Transcript Document

BISC530: Biology Conservation
Kedong Yin
 Introduction
 Habitat fragmentation
 Demographic Processes on
heterogeneous landscapes:
Metapopulation dynamics
Key references: Meffe and Carroll and et al. 1997. The Principles of
Conservation Biology. Sinauer Assoc. Inc.
McCullough, DR. 1996. Metapopulation and Wildlife Conservation Chapter 9
http://teaching.ust.hk/~bisc530/
Introduction
Focal levels of
Conservation
Genetic material
Gene pools
Species
Biological
Conservation
Populations
Communities
Habitats
Ecosystems
Biosphere
Some postulates in conservation biology:
1. The diversity of organisms is good
2. The untimely extinction of populations and
species is bad
3. Ecological complexicity is good
4. Evolution is good
5. Biological diversity has intrinsic values
Biodiversity
 Species diversity remain to be the most important one
 Focusing on important species may provide short
cuts to conservation
 Keystone taxa: predominating ecological role
in community they may help to characterize
 Umbrella taxa: species providing “shelter”
for many others
 Flagship taxa: public appeal
 Indicator taxa: environmental change
Guiding Principles for Conservation Biology
Principle 1: Evolution is the basic axiom that
unites all of biology
(the evolutionary play)
Principle 2: The ecological world is dynamic and
largely non-equilibrial
(the ecological theatre)
Principle 3: The Human presence must be included
in conservation planning
(Humans are part of the play)
Habit Fragmentation:
1. Habitat fragmentation
2. Fragmentation and Heterogeneity
3. The Fragmentation Process
4. Insularization and Area effects
5. Biological Consequences of Fragmentation
Historical lessons on habitat loss:
 Classified Greek period -- the barren
landscape of deserts in the middle east
(Turkey, Syria, Irag and Iran) used to be
fragile woodlands
 Humid tropics -- shifting practices with
gaming, rotating practices in farming, not
possible in crowded world today
 Europe -- Great Britain, many forests
destroyed by 12th century, public forests
eliminated by the late 18th century, due to the
demand for charcoal supply
1. Habitat fragmentation:
 Reduction of the total amount of a habit type,
or perhaps of all natural habitat in a landscape
 Divide a continuous landscape into smaller,
more isolated patches
Critical habitat -- a specific area within the species
range with physical or biological features
either
(1) essential to conservation of the species
or
(2) which may require special management
considerations or protection
Fig. 9.1 Changes in
wooded area of
Cadiz Township,
Green Country,
Wisconsin, during
the period of
European settlement.
Wooded
area
1831
1882
1902
1950
2. Fragmentation and Heterogeneity
Patches (heterogeneity) vs continuous (homogeneous), a
matter of scales: zoom in or zoom out
Different vegetations
A side view of the mountain
Large disturbances like fires
create a course grained pattern
High mortality patch
Medium mortality patch
Low mortality patch
Small disturbances – a
fine-grained pattern
10 km
1 km
Different 7 phases of
canopy gaps by
death and fall of
individual trees
2. Fragmentation and Heterogeneity
Patches (heterogeneity) vs continuous (homogeneous), a
matter of scales: zoom in or zoom out
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Spatial scale (physical gradients, light, moisture, elevation)
Temporal (seasonality)
Disturbances (fires, storms)
Microhabitats
So, if habitat heterogeneity is good for diversity, what is the
difference between human-fragmented and natural patchy
landscape?
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Internal structure
Edge effects
Barriers
Evolutionary
3. The Fragmentation Process:
A
 Biological integrity -- Ecological system
 Disruption of continuity in pattern or
processes
Spatial scale
Temporal scale
B
C
Typical Habitat Fragmentation
A ranch subdivided into ranchettes
1957
Building
1983
1994
Effects when land is subdivided into ranchettes
Fragmentation
Population Density
Roads
Fences
Subsidized predators
Exotic Species
Nuisance problems
Wildlife generalists
Wildlife Specialists
Increase
Decreases in #
4. Insularization and Area effects:
 Area-species relationship: difference between
island and a patch of habitat, or
 A phenomenon of statistic sampling
 The equilibrium theory of island biogeography
S=cAZ or Log S = Log C + z Log A
S=species richness, A= area, c- constant
Island
S
Log S
Log S
Quadrats
A
A
Probability of occurrence of birds vs forest areas
Equilibrium Theory of Island Biogeography:
Rate of Colonization or Extinction
Species richness is the balance between colonization and extinction rates
Colonization
Extinction
Near: N
Small: S
Large: L
Far:
F
FS
NS FL
NL
Low
High
Species Richness #
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
3) Barriers and Isolation
4) Crowding effects
5) Local and Regional Extinctions
6) Species vulnerable to fragmentation
7) Edge Effects
8) Changes in Species Composition
9) Effects on Ecological Processes
1) Speciation
Speciation: a process a new species is formed.
Speciation process is ultimately a genetic
divergence between populations through time,
reflecting local adaptation
How selection works: giraffe long neck
Selective pressure toward a longer-necked, taller animal
Selective
pressure stops
Short-necked animals starve and die. Gene for shorter neck
does not enter gene pool
Many generations
Gradual allopatric speciation
Founder model or
Quantum Speciation
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Gradual Allopatric Speciation: Arctic vs Gray fox
Subpopulations spread northward and southward and separate
Conditions differ giving different selective pressures
causing evolution into different species
Adaptations to cold
climate: heavy fur; short
tail, ears, legs, and nose;
light color
Arctic Fox
Adaptations to warm
climate: thin fur; long
tail, ears, legs, and
nose; dark color
Gray Fox
Exmaple of quantum speciation of finches
Warbler
Woodpecker
Small
insectivorous
Large
insectivorous
Vegetarian
Cactus Ground
Sharp-Beaked
Sharp-Beaked
Ground
Ground
Small Ground
Medium
Ground
Large
Ground
Darwin’s finches. The similarities among these birds attest
to their common ancestor. Selective pressures adapting
subpopulations to feed on different foods has caused their
modification and speciation.
Geographic modes of speciation:
1) Gradual allopatric speciation
Reproductive isolation is a result of divergence. If
divergence is relatively short, the two groups comes into
second contact-hybrid-no advantage -stable . If long,
hybrids -- natural selection works -- become
distinguishable specie.
2) Founder model or quantum speciation
 small gene pool
 gene drift -- genetic drift--rapid and substantial genetic
change
 speciation -- rapid
Effects of fragmentation of habitats on the speciation
Two scenarios:
1) quantum speciation occurs rapidly and results in
several species
2) local extinction -- more quickly than speciation
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2) Initial Exclusion
One of the most rapid and obvious effects of
fragmentation: elimination of the species by the initial
exclusion
Home ranges are destroyed, endemic species are
sometimes quite restricted in its distribution, many rare
species are endemics with narrow distributions
Species with narrow distribution are vulnerable when
their habitat is fragmented
Endemic species: species only exist in this country, not
in other countries; or in this area not in other areas.
3) Barriers and Isolation
A species require several patches to survive
AA
B
A constellation of separate habitat patches may be critical
to the survival of individuals or populations. When a
species requires several patches (green area) to survival,
then species in site A would survive better.
A species require different habitats (A and B) to
survive
A
A
B
B
Many animals require a suite of different habitats or
resources to survive. A population in Site A in the
proximity of different habitat B would survive better than
in Site B.
Roads as barriers to the
movement of small
animals
Carabid beetles releasing
experiment
Lines – movement of
marked bettles between
capture and recapture
Beetle density
N>100
N>50
N>20
3) Barriers and Isolation
A constellation of separate habitat patches – critical to the
survival of a population
A mix of different habitats with different resourcesimportant
Barrier: species specific
Roads as a major barrier to many species
Barrier effects are both relative and cumulative
Structural contrast between fragmented habitats and the
matrix for the species is one measure of fragmentation, as
the landscape around fragments is altered, the functional
isolation of these fragments increases
Dams or other marine engineering projects
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
3) Barriers and Isolation
Barriers are species specific
Relative and cumulative
4) Crowding effects
4) Crowding Effects
Population densities may initially increase in the
fragment when the fragment is isolated
This packing phenomenon – “crowding on the ark”
The initial increase is often followed by the population
collapse
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
Home ranges are destroyed, endemic species are sometimes
quite restricted in its distribution
3) Barriers and Isolation
Barriers are species specific
Relative and cumulative
4) Crowding effects
5) Local and Regional Extinctions
Even common species can disappear from the fragments
when the fragments are altered.
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
Home ranges are destroyed, endemic species are sometimes
quite restricted in its distribution
3) Barriers and Isolation
Barriers are species specific
Relative and cumulative
4) Crowding effects
5) Local and Regional Extinctions
6) Species vulnerable to fragmentation
Species vulnerability
 Abundance
 Extent of ecological specialization
 Geographical range
6) Species vulnerable to fragmentation
Naturally rare species:
a) Species with limited or patchy geographic distributions
(e.g. endemic species)
b) Species with low population densities (e.g. animals
with a large home range)
Wide-ranging species: large carnivores needs a large area
for food hunting or seasonal movement
Nonvagile species: species with poor dispersal abilities
may not travel far from their birth place, e.g. many
insects of old growth forests
Species with low fecundity: species with low reproductive
capacity
6) Species vulnerable to fragmentation
Species with short life cycles: more vulnerable than
longer-lived species
Species dependent on patchy or unpredictable resources
or otherwise highly variable in population size
Grounded Nesters: nesting on or near the ground
Large-patch or interior species: species living in the
interior of a habitat, thus vulnerable to fragmentation of
their habitat
Species vulnerable to human exploitation or persecution
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
Home ranges are destroyed, endemic species are sometimes
quite restricted in its distribution
3) Barriers and Isolation
Barriers are species specific
Relative and cumulative
4) Crowding effects
5) Local and Regional Extinctions
6) Species vulnerable to fragmentation
7) Edge Effects
7) Edge Effects
Loss of quail eggs
There is edge if a habitat island
is different from the
surrounding landscape
There is a gradient of
environmental factors across
the edge
Ecological trap: animals are
attracted to edge habitat
The structural contrast to the surrounding landscape is an
indicator of the strength of edge effects
The ratio of the edge length to the interior area is a
measure of the edge effects
No birds bred
successfully
A
39 ha
A comparison of
breeding success of
fragmentation sensitive
birds (16 species) in
two forest fragments
with similar total areas,
but vastly different
core areas (forest
interior).
A is entirely edge habitat
(light);
B
20 ha
47 ha
6 species / 16 species bred in
core area
B contains 20 ha of
interior habitat.
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
Home ranges are destroyed, endemic species are sometimes
quite restricted in its distribution
3) Barriers and Isolation
Barriers are species specific
Relative and cumulative
4) Crowding effects
5) Local and Regional Extinctions
6) Species vulnerable to fragmentation
7) Edge Effects
8) Changes in Species Composition
5. Biological Consequences of Fragmentation:
1) Speciation
2) Initial exclusion:
Home ranges are destroyed, endemic species are sometimes
quite restricted in its distribution
3) Barriers and Isolation
Barriers are species specific
Relative and cumulative
4) Crowding effects
5) Local and Regional Extinctions
6) Species vulnerable to fragmentation
7) Edge Effects
8) Changes in Species Composition
9) Effects on Ecological Processes
Species Persistence in a fragmented landscape:
3 options
 Survive well or thrive in a matrix of
human land uses: weedy species
 Maintain viable population within
individual habitat fragments: species with
a small home range
 Highly mobile: some birds
Habit Fragmentation:
1.
2.
3.
4.
5.
Habitat fragmentation
Fragmentation and Heterogeneity
The Fragmentation Process
Insularization and Area effects
Biological Consequences of
Fragmentation