Biogeography Flashcards
What is biogeography?
This is the study of patterns of species composition and diversity across space and time
What can maps show?
Species ranges
How can patchiness be explained?
Organisms have physiological tolerances and are also influenced by biotic interactions
How can species ranges vary?
Through space and time
Why can one species increase and another decline?
Competition for resources
What are physiological tolerances?
Tolerances for certain abiotic factors
How can history explain patchiness?
Distribution related to contingent events in the past such as chance dispersal and evolution
Why are there more grey squirrels than red squirrels?
Grey ones carry a pathogen that they are resistant to but red squirrels aren’t
Why is biogeography important?
Species composition influences ecosystem function
We need to understand the response of organisms to environmental change
What do biogeographers look for?
Patterns in the biosphere and underlying casual mechanisms
How are floral and faunal realms categorized?
They are now separately defined
What is Wallace’s line?
A recognised boundary between biogeographic provences
Why can there be a blurred line?
Because of species identity
What is Weber’s line?
This is the boundary of faunal balance
What is a good example of chance dispersion?
Islands
What can cause spatial variation?
Competition
Define biomes?
Large-scale ecological units distinguished by similar biological communities and climates
What do biomes act as?
Arbitrary boundaries
What is similar and different in biomes?
Species identities are not the same but vegetation types are
Where is the highest species richness?
In equatorial regions
What is the trend for diversity?
It declines with increasing latitude
Why is there regional variation?
This is because of altitudinal gradients
Ecotones between vegetation types
Elevations vary with latitude and aspect
What can lead to less biodiversity?
Aridity
Why does biodiversity decline at higher latitudes?
Because temperatures decline
How can plants adapt to aridity?
By having extensive root systems
Why can there be small-scale patterns?
Landscape-scale variation
Micro-environmental factors
Ecological processes
Anthropogenic disturbance
Give an example of an ecological process?
Competitive exclusion
What is an issue with plants having extensive root systems?
They draw moisture away from a larger area and there is no biodiversity in these areas with no moisture
Which level of diversity has the smallest spatial scale?
Alpha
Which level of diversity has the most diversity?
Alpha
What are 4 temporal scales?
Geological
Evolutionary
Long-term ecological
Short-term ecological
Give an example of an influence in a geological timescale
Plate tectonics
Give an example of an influence in an evolutionary time scale
Speciation
Give an example of an influence in a long-term ecological time scale
Succession
Give an example of an influence in a short-term ecological time scale
Seasonal changes
Species interactions
What is the biome approach not driven by?
Taxonomy
Where can similar types of vegetation be found?
In areas with certain types of climate
Why is temporal scale important?
Ecosystems vary across a range of timescales
The most relevant process depends upon the scale of reference
Give an example of a range shift
Migration
What can occur as a result of seasonal change?
Changes in biomass/ relative abundance
Range shifts
What type of organisms have faster evolutionary changes?
Organisms that have more offspring quickly will have faster evolutionary changes than those that reproduce slower
What do seasons have an impact on?
Growth
How long does succession occur?
Decadal-centennial change
What are the 6 stages of succession?
Nudation Migration Ecesis Competition Reaction Stabilisation
Briefly explain succession
Facilitation-based
Holistic: community has clear developmental stages
Convergence towards the climatic climax
Explain primary succession
Succession on terrain with no biological legacy
Natural and anthropogenic substrates
Predictable changes in key parameters
Explain what happens at glacier bays
Primary succession on glacial forelands
Predictable changes in species composition and soil propoerties
Explain secondary succession
Some organisms persist post-disturbance
Reforestation
Qualitatively different from primary succession
What is another term for lakes?
Hydrsere
Explain lake succession
Changes in vegetation type as lake is infilled
Allogenic succession
What is meant by allogenic succession?
It is driven by abiotic compoments
When did the quaternary begin?
2.6 Ma
What are some changes that occurred in the quaternary?
Expansion/ contraction of ranges to track climate
Fluctuations in population size, as well as distribution
What happened during glacial periods?
Temperate taxa ride out glacial periods in refugia
What is refugia?
This is an area in which a population can survive in unfavourable conditions
What happened post-glacial period?
Expansion
Explain post glacial colonisation of the UK
Broad leaf species replace pioneer colonists and herbs
What record provides evidence of post glaciation?
Pollen record
Who are two founders of evolutionary theory?
Darwin and Wallace
When do populations stop expanding?
When there is limited resources
What does the number of descendants partly rely on?
Interactions between the characteristics of individuals and the environment (fitness)
What can explain similarities in widely-separated locations?
Continental drifting
Explain the link between the ratites and tectonics
Contemporary species descended from a common Gondwanan ancestor
What is the equilibrium model of island biogeography?
Seminal work of ecological theory
Revolutionary in terms of mathematical treatment
Highly influential in conservation biology
What is nudation?
A disturbance
How predictable are primary processions?
Relatively predictable
What is the empirical basis for the theory of island biogeography?
Species richness appears to be correlated with:
- island area (big islands have more species)
- distance from source area (remote islands have fewer species)
What are the essential features of the island biogeography model?
Species richness determined by:
1- rate of immigration of new species
2- rate of extinction of existing species
What does the theory of island biogeography say about the impact of size and distance to mainland?
Big, close islands have high equilibrium diversity
Small, far islands have low equilibrium diversity
What are 3 advantages of the island biogeography theory?
Provides a general explanatory framework
Island habitats come in many forms
Same principle; predictive
What are the 3 weaknesses of the theory of island biogeography?
No evolutionary/ historical dimension
Does not explicitly acknowledge habitat diversity
Single metric of diversity (richness)
What happens as glaciers move?
More terrain is uncovered which can then be colonised
What can large scale temperature variation lead to?
Species changes and sea level rise
What does the quaternary record show?
How organisms responded to large scale climate change
Why can species be forced south?
Because of glaciers and ice sheets (refugia)
What can climatic change cause?
An abrupt transition in species
What does the rate of immigration and extinction depend upon?
The species present
What happens to the rate of immigration as the island fills up?
It decreases
What happens to the rate of extinction as the island fills up?
It increases
