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EXTINCTION EXTINCTION PROCESSES PROCESSES

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EXTINCTION PROCESSES. EXTINCTION PROCESSES. EXTINCTION PROCESSES. Rare species are at risk due to : environmental stochasticity. Environmental Stochasiticity Examples – variable rate of increase. - PowerPoint PPT Presentation

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Page 1: EXTINCTION                   PROCESSES

EXTINCTION EXTINCTION PROCESSES PROCESSES

Page 2: EXTINCTION                   PROCESSES

EXTINCTION EXTINCTION PROCESSES PROCESSES

Time (years)

10 20 30 40 50 60Po

pu

lati

on

s P

ersi

stin

g (

%)

0

20

40

60

80

100

N < 16

N = 16-30

N = 31-50

N = 51-100

N > 100

Bighorn Sheep on Mountain Ranges

Source: Berger (1990, Cons. Biol. 4:91-98)

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EXTINCTION EXTINCTION PROCESSES PROCESSES

Rare species are at risk due toRare species are at risk due to::– environmental stochasticityenvironmental stochasticity

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Environmental Environmental StochasiticityStochasiticity

Examples – variable Examples – variable rate of rate of increaseincrease

Muskox population on

Nunivak Island, 1947-1964

(Akcakaya et al. 1999)

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Environmental Environmental StochasiticityStochasiticity- - Example of random KExample of random K

Serengeti wildebeest data set – recovering from Serengeti wildebeest data set – recovering from Rinderpest outbreakRinderpest outbreak– Fluctuations around K possibly related to rainfallFluctuations around K possibly related to rainfall

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EXTINCTION EXTINCTION PROCESSES PROCESSES

Rare species are at risk due toRare species are at risk due to::– demographic stochasticitydemographic stochasticity

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EXTINCTION EXTINCTION PROCESSES PROCESSES

Rare species are at risk due toRare species are at risk due to::– genetic stochasticitygenetic stochasticity

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EXTINCTION EXTINCTION PROCESSES PROCESSES

A. SpecializationA. Specialization– habitat restrictionhabitat restriction

proboscis monkeys and mangrove proboscis monkeys and mangrove swampsswamps

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EXTINCTION EXTINCTION PROCESSES PROCESSES

A. SpecializationA. Specialization– habitat habitat

restrictionrestriction– range range

restrictionrestriction golden-lion golden-lion

tamarinstamarins

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EXTINCTION EXTINCTION PROCESSES PROCESSES

A. SpecializationA. Specialization– habitat habitat

restrictionrestriction– range range

restrictionrestriction– body size and body size and

home-range home-range sizesize

maned wolfmaned wolf

Photo by Pete Oxford

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EXTINCTION EXTINCTION PROCESSES PROCESSES

A. SpecializationA. Specialization

B. CatastrophesB. Catastrophes– earthquakes, asteroidsearthquakes, asteroids– 5 mass extinctions5 mass extinctions– Cretaceous-Tertiary Cretaceous-Tertiary

extinctionsextinctions

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EXTINCTION EXTINCTION PROCESSES PROCESSES

A. SpecializationA. Specialization

B. CatastrophesB. Catastrophes– the human catastrophethe human catastrophe– humans have caused 75% of humans have caused 75% of

extinctions since 1600extinctions since 1600

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HUMANS AND HUMANS AND EXTINCTION EXTINCTION

A. Role of OverexploitationA. Role of Overexploitation– Lessons from North AmericaLessons from North America

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HUMANS AND EXTINCTION

HUMANS AND EXTINCTION

A. Role of Overexploitation– Bison

A. Role of Overexploitation– Bison

• presettlement: ca. 60 millionpresettlement: ca. 60 million• used food, hidesused food, hides• weapon against Native weapon against Native AmericansAmericans• by 1889: only 600by 1889: only 600

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HUMANS AND HUMANS AND EXTINCTION EXTINCTION

A. Role of OverexploitationA. Role of Overexploitation

B. Role of ExoticsB. Role of Exotics– introduced organismsintroduced organisms– cause of 20% of extinctions cause of 20% of extinctions

since 1600since 1600

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HUMANS AND HUMANS AND EXTINCTION EXTINCTION

B. Role of ExoticsB. Role of Exotics– Feral PigsFeral Pigs

game speciesgame species destroy destroy

understory and understory and groundcovergroundcover

effect on brown effect on brown honeycreeperhoneycreeper

expensive to expensive to exterminateexterminate

Po’ouli, n = 3 on 2/03

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HUMANS AND HUMANS AND EXTINCTION EXTINCTION

B. Role of ExoticsB. Role of Exotics– Domestic CatsDomestic Cats

domesticated to domesticated to kill pestskill pests

in 1/3 of U.S. in 1/3 of U.S. householdshouseholds

humans support humans support high densitieshigh densities

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HUMANS AND HUMANS AND EXTINCTION EXTINCTION

Cats: Cats: Effects on Native WildlifeEffects on Native Wildlife– WisconsinWisconsin: 19 million songbirds, : 19 million songbirds,

140,000 game birds per year140,000 game birds per year– Great BritainGreat Britain: 50 million small : 50 million small

mammals per yearmammals per year– AustraliaAustralia: endangerment of eastern : endangerment of eastern

barred bandicootbarred bandicoot

Photo: Ian McCann

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HUMANS AND HUMANS AND EXTINCTION EXTINCTION

C. Role of Human Population C. Role of Human Population SizeSize– most abundant mammal most abundant mammal

(Suzuki)(Suzuki)– currently about 6.7 billioncurrently about 6.7 billion– stabilize at ~9 billion by 2042?stabilize at ~9 billion by 2042?

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HUMANS AND HUMANS AND EXTINCTIONEXTINCTION

C. Role of Human Population C. Role of Human Population SizeSize

– Habitat DestructionHabitat Destruction– Habitat DisturbanceHabitat Disturbance

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CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE

www.usda.gov

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CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE

Richmond, VA – USDA photo

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CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE

Texas oil wells Russian coal power plant

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CONCLUSIONCONCLUSION

Conservation will fail unless:Conservation will fail unless:– human population is controlledhuman population is controlled– human resource use is moderatedhuman resource use is moderated

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Reintroductions & Translocations

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Wildlife ReintroductionsWildlife Reintroductions Does habitat Does habitat

remain?remain?

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Wildlife ReintroductionsWildlife Reintroductions

Viable Viable Population?Population?– PVAPVA

VORTEXVORTEX RAMASRAMAS

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Wildlife ReintroductionsWildlife Reintroductions

Viable Viable Population?Population?– PVAPVA

VORTEXVORTEX RAMASRAMAS Incorporate GISIncorporate GIS

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Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic

Considerations Considerations – –

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Genetic Considerations: Genetic Considerations: Why Should You Care?Why Should You Care?

Genetic variation is the underlying basis for Genetic variation is the underlying basis for adaptation to future environmental changeadaptation to future environmental change

Loss of genetic variation is often a direct Loss of genetic variation is often a direct consequence of species reintroductionconsequence of species reintroduction

Understanding how genetic loss occurs can help Understanding how genetic loss occurs can help to prevent management actions that decrease to prevent management actions that decrease the genetic diversity of reintroduced wildlife the genetic diversity of reintroduced wildlife speciesspecies

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Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic

ConsiderationsConsiderations– InbreedingInbreeding

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Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic

ConsiderationsConsiderations– Founder EffectFounder Effect

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Founder EffectFounder Effect

The reduction in overall genetic diversity The reduction in overall genetic diversity experienced as a consequence of population experienced as a consequence of population establishment from a limited sample of establishment from a limited sample of individualsindividuals– Most reintroductions and natural Most reintroductions and natural

colonization events exhibit Founder Effectscolonization events exhibit Founder Effects– The magnitude of the effect depends upon The magnitude of the effect depends upon

the number of animals translocated or the number of animals translocated or colonizing an areacolonizing an area

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Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic

ConsiderationsConsiderations– Genetic Genetic

BottleneckBottleneck

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BottleneckBottleneck

An event in which a population drops An event in which a population drops significantly in size and then recoverssignificantly in size and then recovers

Events such as habitat loss, over harvest, or Events such as habitat loss, over harvest, or reintroduction can create bottlenecks and the reintroduction can create bottlenecks and the magnitude of the effect on genetic diversity magnitude of the effect on genetic diversity depends upon:depends upon:

– Number of individuals at lowest pointNumber of individuals at lowest point– Length of time population remains depressedLength of time population remains depressed

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Genetic DriftGenetic Drift

Random fluctuations in gene frequencies due to Random fluctuations in gene frequencies due to temporal variance in survival and reproductiontemporal variance in survival and reproduction– Small populations drift more rapidly than large Small populations drift more rapidly than large

onesones– Higher reproductive and survival rates can Higher reproductive and survival rates can

slow the rate of genetic driftslow the rate of genetic drift– Genetic drift can result in loss of genetic Genetic drift can result in loss of genetic

diversity as well as increases in the frequency diversity as well as increases in the frequency of rare allelesof rare alleles

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InbreedingInbreeding

Mating of closely related individualsMating of closely related individuals Anytime genes that are alike by descent (i.e., Anytime genes that are alike by descent (i.e.,

from a shared ancestor) come together within from a shared ancestor) come together within individualsindividuals– Enhanced by slow population growth ratesEnhanced by slow population growth rates– Affected by mating systemAffected by mating system– Influenced by the relatedness of the initial Influenced by the relatedness of the initial

population founders (e.g. reintroductions)population founders (e.g. reintroductions)

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Hypothetical Source Population

Different Colors Represent Copies of Different Genes

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Trap and Transplant

Reintroduced Population

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Founder Effects

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Genetic DriftInbreeding

1010 Generation Bottleneck

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Genetic DriftInbreedingLoss of Allelic

Diversity Apparent

20 Generation Bottleneck

20

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Genetic DriftInbreeding

30 Generation Bottleneck

30

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Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic

ConsiderationsConsiderations– Marten Marten

reintroductionsreintroductions