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

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

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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

The dodo What makes 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 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