BIOL 2251 Study Guide - Final Guide: Background Extinction Rate, Species Richness, Biodiversity Hotspot

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26 Aug 2017
School
Course
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BIOL 2251
Final Review
Chapter 13 - Island Biogeography: Patterns in Species Richness
Why are islands ideal subjects for natural experiments? Why do we study them?
o They
Are microcosms
Have defined boundaries
Are various sizes
Have varying degrees of isolation
Have a known set of endemic species
Are easily controlled
React noticeably to anthropogenic factors
o Can apply information to bigger landmasses
How much land surface is considered insular??
o 5%
o High biodiversity
Species richness is higher on (1) bigger islands and (2) islands that have a closer
proximity to the source
Realizations due to Insular Observations
o Evolution of species by means of natural selection
o Allopatric speciation
o Character displacement
o Other kinds of islands:
Mountains
Desert oasis
Wetland
Urban Greenspace
Can use these spaces to increase biodiversity
Urban greenspace Parking lot City Parks Conservation
Areas (LLELA)
o Want large conservation areas rather than small because
of edge effect (discussed in ch.16)
Playa Lake
MACARTHUR and WILSON
o MACARTHUR
Student of Hutchinson
Doctoral dissertation, Yale (1958) on competition and coexistence of
warblers
o WILSON
Strongly influenced by Mayr
Worked on the origin and relationships of ants on island in the East Indies
and South Pacific
Who is the father of biodiversity?
Wilson
o Equilibrium Theory of Island Biogeography (ETIB) - 1967
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BIOL 2251
Final Review
No longer thought species richness to be static, but dynamic
Platform for current research
Limited niche space: 1 new species 1 goes extinct
o Species richness is higher on (1) bigger islands and (2) islands that have a closer
proximity to the source
As island area , richness
As isolation , richness
Immigration
o Functions based upon the distance the island is from the mainland (the source
population)
Mainland = source population
Island = sink population
SOURCE: Immigration (IN) < Emigration (OUT)
SINK: Immigration (IN) > Emigration (OUT)
Immigration decreases with isolation
Difficulty in dispersal
Only a select group may arrive at a distant island
Things that can colonize sinks (islands):
Aerial adult insects
Birds
Fish
o Ex: How do they get in fresh water ponds?
Birds carry them
Plants
Phoresy
Endo/Exozoochory
Successful colonization decreases with species richness, due to increased
competition
EX: Same size islands, same distance from the source
Extinction
o Function of island area
Smaller islands have higher extinction rates
Provide fewer resources
30
SPECIES
10
SPECIES
- niche availability
- space
- competition
- niche availability
- space
- chance of successful colonization
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BIOL 2251
Final Review
Lower habitat heterogeneity
Support fewer individuals within a species, which makes species
more vulnerable to extinction
o The biggest decrease in species on islands is due to invasive species
Three things that go into the Equilibrium Theory of Island Biogeography (ETIB)
o Species-area relationship
ARRHENIUS Equation (Power Model)
S = cAz
S = species richness
o Richness = # of species in a given area
c = fitted constant
o Varies considerably for different taxa and habitat types
o Need to do research to find the past value for c and tweak
it
A = island area
z = slope of the relationship between S and A on the log scale
o Relatively stable and usually a value of 0.15 0.35
The relationship of the number of species (richness) and area of land is
NOT linear; however, you can alter c and z to make it linear but it is not
found in nature that way.
As you get to a certain land size, species # slows dramatically,
levels out, and appears to no longer increase
Canonical log-normal distribution in the numbers of individuals among
species
- Few species
- abundances
- Rare
- Most species
-n 100
- Few species
- abundances
- Can be the majority of the
biomass in a given area
- Common
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