EXTINCTION EXTINCTION PROCESSES 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)
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at risk due toRare species are at risk due to::– environmental stochasticityenvironmental stochasticity
Environmental Environmental StochasiticityStochasiticity
Examples – variable Examples – variable rate of rate of increaseincrease
Muskox population on
Nunivak Island, 1947-1964
(Akcakaya et al. 1999)
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
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at risk due toRare species are at risk due to::– demographic stochasticitydemographic stochasticity
EXTINCTION EXTINCTION PROCESSES PROCESSES
Rare species are at risk due toRare species are at risk due to::– genetic stochasticitygenetic stochasticity
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization– habitat restrictionhabitat restriction
proboscis monkeys and mangrove proboscis monkeys and mangrove swampsswamps
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization– habitat habitat
restrictionrestriction– range range
restrictionrestriction golden-lion golden-lion
tamarinstamarins
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
EXTINCTION EXTINCTION PROCESSES PROCESSES
A. SpecializationA. Specialization
B. CatastrophesB. Catastrophes– earthquakes, asteroidsearthquakes, asteroids– 5 mass extinctions5 mass extinctions– Cretaceous-Tertiary Cretaceous-Tertiary
extinctionsextinctions
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
HUMANS AND HUMANS AND EXTINCTION EXTINCTION
A. Role of OverexploitationA. Role of Overexploitation– Lessons from North AmericaLessons from North America
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
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
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
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
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
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?
HUMANS AND HUMANS AND EXTINCTIONEXTINCTION
C. Role of Human Population C. Role of Human Population SizeSize
– Habitat DestructionHabitat Destruction– Habitat DisturbanceHabitat Disturbance
CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE
www.usda.gov
CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE
Richmond, VA – USDA photo
CONSERVATION AND CONSERVATION AND HUMAN RESOURCE USEHUMAN RESOURCE USE
Texas oil wells Russian coal power plant
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
Reintroductions & Translocations
Wildlife ReintroductionsWildlife Reintroductions Does habitat Does habitat
remain?remain?
Wildlife ReintroductionsWildlife Reintroductions
Viable Viable Population?Population?– PVAPVA
VORTEXVORTEX RAMASRAMAS
Wildlife ReintroductionsWildlife Reintroductions
Viable Viable Population?Population?– PVAPVA
VORTEXVORTEX RAMASRAMAS Incorporate GISIncorporate GIS
Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic
Considerations Considerations – –
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
Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic
ConsiderationsConsiderations– InbreedingInbreeding
Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic
ConsiderationsConsiderations– Founder EffectFounder Effect
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
Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic
ConsiderationsConsiderations– Genetic Genetic
BottleneckBottleneck
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
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
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)
Hypothetical Source Population
Different Colors Represent Copies of Different Genes
Trap and Transplant
Reintroduced Population
Founder Effects
Genetic DriftInbreeding
1010 Generation Bottleneck
Genetic DriftInbreedingLoss of Allelic
Diversity Apparent
20 Generation Bottleneck
20
Genetic DriftInbreeding
30 Generation Bottleneck
30
Wildlife ReintroductionsWildlife Reintroductions Genetic Genetic
ConsiderationsConsiderations– Marten Marten
reintroductionsreintroductions