Lecture 1 Islands Flashcards
(24 cards)
Why are islands useful for studies?
Sharply-defined boundaries - possible to delimit a system for study
Typically have fewer species than mainlands - ease of study
Provide replicated natural communities - natural experiments in assembly
What are community assemblages?
the processes that shape the identity and abundance of species within ecological communities
communities assemble over time by processes such as speciation (evolution) and immigration (dispersal). Local communities are within a regional species pool. e.g. atoll within the whole coral triangle. but sometimes not: island community next to source pool.
Dynamic Equilibrium
dynamic equilibrium between colonisation and extinction, the theory predicts that large islands (or those close to continents) have more species than small islands (or remote islands).
Source Pool
Local species source, land mass
The shorter the dispersal range
higher chance of immigration
the longer the dispersal range
the higher effect of speciation, speciation may overtake immigration.
Equilibrium theory of island biogeography
McArthur & Wilson’s (1967)
In McArthur & Wilson’s (1967) Equilibrium theory of island biogeography, what is immigration?
Immigration is a curve since rate falls off as good dispersers (Tramps and Supertramps [Diamond, 1975]) reach island first, leaving only slower dispersers in source pool
In McArthur & Wilson’s (1967) Equilibrium theory of island biogeography what is extinction?
Extinction is curved due to increased interspecific interactions with increase in species present
more competition more extinction
Predictions of the McArthur & Wilson’s (1967) Equilibrium theory of island biogeography
No. of species roughly constant through time
No. of species is a result of turnover of species through immigration and extinction - dynamic equilibrium
this is the key unique prediction of the theory
Large islands have more species than small (as a larger target won’t necessarily have more niches) species - area relationship
But sometimes species no. declines with remoteness
isolation and dispersal limitation
What else could be an island?
ponds, lakes, mountains, seamounts, reefs, habitat patches etc.
Factors such as area and isolation will therefore be important in shaping the composition of communities
What is a Tepui?
Venezuelan table mountain tops in Brazil
1km vertical drop from top ‘table’ to surrounding lowlands. Completely different communities & some endemic to the table top.
Dynamic equilibrium model
s (species) = M (immigration) + G (speciation) - D (extinction)
Situ Radiation
Island Speciation
What is a propague
The minimal unit of individuals a species requires to colonise and island, 1 mated female, a male and female, whole social structure?
The equilibrium model (EMIB)
The number of species on an island in a dynamic equilibrium between colonisation and extinction. Dependent on island isolation and area. Only this model predicts species turnover
Habitat diversity of islands
Number of species maybe a function effected by number of habitats, larger islands have larger number of habitats
What are Incidence Functions
Some species require larger territories, only possible on larger islands
Species-energy effect
Some islands may have more available resources and therefore greater capacity for richness. Primary resources times area. Not an indication of turnover. (Wright 1983)
Small Island Theory
Some species cannot occur on islands below a certain size. (Whitehead and Jones, 1969)
SmalI island Habitat effect
Some small islands might have habitats not possible on larger islands. Alternatively, may have more habitats than perceived due to altitude.
Disturbance Hypothesis
Small Island undergo greater disturbance and therefor may have greater species loss (McGuinnes 1984) opposite may be true due to disturbance allowing new colonisations.
what is a community?
a group of species populations that occur in the same space and time.
why can island biogeography assist in the building of nature reserves? what quesitons can this assist with?
nature reserves are a lot like island communities in a sea of urbanisation:
How large must a reserve be to maintain a given diversity of species?
How close should individual reserves be to each other in a network?
Is one large reserve better than several small ones (SLOSS)?
