Conservation at the Population

1
Conservation at the Population Species Levels

• Chapter 3

2
Main Ideas

• Conserving Species by Conserving Populations
• Problems of Small Populations
• Natural History Ecology
• Establishment of New Populations
• Ex Situ Conservation Strategies
• Legal Protection of Species

3
Conserving Species, Conserving Populations

• Preserve as many species as possible
• Preserve greatest possible area of habitat
• Minimum Viable Population
• MVP
• smallest isolated population with 99 chance of
  remaining extant for 1000 years
• take into account catastrophes
• genetic, natural, demographic
• Minimum Dynamic Area
• MDA
• amount of habitat necessary to maintain the MVP

4
Problems of Small Populations

• Subject to rapid decline and local extinction
• genetic problems
• demographic fluctuations
• environmental fluctuations in
• predation
• competition
• incidence of disease
• food supply
• natural catastropheres
• fires, floods, droughts

5
Problems of Small Populations

• Loss of Genetic Variability
• Genetic Drift
• Inbreeding Depression
• Outbreeding Depression
• Loss of Evolutionary Flexibility

6
Loss of Genetic Variability

• Allows populations to adapt
• Genetic Drift
• alleles vary in frequency
• small populations may have frequency changes
  within generations
• alleles with low frequency have probability of
  being lost
• Equation
• H 1 - 1/2N2
• population of 50
• 99 heterozygosity after one generation
• 90 after 10
• population of 10
• 90 after 1 generation, 60 after 10 generations

7
Maintaining Genetic Diversity
8
Inbreeding Depression

• Small population size can result into close
  relatives mating
• Results
• fewer offspring
• weak or sterile offspring
• allows expression of harmful alleles

9
Outbreeding Depression

• Outbreeding
• mating between separate populations
• occurs when individuals cannot find mates within
  population
• lack of compatibility causes problems
• weak or sterile offspring
• result may be not having precise combination of
  genes which allowed them to survive under
  particular conditions and extremes
• may blur species boundaries

10
Loss of Evolutionary Flexibility

• Uniquely suited for environmental conditions
• present or future
• Result of rare alleles or precise combinations of
  alleles
• Loss of flexibility results
• limit ability of population to respond to
  long-term chances
• pollution
• disease
• climate change

11
Effective Population Size

• Depends on species
• Franklin proposed 50
• would lose only 1 variability per generation
• based on work with domestic animals only
• 500 would have mutation balancing variability
  lost
• 50/500 rule
• isolated populations at least 50, preferrably 500
  for variability
• Effective population size
• smaller than actual population size
• not all individuals can produce offspring
• age, poor health, sterility
• malnutrition, small body size, lack of mate
  (society structure)

12
Problems of Small Populations

• Effective Population Size
• Unequal Sex Ratio
• Variation in Reproductive Output
• Population Fluctuations
• Bottlenecks
• Founder Effects

13
Unequal Sex Ratio

• Unequal numbers of males/females
• random chance
• monogamy
• social systems
• Equation
• Ne 4NmNf
• Nm Nf

14
Variation in Reproductive Output

• Number of offspring varies considerably
• few
• thousands
• plants especially characterize this
• Results in few individuals disproportionately
  represented in gene pool of next generation

15
CONSERVATION OF AMERICAN CRANES

• A Case Study by Tyler E. Hundley

16
Grus americanaWhooping Crane

• Small, unstable populations
• 155 individuals
• Aquatic feeders
• Population increase very slow

• A Case Study by Tyler E. Hundley

17
Grus canadiensisSandhill Crane

• Well established populations
• 500,000
• Food vegetables
• Responded well to conservation
• Where controlled hunting
• Protected areas

18
Comparison

• Small differences in biology and behavior
• Whooping crane population troubled
• Sandhill crane population hearty
• Both species lay two eggs
• Sandhills raise offspring successfully
• Whooping only 15 success
• Chicks kill siblings

19
Human disturbance

• Sandhill cranes nest in remote areas
• Whooping cranes nest in agricultural sites
• Loss of preferred wetlands
• Bird watchers and tourists

20
Bottlenecks Founder Effects

• Bottleneck
• When a population is greatly reduced in size
• Rare alleles will be lost
• If no individual survives with those alleles
• Must reproduce to pass alleles on
• Founder Effect
• When a few individuals leave a large population
• Establish a new population
• New population has less genetic variability than
  original, larger
• Lower probability of persisting

21
Demographic Variation

• Variation in age demographics
• individuals too old to reproduce
• no individuals of reproductive age in population
• absence of offspring over several years
• Demographic stochasticy
• occurs once a population becomes too small
• population has higher probability of going
  extinct
• especially greater in some species with
• lower birth rates, reproduction late in life
  cycle
• Allele Effect
• animals unable to find mates (widely dispersed
  populations)

22
Seed Dispersal Hartman Prairie Restoration
23
Environmental Variation Catastrophes

• Environmental Stochasticity
• Random variation in biological/physical
  environment
• increased/decreased rainfall impacts plant growth
  (food supply)
• Natural Catastrophes
• droughts
• storms
• foods
• earthquakes
• volcanic eruptions
• fires
• cyclical die-offs in surrounding community

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• Extinction Vortices
• More genetic drift, less ability to adapt
• More inbreeding depression
• Population more subdivided by fragmentation
• More demographic variation
• Lower effective population size
• environmental variation, catastrophes, climate
  change
• habitat destruction, degradation, fragmentation
• overharvesting, exotic species
• Extinction

25
Study Guide

• 7. Consequences of low genetic variability
• Inbreeding depression
• When individuals mate with close relatives such
  as parents, siblings, and cousins. This results
  in fewer offspring, or offspring that are weak or
  sterile. It allows the expression of harmful
  alleles. It allows therefore, harmful recessive
  alleles to become expressed in the homozygous
  form, with resulting harmful effects on the
  offspring.

26
Study Guide

• 7. Consequences of low genetic variability
• Loss of evolutionary flexibility
• Loss of genetic variability may limit the
  ability of a population to respond to long-term
  changes in the environment. Rare alleles and
  unusual combinations of alleles that confer no
  immediate advantages may be uniquely suited for a
  future set of environmental conditions. When
  rare alleles are lost in small populations and
  heterozygosity declines, the population has few
  genetic options available.

27
Problems of Small Populations

• Loss of Genetic Variability
• change F 1 / Z Ne
• Unequal Sex Ratio
• Ne - 4NmNf divided by Nm Nf
• Variation in Reproductive Output
• Population Fluctuations Bottlenecks

28
Study Guide

• 1. List problems of small populations.

29
Study Guide

• 2. Minimum viable population size.
• The smallest number of individuals necessary to
  prevent the population from going extinct.

30
Effective Population Size

• How many individuals are needed to maintain
  genetic variability in a population?
• Smaller than actual population size
• Unequal sex ratio
• Variation in reproductive output
• Population fluctuations
• Bottlenecks/ founder effects

31
Study Guide

• 4. List the factors to consider in effective
  population size.and explain EACH.

32
Study Guide

• 5. Support the correlation of population size
  with genetic variability.
• This is found by measuring the loss in genetic
  variability over time in repeatedly censused
  populations.

33

• As a population becomes smaller
• It tends to lose genetic variability by chance,
• A process called genetic drift.
• Leading to inbreeding depression and a lack of
  evolutional flexibility.

34
Study Guide

• 6. What is the significance of a genetic
  bottleneck?
• A population may occasionally be severely
  reduced in size due to some environmental or
  demographic event that kills all but a few
  individuals.

35

• When a population is greatly reduced in size,
  rare alleles in the population will be lost if no
  individuals possessing those alleles survive.
• With few alleles present and a decline in
  heterozygosity, the overall fitness of the
  individuals in a population declines.

36
Study Guide

• 6b. What is the significance of the founder
  effect?
• The founder effect occurs when a few individuals
  leave a large population to establish a new
  population.

37
Study Guide

• 6. Explain the Ngorongoro Crater lion
  population.
• The lions of Ngorongo Crater in Tanzania are an
  example of a well studied genetic bottleneck.
  The lion population consisted of 60-75
  individuals until an outbreak of biting flies
  reduced the population to 9 females and 1 male in
  1962.
• Two years later, an additional 7 males immigrated
  to the crater. As a result, the small number of
  founders, the isolation of the population, and
  the variation in reproductive success among
  individuals has created a genetic bottleneck.

38

• The genetic bottleneck exists even though the
  population has increased to 125 animals. In
  comparision with the large serengeti lion
  population nearby, the Crater lions show
• reduced genetic variability
• high levels of sperm abnormalities
• and reduced reproductive rates.

39
Problems of Small Populations

• Demographic variation
• demographic stochasticity
• birth/death/age ratio
• Allee effect p. 117

40
Study Guide

• 7. Define demographic stochasticity and give an
  example.
• In an adeal stable environment, populations
  increase until they reach the carrying capacity.
  For whatever reason, population number drop
  because of habitat loss or degradation, exotic
  species, etc once a population drops below 50
  individuals, demographic variation begins to
  become important and the population has a higher
  probability of going extinct.

41

• Random demographic variation is also known as
  demogrphic stoasticity, and becomes greater as
  population size gets smaller, resulting in a
  greater probability of extintion due to chance
  also. The chance of extinct is also greater in
  species that have low birth rates, such as
  elephants. As an example, the Dusky Seaside
  Sparrow, with 5 individuals, no males.

42
Problems of Small Populations

• Environmental Variation Catastrophes
• environmental stochasticity

43
Problems of Small Populations

• Extinction Vortexes
• Environmental variation
• Catastrophic events
• Habitat destruction
• Environmental degradation
• Habitat fragmentation
• Overharvesting
• Effects of exotic species

44
Natural History

• Ecological questions
• environment
• distribution
• biotic interactions
• morphology
• physiology
• demography
• behavior
• genetics

45
Natural History

• Gathering Natural History Information
• published literature
• unpublished literature
• fieldwork

46

• Monitoring Populations
• Indicator Species
• Inventory
• Number of individuals within a population
• Population Survey
• Repeatable sampling, estimates density
• Demographic Studies
• Follow known individuals

47
Monitoring Fish Populations Caseys Lake
48

• Population Viability Analysis
• Extended demographic analysis
• determines species ability to persist in an
  environment
• species requirements compared to environmental
  resources

49

• Metapopulation
• core
• satellite areas
• variations
• 3 independent populations
• 3 interacting populations
• metapopulation with large core and several
  satellites
• metapopulation with complex interactions
• recognize local populations are dynamic
• endemic Furbish lousewort

50
Establishment of New Populations

• Three Approaches
• Reintroduction
• releases captive bred or wild collected to
  historic range
• Augmentation
• releasing individuals into existing population to
  increase gene pool
• Introduction
• moving individuals outside of historic range in
  hope of establishing new populations

51
Establishment of New Populations

• Considerations for Successful Programs
• expensive
• difficult
• serious long-term commitment
• political
• educational value
• extensive care perhaps

52
Establishment of New Populations

• Social Behavior of Released Animals
• Consider social organization behavior
• Establishing New Plant Populations
• Re-establishment Programs and the Law

53
Ex Situ Conservation Programs

• Off-site Preservation
• Zoos
• Innovative Reproductive Techniques
• Cross fostering
• Artificial insemination
• Artificial incubation
• Embryo transfer
• Aquariums
• Botanical Gardens Arboretums
• Seed Banks

54
Establishment of New Populations

• Seed Banks
• Sampling strategies for wild species
• Conservation of tree genetic resources
• Seed Savers

55
Conservation Categories of Species

• Extinct
• Extinct in the Wild
• Critically Endangered
• Endangered
• Vulnerable

• Conservation Dependent
• Near Threatened
• Least Concern
• Data Deficient
• Not Evaluated

56
Establishment of New Populations

• Iowas State Categories
• Extinct
• Endangered
• Threatened
• Special Concern

57
Establishment of New Populations

• IUCN
• Critical Species
• gt50 probability of extinction within 5 years or
  two generations
• Endangered
• 20-50 probability of extinction within 20 years
  or 10 generations
• Vulnerable
• 10-20 probability of extinction within 100 years

58
IUCN Categories

• Critically endangered
• 50 extinction probability within 10 years or 3
  generations
• Endangered
• 20 extinction probability within 20 years or 5
  generations
• Vulnerable
• 10 probability of extinction within 100 years

59
Classification Determinants

• Observable decline in numbers of individuals
• Size of geographical area, number of populations
• Number individuals living, number breeding
• Expected decline
• Probability of going extinct