive exclusion from going to completion
Non-equilibrial conditions, habitat patchiness, rescue-by-migration, variation in life-history strategy (competition colonization tradeoff)
metacommunity
set of local communities that are linked by dispersal
what determines the number of
species on an island? definitions of each? CEI
colonization: a species can arrive on an island from elsewhere
extinction: a species can go locally extinct on an island
In-situ speciation: a lineage can split in two on an island, but this is a very slow process
what was MacArthur and Wilson’s theory of island biogeography? when is this theory ignored?
predict the number of species on an island from the island’s size and isolation (distance from mainland)
Ignored in-situ speciation;
only considered colonization and extinction to determine population size
