Island Biogeography Flashcards
What are the three characteristics that the Equilibrium theory of Island Bio-geography tries to explain
Species- Area Curve The effect of isolation - doesnt have to be an island Species turnover - change of species in an area
What are the conditions for the Equilibrium theory of Island Bio-geography (ETIB)?
Islands must be really isolated Islands have a comparable habitat heterogeneity in space and time Species are residents not visiting Definable source genepool
Under the correct conditions how can the ETIB be described?
Dynamic, asymptotic, stochastic
How does immigration change?
As the number of species in an area increases, the likelihood of an immigrant being novel decreases. Therefore as species number decreases, immigration decreases
Distance from source population- further away = decreased chance of immigration (depends on the species + transport method)
How does the number of extinctions change?
Number of extinctions increases as number of species present increases
- Larger pool of possibile extinction events (probability)
- Increased resource utilisation / more competition
How does immigration and extinction interlink?
Describe the species area curve
Number of species increases with area
- Increased number of habitats and niches
- Larger populations, lower extinction rate
S= cA^z
S= equilbrium number of species
c= constant
A= Area
Z= slope parameter of the curve
How do immigration, extinction and area link?
Isolation of an area –> decreasing immigration
rate of extinction higher on smaller islands (number of niches, competition)
Predicted species richness:
Large + Near > Large + Far = Small + Near > Small + Far
What is species turnover?
How the species composition changes over time depsite relatively costant numbers
Due to differing rates of immigration and extinction - dynamic equilbirium model
How could you experimentally test the ETIB
Mangrove Islands
Insecticide and see how species return
Fewer species on far islands than near islands
Species composition will change
Describe some of the predictions of species turnover
Lower turnover on larger islands (lower extinction)
Lower turnover on distant islands (decreased immigration)
Turnover increases with generations of organisms
Small and Near > Large and Near & Small and Far > Large and Far
- As proven by thistle experiment
What is the rescue effect?
high rates of immigration reduce the probability that the species will be temporarily absent.
Distance to immigrants source affects the likelihood of immigration and extinction (more coming over = decreased chances of extinction)
Describe some non-equilbirium situations
Species richness is not in equilbrium due to historical perturbation –> species number is still increasing or decrasing.
Disturbances changes the carrying capacity of an area
Equilibrium models do not account for speciation events.
What is succession?
Changing of the habitats and niches avaliable over time.
Some species depend on other species to create habitats for them
Mosses and lichens colonise rocks, extract minerals but when they die leave soil –> soil builds up over time –> establishment of different species –> climax community
Strengths of ETIB
Simple model
Clear testable results
