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
Interactions that mechanistically influence both species production and extinction through time (net species accumulation), and local colonization and local extinction rates
- Structural complexity
- Solar energy and precipitation
- Biotic mechanisms
influencing biodiversity interactions - structural complexity
- Biodiversity increases with structural complexity/heterogeneity
- Structural complexity is typically more important than productivity for producing and supporting high biodiversity
Why is structural complexity good for producing more species?
Structural complexity provides more niche spaces for different kinds of species to evolve and coexist.
influencing biodiversity interactions - solar energy and precipitation
- Solar inputs matters that most in regions with strong solar gradients – moving through temperate zones towards the poles
- Precipitation matters the most in regions with relatively uniform solar inputs – the tropics
influencing biodiversity interactions - biotic mechanisms
- niche specialization
- Disturbance dynamics
- Consumers and pathogens
biotic mechanisms on species accumulating and sorting - niche specialization
Heterogeneity interacts with niche specialization and the process of competition to facilitate an increase in biodiversity.
biotic mechanisms on species accumulating and sorting - disturbance dynamics
Disturbance dynamics drive environmental heterogeneity and species turnover through time.
biotic mechanisms on species accumulating and sorting - Consumers and pathogens
Consumers and pathogens have greater impact on common species than on rare species, creating turnover of species through time.
Biotic mechanisms: environmental heterogeneity and niche specialization
Competition and specialization may result in tighter packing into overall niche space, further increasing biodiversity
Intermediate disturbance hypothesis
Inhabitable heterogeneity is greatest at intermediate rates of disturbance
Biotic mechanisms: Consumer and pathogen impact and species abundance
Common species may be eaten more, while rarer species escape detection — A possible outcome of consumption by a keystone species.
One army ant species also consistently reduces the abundance of the __________________ non-ant leaf litter arthropods.
most common
Another army ant species ___________ arthropod abundance in _________________
- only reduces
- high-abundance areas
Local diversity = regional diversity
- Theoretical relationship that would pertain if all species within a region were found in all communities
Proportional sampling
- If species are added to a community independently of its existing species richness
- Then the local community should sample the regional species pool proportionally
local ecological saturation
- if local interactions among species limit membership in a community
- then the number of species in the community should level off at an upper limit, or saturation point, above which regional diversity has no effect
define Convergent evolution
- Distantly related species evolve a functional resemblance to each other in response to similar environments.
- Convergence in composition of whole animal communities is also common
Convergent evolution has played a major role in shaping dominant vegetation in types of __________
biomes
________________ in species accumulation and ecological function is also seen in the ___________________________________
- Convergence
- biodiversity of large islands
If _____________________ to allow species production, they act as _________________ from the perspective of biodiversity accumulation.
- islands are big enough
- mini continents
Often see repeated evolution of the same ___________ on different islands
“ecotypes”
define ecotype
a distinct phenotype with a well-defined ecological function
Equilibrium biodiversity production is ____________ when conditions are ______________ — convergent evolution of species phenotype, ecology, and composition of whole communities
- repeatable
- similar
