Transcript Continue Extinction and Island Biogeography

Island Biogeography
MacArthur and Wilson concluded:
1. Small islands have fewer species because
equilibrium species number is set at a
lower level by the balance of immigration
and extinction – this is a dynamic
equilibrium
2. Small islands are more isolated so that
after extinction, the rate of replenishment
is lower for them
Krakatau – before and after 1883 eruption
Aerial photo of Anak Krakatau
and Krakatau
Krakatau today
Mangrove islands off the Florida coast
Mangrove Island Close-Up
Dan Simberloff on Mandolin
Nick Gotelli on Guitar
Simberloff’s defaunation experiment
on Mangroves
Simberloff’s defaunation
experiment on Mangroves
Results from Simberloff’s
Experiment
Results from Simberloff’s
Experiment pt. 2
Island Effect
Why are there fewer species on islands than
on equal sized areas of mainland?
• Differences purely to area?
• Differences due to mainland having more
complex habitat?
Bracken Fern
Bracken Fern - Australia
Number of species found on Bracken Fern
Speciation on Islands
Honeyeaters
Picture Winged Drosophila
Picture Winged Drosophila –
more than 500 species from 1 ancestor
Picture Winged Drosophila –
more than 500 species from 1 ancestor
• http://www.youtube.com/watch?v=xr_YhATOYA&list=PL6C606070246F1C81
&index=6
Cichlid Diversity
African Rift Lakes
Cichlids from Lake Tanganyika
(left) and Lake Malawi (right)
Age of African Rift Lakes
• Lake Tanganyika – 12 million years old;
about 250 species of cichlids; 80% endemic
• Lake Malawi – 5 million years old; about
700 species of cichlids; again 80% endemic
• Lake Victoria – 250,000 to 750,000 years
old; about 400 species of cichlids – over
80% endemic
What makes species vulnerable to
extinction?
The dodo
What makes some populations or
species vulnerable to extinction?
What makes some populations or
species vulnerable to extinction?
• Rare species are more vulnerable to
extinction
• Remember Rabinowitz – three factors
determine rarity:
1. Geographic range
2. Width of habitat use
3. Local population size
Passenger
pigeon
Passenger
pigeon
Allee Effect
• Some species have a minimum requirement
for population size in order to successfully
breed
Characteristics that predispose
species to becoming extinct
1. habitat overlap - the species occupy habitat that is
desirable to humans and lose out in competition with
humans for the habitat - tallgrass prairie species
2. human attention - species suffer because singled out by
humans - either desired as food or fur and hunted heavily
(passenger pigeon, dodo, northern elephant seal); or
disliked by humans and killed as varmints (wolves,
African wild dogs)
3. large home range requirements - animals needing large
areas can’t find large enough areas in human dominated
landscape - California condor, polar bear
4. limited adaptability and resilience - salmon return to
natal stream to reproduce; won’t go elsewhere
Habitat overlap – Konza Prairie, Kansas
Human attention – African wild dog
Large Home Range Requirements California Condor
Limited adaptability and
resilience - Coho salmon
Salmon Life Cycle
Coho Salmon support 137 species
Additional factors
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Species in which population size is declining
Animal species with large bodies
Species that are not effective dispersers
Seasonal migrants
Species with little genetic variability
Species with specialized niche requirements
Species usually found in stable, pristine environments
Species that form permanent or temporary aggregations
Species that have not had previous contact with people
Species closely related to other species that have gone
extinct or that are endangered
Species in population decline –
barn owls
Species with large home ranges –
Polar bear
Animals with large bodies
Species that are not effective dispersers
- Freshwater Mussels
Seasonal migrants such as
Blackpoll Warbler
Species with little genetic variability
– Madagascar fish eagle
Species with specialized niche requirements
– hummingbird flower mites
Species usually found in stable,
pristine environments
Species that form permanent or
temporary aggregations
Species with little or no prior
contact with people –
Western Australia flora
Species related to other extinct or
endangered species - Cranes
Worldwide Endangered Species
Endangered tree species worldwide
Rare and Endangered Species in Japan
Endangered species in Canada
and the US – as of 1990’s
Threatened and Endangered Species
Threatened
And
Endangered
Species in
Illinois
Four-toed salamander – found at
Green Oaks