Island Biogeography Flashcards
What is island biogeography?
The study of the speices composition and species richness on islands
How is an oceanic island created?
- by the uplift of magma from the seafloor created above hotspots,
Describe how a chain of oceanic islands is formed
- continental drift causes one island formed to move away from the hotspot and then another is formed creating a chain of islands
What is an archipelago?
a group/cluster of islands
What does the species- area relationship describe?
The increase in species richness with increasing sampling area
What types of islands have more species?
larger islands have more species
what is genetic stochasticity?
- unpredictable changes in gene frequencies as a result of processes such as random genetic drift
How is genetic stochasticity caused?
In small populations where inbreeding occurs limiting genetic information which could lead to extinction
What is environmental stochasticity?
-unpredictable changes in the environment e.g. catastrophes or climate change
Name the stochasticities which are problematic for small populations
- genetic (changes in gene frequencies)
- environmental (changes in environment)
- demographic (changes in birth rates)
Name the mechanisms proposed to explain species-area relationship
- are per se
- habitat diversity
- evolutionary dynamics
- random placement
What does it mean for an island to be more isolated?
- more isolated an island, greater amount of evolution and speciation
Name the 2 ways in which the creation of new species can occur?
allopatric and sympatric
Describe allopatric speciation
- geological barrier separates a population
- genetic drift
- random mutations
- one population can undergo new environmental factors
- natural selection
- populations become reproductively isolated
Describe sympatric speciation
Population in new island, some become better adapted and become isolated, no geological barrier involved
What is adaptive radiation?
The process in which organisms diversify rapidly from an ancestral species into a multitude of new forms by allopatric or sympatric speciation
Why are islands hotspots of adaptive radiation?
due to the lack in numbers/variety of species and empty niche space
Define depauperate
lacking in numbers or variety of species.
Describe the effects of isolation on islands formed closest to the mainland?
- dispersal dominated system
- no speciation just constant immigration from mainland
What are the isolation effects on islands furthest away from the mainland?
- species dominated system
- high rates of evolution where you can find high rates of extinction not found anywhere else
Describe the Macarthur and Wilson theory
- proposes that the number of species on an island is in dynamic equilibrium between immigration and extinction
What is the link between immigration rates and the isolation of an island?
The less isolated an island (closer to mainland) the higher immigration rates
What is the link between the size of an island and extinction rates?
The larger the island, the lower the extinction rates
What is the problem with the macarthur and Wilson theory on island biogeography?
- doesn’t consider the dynamics of islands
- islands carrying capacity thus must shift across time
Define the carrying capacity of an island
The maximum number of organisms an island can contain
How does an island’s carrying capacity change throughout time?
> immigration and extinction varies through time which means number of species on an island also varies
Why is island conservation so important?
> recent rise in no. extinctions of islands, mainly human induced
Name 5 causes of species extinctions
- hunting for food by humans
- museum and caged bird trade collecting
- introduced species
- disease, carried by vectors migrating to island
- habitats degradation and loss
6 reasons why oceanic islands are susceptible to anthropogenic threats
- species poverty
- evolution in isolation
- ecological release of exotics
- early colonization by europenas
- small scale of island systems
- cross roads of international trade
What is the matrix?
The land-use surroundings a patch habotat
What was teh SLOSS?
A debate in conservation biology in 1970s-90s deciding if it was better to conserve single large areas or several small areas
Why was it decided that it would be better to conserve several small areas like islands?
- Mcarthur and Wilson stated that smaller areas had higher extinction rates
- also if one small area has an extinction of population, it can recolonised from other populations in other areas
- greater habitat diversity
