Extinction

The dodo

What makes species vulnerable to extinction?

Passengerpigeon

Passengerpigeon

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

4. limited adaptability and resilience - salmon return to natal stream to reproduce; won’t go elsewhere

Konza Prairie – Kansas

African wild dog

California Condor

Coho salmon

Salmon Life Cycle

Coho Salmon support 137 species

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

ThreatenedAndEndangeredSpecies inIllinois

Four-toed salamander – found at Green Oaks

Minimum Viable Population

• The smallest population for a species which can be expected to survive for a long time

• Many factors effect MVP – the study of those factors is often called Population Viability Analysis – or Population Vulnerability Analysis – or PVA

Factors that make populations vulnerable to extinction

• Environmental fluctuations

• Catastrophes

• Demographic uncertainties

• Genetic problems

• Habitat fragmentation

Environmental Fluctuations

Kirtland’s Warbler

Cheetah

Habitat Fragmentation

• Fragmentation is the transformation of large expanse of habitat into a number of smaller patches of smaller total area isolated from each other by a matrix of habitat unlike the original

Domesday Book – 1085-86

Selection from the Domesday Book

Factors that make populations vulnerable to extinction

• Environmental fluctuations

• Catastrophes

• Demographic uncertainties

• Genetic problems

• Habitat fragmentation

Heath Hen – Extinction Vortex

Minimum Viable Population Size

• Another definition - often defined as 95% probability of 100 year survival, but can also plan for longer survival (500 or 1000 years)

• MVP is usually determined by modeling

Forces which may cause extinction

1) deterministic - something essential is removed (habitat loss) or something lethal is added (pollutant, disease, introduced species) - presumably we can act to minimize these risks

Forces which may cause extinction

2) stochastic (random) - environmental, catastrophic, demographic and genetic - this is what we need to worry about and what is hardest to prevent

• environmental randomness effects resources and conditions and we can't do much about it

• catastrophic randomness - floods, fires, hurricanes, volcanoes - can't really prevent but can spread individuals around to minimize the impact

• demographic - just natural random variation in birth and death rates can lead to extinction

• genetic - lack of genetic variability can lead to problems of inbreeding and poor response to diseases and environmental change

Grizzly Bear and 50/500 Rule

MVP – 50/500 Rule?

English Skylark