ecological footprint

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Extinctions Extinctions

Theory

Historical Extinctions Contemporary Extinctions

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Extinctions - Theory How long do species survive?

First, what about chronospecies?

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Evolutionary change within a species.

Chronospecies

How long do species survive?

First, what about chronospecies?

Species survival can be misleading if your looking at fossil record.

Species survival can be misleading if your looking at fossil record. So instead ask: How long does a clade survive?

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Taxonomic Categories Clade - any group of related organisms at a level above species.

Dinosaur Clades at the Level of Order

Velociraptor

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Tyrannosaurus How long does a clade survive?

Time

Clade Extinction Rate - Exponential Decay

C ha

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Clade survival Plants 1 to 10 million years

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Clade survival Mammals 0.5 to 5 million years

Extinction Risk Factors

•  Narrow geographic range.

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Golden Lion Tamarin Extinction Risk Factors

•  Narrow geographic range. •  One or few populations.

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Puerto Rican Parrot Extinction Risk Factors

•  Narrow geographic range. •  One or few populations. •  Small population size.

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Kakapo Extinction Risk Factors

•  Narrow geographic range. •  One or few populations. •  Small population size. •  Island Habitat.

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Socotra Dragon Tree Extinction Risk Factors

•  Narrow geographic range. •  One or few populations. •  Small population size. •  Island Habitat. •  Hunting or harvesting by people.

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Rhinoceros Extinction Risk Factors

•  Narrow geographic range. •  One or few populations. •  Small population size. •  Island Habitat. •  Hunting or harvesting by people. •  Chapter 5 in your textbook lists several

other lesser factors. 28

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Theory of Island Biogeography

•  Predicts dynamic equilibrium of species on any particular island based on: – Size of Island.

Montserrat 102 sq km

Jamaica 10,991 sq km

Which one has more species?

Why?

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Island size and biodiversity

•  Larger islands tend to have more types of habitats.

•  Larger islands tend to have a greater amount of area in any given habitat.

•  Larger area of habitat can support larger population.

•  Larger population are less likely to go extinct.

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Time

Population Size and Extinction

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Population Size and Extinction

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Demographic Stochasticity

Time

Population Size and Extinction

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Time

Population Size and Extinction

P op

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Population Size and Extinction

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Population Size and Extinction

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Threshold

Time

Population Size and Extinction

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Population Extinct

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What’s the real world pattern?

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Island size – Caribbean Islands and Number of Animal Species

Exponential Increase

Theory of Island Biogeography

•  Predicts dynamic equilibrium of species on any particular island based on: – Size of Island. – Distance from mainland source of species.

Pacific Islands Decreasing Diversity from Mainland

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Number of species on Island determined by Immigration Rate Extinction Rate

Number of species on Island determined by Immigration Rate : Species Added Extinction Rate : Species Subtracted

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Habitat Fragmentation creates habitat islands that are smaller and more isolated than the larger landscape they came from.

Habitat Fragmentation creates habitat islands that are smaller and more isolated than the larger landscape they came from.

Predict fragmented landscapes will lose species.

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Theory of Island Biogeography

•  Predicts dynamic equilibrium of species on any particular island based on: – Size of Island. – Distance from mainland source of species. – Particular group of organisms.

Theory of Island Biogeography

•  Predicts dynamic equilibrium of species on any particular island based on: – Size of Island. – Distance from mainland source of species. – Particular group of organisms.

•  Method of dispersal (flying, swimming, wind borne, etc.).

•  Position on food web and energy pyramid.

Energy Pyramid

Apex Predator

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Confirmation of Theory Florida Keys Experiment What do theories about

islands have to do with current extinctions?

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Fragmented habitats are like islands. Biological Dynamics of Forest Fragments Project

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MCS or BDFFP

•  Small islands (fragments) decreased faster.

MCS or BDFFP

•  Small islands (fragments) decreased faster.

•  First order create second order.

MCS or BDFFP

•  Small islands (fragments) decreased faster.

•  First order create second order. •  Smaller populations go extinct faster.

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Effective Population Size Effective Population Size

Bottlenecks Genetic Drift Inbreeding Depression

Bottleneck – Founder Effect

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Bottleneck – Founder Effect Bottleneck – Founder Effect

Genetic Drift

By chance, in small populations some genes become more

prevalent or less prevalent. This reduces genetic diversity.

This can result in lower survival

and reproductive output of resulting young.

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Inbreeding Depression

In small population high likelihood of breeding with

genetically similar individuals.

This can result in lower survival and reproductive output of resulting young.

Cheetah

Small population extinction factors

Demographic stochasticity Population Vortex

Small population extinction factors

Demographic stochasticity

Chance variation in number of offspring or sex ratio

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Small population extinction factors

Population Vortex

Inbreeding Depression Genetic Drift