Lecture 22: Biodiversity & Global Ecology: Biodiversity equilibrium Flashcards
________________ can be seen as ____________________ from the balancing of mechanistic factors that ______________________ from a location.
- Biodiversity
- equilibrium reached
- add and subtract species
4 broad factors that add and subtract species
- Speciation rate
- Extinction rate
- Colonization
- Local extinction
4 broad factors that add and subtract species - speciation rate
ultimate source of diversity
4 broad factors that add and subtract species - extinction rate
ultimate loss of species
4 broad factors that add and subtract species - colonization and local extinction
determined by local interactions
Speciation is the ultimate source of biodiversity, but _______________________________
requires larger areas and long timescales
The biodiversity of ___________, like islands, is ____________________________________ and ______________________________________
- small areas
- limited to additions from colonization
- loss from subsequent local extinctions
_________ are useful for limiting biodiversity studies to the processes of _______________________
- Islands
- colonization and local extinction
The____________________________________________________ by Robert MacArthur and E. O. Wilson – the number of species on an island balances processes of colonization and local extinction
equilibrium theory of island biogeography
_________________ for new species _____________, as the island _______
- Colonization rate
- declines over time
- fills up
ultimate limits to colonization
when all regional species are on the island, colonization must be zero
_________________ of species drives _____________________________ – more species means more likelihood of local extinction due to local interactions
- Accumulation
- increasing rate of local extinction
Balance of colonization and extinction on islands
Where the decreasing colonization rate and the increasing extinction rate cross is the equilibrium state for biodiversity on the island
Why does the rate of colonization decelerate to zero as island diversity increases?
If an island is adding species through time, at some point if that island has every single species, the colonization rate must be zero
Why does the rate of local extinction accelerate as island diversity increases?
It gets more and more hostile as more species are present
Balance of colonization and extinction on smaller islands
- Smaller islands increase the likelihood of chance extinctions, and amplify the negative effects of more species arriving on the island
- lower equilibrium biodiversity
Balance of colonization and extinction on closer islands
- Chances of colonization decrease with increasing distance from sources of colonizing species – reduced “species rain”
- Equilibrium biodiversity is higher
Simberloff and Wilson’s classic test in the Florida keys
- Islands that are further away colonize at a slower rate and level off at a lower equilibrium biodiversity.
- All islands return to close to original biodiversity.
The ___________________ of biodiversity also applies to _________________
- equilibrium view
- continental landmasses
____________________ are _____________________________ on continents
- Speciation and extinction
- extra sources of additions and subtractions
Large islands or any location on continents have _____________________________________________
higher species richness than expected by colonization alone
The ______________ richness comes from the __________________________________________ — endemic speciation and extinction rate.
- extra species
- net balance of speciation rate and extinction rate
The balance of speciation and extinction
- Speciation rate starts very low and accelerates then plateaus
- Extinction rate accelerates through time
- Equilibrium point is at the top where the extinction and speciation rate meet - species “rain”
Why does speciation rate decelerate and plateau?
- It starts very low when there is no species bc you need species to produce more species
- It declines bc landmass becomes filled up and there is no space for it to diversify
