1. BISC530: Biology Conservation Kedong Yin
Introduction
Habitat fragmentation
Demographic Processes on heterogeneous landscapes: Metapopulation dynamics

2. Demographic Processes: Population Dynamics on Heterogeneous Landscape
What is population demography?
Mechanisms of population regulation
Habitat-specific demography
Population viability analysis
The landscape approach

3. 1. What is population demography?
The study of population fluctuations due to birth, immigration, death, emigration (BIDE) population structure such as age structure, sex ratio and life history.
BIDE + Population structure: age and sex ratio + life history (e.g. insects, fish)
Birth
Popul. Size
Structure
Immigration
Emigration
Death

4. 6
1945
1985
1940
Years

5. Hong Kong Age Structure in 1998

6. Hong Kong Sex Ratio
Age 35
Female
Male

7. District 81 86 91
81-86
86-91
81-91
Tuen Mun
Sha Tin

8. Seal Population changes on two islands occupied by US Coastal Guard:
Juvenile survival is important in conserving seal populations
Tern Island
Coastal Guard in
Coastal Guard out
Green Island
Number of Seals
1980
1960
1970

9. 2. Mechanisms of population regulation: Environmental Factors
Abiotic:
Habitats
Light
Temperature
Precipitation
Nutrients
Biotic:
Intraspecific competition
Interspecific competition
Grazing/predation
Parasitism/disease

10. Population regulation: density-regulation
Mortality
Density-dependent
Density-independent
Rate of Birth or Death
Survival
Density-dependent
Population Density

11. Population regulation: Survival Strategy
Type I-Mammals
Survival Rate
Type II - Birds
Type III - Fish
Age

12. Population Regulation: prey-predator relationships
Abundance
Time

13. Mechanisms Allowing Species Diversity:
Resource Sharing and Niche Partitioning
Species 1 2 3
Relative Growth Rate
Resource State
Temporal or/and Spatial Variation
e.g. Habitats, Precipitation
Light, Temperature, Nutrients

14. Mechanisms Allowing Species Diversity:
Predator control
Predators
Relative Abundance
Species 1 2 3
Resource State

15. Mechanisms of Population Regulation:
A Hierarchy Approach
Land use change
Climate change
Succession
Disturbance
Landscape Level
Birth rates
Death rates
Immigration
Emigration
Sex ratio
Age structure
Population Level
Growth rates
Feeding rates
Habitat selection
Predator Avoidance
Individual Level

16. 3. Habitat-specific demography
Sources and Sinks:
Metapopulation Concepts

17. Equilibrium Theory of Island Biogeography:
Species richness is the balance between colonization and extinction rates
Colonization
Extinction
Near: N
Small: S
Rate of Colonization or Extinction
Large: L
Far: F
S-FS
S-FL
S-NL
S-NS
Low
High
Species Richness #

18. The key conservation legacies of the dynamic theory of island biogeography were:
1) Arriving at two most robust empirical generalizations of biology and ecology
(1) Extinction rates decline with population size
(2) Immigration and recolonization rates decline with increasing isolation
2) Species-area relationship
3) The metaphor of a refuge as an island
4) The interest in the fragility of the biota of individual refuges and causes of this fragility
5) The rules of refuge design

19. Metapopulation Sources and Sinks
Sources: good habitats where local reproductive success is greater than local mortality and individuals disperse outside their natural patch to find a place to settle and breed.
As little as 10% of a metapopulation in source habitats may be responsible for maintaining the 90% of the population found in the sinks
Sinks: poor habitats where local reproductive success is less than local mortality and the subpopulations rely on immigrations to avoid extinction

20. Implications of Sink and Source Concept for conservation:
1. Critical habitats should be defined by habitat-specific reproductive success and survivorship not population density -- important
(Until recently, critical habitats were defined as the places where a species was most common).
e.g. Peregrine Falcon: two subpopulations (northern California and southern California): northern subpopulation acts as a source for southern population.
2. Reserve design: identify sources and sinks
Management strategy for Peregrine Falcon focused on southern population (sink)

21. Metapopulation:
A population of a species that consists of several subpopulations linked together by immigration and emigration.

22. Metapopulation, linked by local subpopulations
Patch
Size
Spatial structure
Linkage

23. Metapopulation:
Note: Fragmented populations that is not linked are not considered to be a metapopulation.
Rescue Effect: local extinction of a subpopulation can be prevented by occasional immigrants that arrive from neighboring patches

24. A fundamental assumption of the original metapopulation concept
1) Space is discrete
2) It is useful and possible to distinguish between habitat patches that are suitable for the focal species and the rest of the environment, often called matrix
Three critical elements:
1) Density dependence in local population dynamics
2) Spatial asynchrony in local population dynamics (independent of other subpoulations)
3) Limited dispersal linking the local populations (migration has no real effect on local dynamics in the existing populations)

25. Sources and Sinks in a Metapopulation

26. Population Viability depends on:
1. Demographic uncertainty (stochasticity)
2. Environmental uncertainty (stochasticity)
3. Natural catastrophes
4. Genetic uncertainty (stochasticity)

27. Population Viability Analysis (PVA)
PVA is the study of how these four factors interact to determine extinction probability of a population to estimate MVP. The MVP is the product
MVP - Minimum Viable Population-imply some thresholds for the # of individuals that will insure (at some acceptable level of risk) that a population will persist in a viable state for a given interval of time
Population persistence analysis

28. Population Viability depends on:
1. Demographic uncertainty (stochasticity)
BIDE + age structure + sex ratio
Metapopulation structure
Fragmentation
the immediate precursor for extinction
independent of individuals

29. Population persistence in years
Immigration rate (individuals/year)

30. % Extinction

31. Population Viability depends on:
2. Environmental uncertainty (stochasticity)
A decrease in habitat quantity
Habitat disturbance or deterioration in quality
Realized via demographic stochasticity
A species also depends on habitats:
Types --- where a species is (distribution)
Quality (suitability) --- population features: density (abundance), fecundity, body size
Quantity (areas) --- survival of a species (big mammals)
Pattern (arrangement) --- habitat distribution for a metapopulation

32. Population Viability depends on:
3. Natural catastrophes
Sudden change in environments
Infrequent
In fact, they are large environmental changes
Fires
Storms
Hurricanes
Earthquakes
Volcanoes

33. 4. Genetic uncertainty (Stochasticity)
Mutation: an alteration of an allele (or alleles) into a new allele (new alleles) due to changes in molecules, gene sequences or chromosomes
Bottle neck: a sudden reduction in a population size causes a genetic drift
Genetic drift: random changes in allele frequency due to chance alone, often occurring in a small population (so-called sampling error)
Founder effect: a genetic drift occurs when a few individuals separate from a large population and establish a new one
Gene flow: the change in allele frequencies due to immigration or emigration

34. PVA Model Biology of Individuals Environmental Factors
Population Dynamics (demography)
Population Survival or Extinction

35. PVA Model Environmental disturbance Biology of Individuals
Environmental Factors
--Growth
--Population (P)
--Distribution
Population Dynamics (demography)
Genetic effective P size
Demographic uncertainty
Extinction
(Deterministic)
Extinction

36. Deterministic extinction:
extinction resulted from some inexorable change or force from which there is no hope of escape. E.g.
-- Deforestation
-- Glaciations
-- Removal a food source from animals

37. PVA Model Major loss of habitat Biology of Individuals
Environmental Factors
Population Dynamics (demography)
Extinction
(Deterministic)
Fragmentation
-- Population size
-- Distribution
Extinction
Demographic randomness

38. The case study of a bird: the Florida Scrub Jay
1. Metapopulation types
2. Biology of the bird
3. Spatial distribution of the bird
4. Metapopulation structure
Dispersal distance
Patch occupancy
Population viability analysis
Characterization of metapopulation
5. Conservation rules

39. Biology of the Bird, the Florida Scrub Jay
Florida’s only endemic bird species
Habitat specialist-scrub community on sandy infertile soils
Strong preference for low, open habitats with numerous bare openings and few or no pine trees, which are caused by frequent fires
Food: acorns in winter
Territorial defenders 10 ha per family
Juveniles dispersal after one year
The bird was listed as threatened species in 1987 by the U.S. Fish and Wildlife Service (USFWS)

40. Distribution of Florida scrub jay groups in 1993
Distribution of Florida scrub jay groups in Note the discontinuous distribution and variability in patterns of aggregation

41. Dispersal Distance (km)
A subpopulation buffer is the distance where occupancy rates remain high;
Accumulative
97%
Frequency
85%
3.5 km
6.7 km
Dispersal Distance (km)
From natal to breeding territories

42. The metapopulation buffer is the smallest interpatch distance where occupancy rates reach their minimum
Proportion of occupied patches
Interpatch Distance (km)

43. Distance between patches (km) Occupancy Proportions
Pairs
Distance between patches (km)
Occupancy Proportions
1-2
1-3
1-4
1-7
1-8 1
1.9
1.5 4 13
2/5 7 8 1

44. Statewide jay distribution with dispersal buffers
Statewide jay distribution with dispersal buffers. Shaded areas depict subpopulations within easy dispersal distance (3.5 km) of one another (191 separate subpopulations. Thick outer lines delineate demographically independent (42) metapopulations separated from each other by at least 12 km
A metapopulation
12 km
3.5 km
A subpopulation

45. Only Six subpopulations > 100 birds
Total 191 subpopulations
Frequency
Only Six subpopulations > 100 birds
Subpopulation Size (# of birds)
Numbers above the bars indicate the number of jay pairs

46. Frequency Metapopulation Size Nonequilibrium metapopulations
Total 42 metapopulations
Frequency
Metapopulation Size
Numbers above the bars indicate the number of jay pairs.

47. Metapopulation Types A. Patchy B. Classical C. Nonequilibrium
A dispersal buffer-an isoline of equal dispersal probability
A subpopulation
A. Patchy
B. Classical
C. Nonequilibrium
D. Mainland-Island

48. Nonequilibrium metapopulation
Functional subpopulation based on frequency of dispersal beyond them
Separate metapopulations based on poorly likelihood of dispersal among them
A set of small patches in which each has a high probability of extinction and among which little or no migration occurs.
Local extinction are not offset by recolonization, resulting in overall decline toward regional extinction.

49. Classical metapopulation
A set of small patches that are individually prone to extinction but large enough and close enough other patches that recolonization balances extinction.

50. Patchy metapopulation
Patches so close together that migration among them is frequent; hence the patches function over the long run as a continuous demographic unit.

51. Mainland-island metapopulation
A mixture of large and small patches close enough to allow frequent dispersal from an extinction-resistant mainland to the extinction-prone islands

52. Patch Size Highly connected Patchy Mainland- Mainland Patch isolation
Island
Classical
High
isolated
Nonequilibrium
Disjunct
All small
All large
Patch Size
Fig. 9.3.

53. Mn-Mainland
Md-midlands
I-islands
Total of 4 island subpopulations with 2 pairs in 1 subpopulation
Total of 8 island populations with 1 subpopulations of one pair

54. Examples of Nonequilibrium metapopulations
Fig North Gulf Coast of Florida: each of the 6 metapopulations contains fewer than 10 pairs of jays, except for the centrally located system that contains a single, midland-sized subpopulation

55. Fig Examples of a “classical” metapopulation from 3 counties in central Florida. Note the occurrence of jays in small islands of intermediate distance from one another.

56. Fig Portion of the largest mainland-midland-island metapopulation in interior Florida.. The large central subpopulation (enclosed by the thin black line) contains nearly 800 pairs of jays. Small subpopulations to the south and east are within known dispersal distance of the large, central mainland. A small metapopulation to the west (in DeSoto County) contains a single subpopulation of 21 territories.

57. Conservation Rules for the Florida scrub jay
Preserve the cores
Preserve all potentially viable metapopulations
Preserve or enhance existing persistence probabilities
Prohibit the splitting of a metapopulation
Maintain connectivity within a metapopulation

58. A comparison between island biogeography and metapopulation
Equilibrium: Species richness vs Population
Community approach vs population approach:
Community conservation (species richness-area relationship) vs focal species conservation
Island theory ignore the changes in the presence and absences of individual species
Among-patch movement

59. Shift to Metapopulation paradigm in conservation:
Metapopulation concept and approach is taking over the equilibrium theory of island biogeography in conservation biology
Shift in the conception of nature as an equilibrium world to non-equilibrium one
Population genetics – genetic drift and inbreeding in a small population, becomes important because conservation question like “what is minimum viable population?” needs to be addressed.
Species protection: the role of demographic and environmental stochasticity
Metapopulation concept incorporate spatial structure into population dynamics – most significant, linked to habitat fragmentation
Metapopulation models rescued small sites from their devaluation by island biogeography theory.

60. Landscape Approach: Landscape:
A mosaic of habitat patches across which organisms move, settle, reproduce and eventually die.
Heterogeneous within a landscape
Patchy distribution of individuals - patches

61. Landscape Approach Modeling - spatially explicit models Incorporate:
heterogeneous habitats
patchy distribution of organisms
Depict:
The landscape structure
The population demography
Project:
the outcome when a disturbance to habitats occurs, thus provide a management tool

62. Spatially explicit model
A metapopulation model incorporate the actual locations of organisms and suitable patches of habitat, and explicitly consider the movement of organisms among such patches.
Case of the Northern spotted owl

63. Case of Northern Spotted Owl
Habitat: mature, old-growth coniferous forests
Old, dense, large-trunk forest stands: foraging, cover, nesting, breeding, fledging of young
Life history: juvenile dispersal from their natal areas, in search for both a suitable site and a mate
Timber harvest, fire, clearing for agriculture and urban development reduce the habitat to 10% of original
Sparked the struggle between stakeholders
Very intense, prolonged battle
A petition for federal intervention under Endangered Species Act, -- given threatened status in 1990

64. Landscape simulation
suitable habitat, randomly scattered
Fig. 8 The results are based on 30 simulations.

65. Landscape simulation
Suitable habitats, 3 small blocks
Fig. 9. The results are based on 30 simulations.

66. Landscape simulation
Suitable habitats, a large block
Fig. 10 The results are based on 30 simulations.

67. Landscape simulation
Suitable habitat, 1 large irregular block
Fig The results are based on 30 simulations.

68. Landscape simulation
Suitable habitats, irregular blocks like riparian corridors
Fig The results are based on 30 simulations.

69. Suitable habitats, clusters with marginal habitat
Landscape simulation
Suitable habitats, clusters with marginal habitat
Standard deviations
Fig. 13 The results are based on 30 simulations.

71. Probability of Extinction
Endangered Species -- in danger of extinction throughout all or a significant portion of its range
Threatened species -- likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.
Critical Species -- facing a very high probability of extinction and require special conservation measures.
200
Safe
150
Vulnerable
Endangered
Years
100 50 50 20 10
Critical
0.2
0.4
0.6
0.8
1.0
Probability of Extinction