Transcript Marmota vancouverensis

Introduction – Landscape Ecology
• Landscape Ecology: Study of landscape
structure and processes.
– Landscape: Heterogeneous area composed of
several ecosystems.
– Landscape Elements: Visually distinctive
patches in an ecosystem.
Vancouver Island marmot
(Marmota vancouverensis)
~100 left
Isolated from hoary and
Olympic marmots
Vancouver Island marmot
(Marmota vancouverensis)
Natural tree succession
Vancouver Island marmot
(Marmota vancouverensis)
• Logging – disjunct patches
- max. dispersal = 7 km
• Climate
• Prey-Predator Dynamics
Human Land Use Practices
1) Agriculture
2) Suburban Development
Let’s pick on Indiana:
•
•
97% of land in state = privatelyowned
In central Indiana,
• 70+% of land in row crop
• <10% in forest
• Urban sprawl intensifying
Human Impacts
Ecosystem simplification: elimination of
species from food webs via human
alterations to land
Example: vertebrate communities in ag.
landscapes
Intensive Agriculture
&
Clean Farming
Timber Extraction
&
Fragmentation
Formation of
Terrestrial “Islands”
Habitat Fragmentation
• Process of breaking contiguous unit into
smaller pieces; area & distance
components
• Leads to:
< remnant patch size
> edge:interior ratios
> patch isolation
< connectivity
• Community & Ecosystem processes
altered
Formation of
Terrestrial “Islands”
Habitat Loss vs. Habitat Fragmentation
#patches
Patch isolation
Patch size
Edge
What about
aquatic systems?
What about
aquatic systems?
Con.Bio 12(6)
Habitat Fragmentation
• area-sensitive species: species that
require minimum patch size for daily
life requirements
• Edge effects: influence of factors from
outside of a patch
Increased Edge Habitat
Increased Edge Habitat
Edge Effects
• Habitat surrounding a patch can:
- change abiotic conditions; e.g., temp.
- change biotic interactions, e.g.,
predation
Example of nest predation = edge effect of
approximately 50 m into forest patch
Habitat Fragmentation
• First-Order Effects: fragmentation leads
to change in a species’ abundance and/or
distribution
Habitat Fragmentation
• Higher-Order Effects: fragmentation
indirectly leads to change in a species
abundance and/or distribution via altered
species interactions
HABITAT FRAGMENTATION
GroundNesting Birds
- Abundance
– - Distribution
Avian Competitors
Avian Prey
Brood Parasites
Predators
- Abundance
+ - Distribution
- Foraging Behaviors
–
+
–
+
Parasites
- Abundance
- Distribution
REPRODUCTIVE SUCCESS
Habitat Fragmentation: SpeciesSpecific Sensitivity?
• Rare species = more vulnerable
• Wide ranging species = large-area
requirements
• Species with reduced mobility = more
vulnerable
• Species with low fecundity (related to
rarity?)
• Species with short life cycle (or multistage life cycle?)
Habitat Fragmentation: SpeciesSpecific Sensitivity?
• Ground-nesting birds may be more
vulnerable (30-60% reduction in last 25
yrs)
• Interior-dependent species
• Species vulnerable to human exploitation
or disturbance
• Specialist species?
Habitat Fragmentation: SpeciesSpecific Sensitivity?
Generalizations are a good start
(= hypotheses?), but a little more
complex than that……
Gehring and Swihart. 2003.
Biological Conservation
109:283-295
Spatial and Temporal
Ecology of Raccoons
Gehring et al. In prep.
Swihart et al. 2003.
Diversity and
Distributions 9:1-8.
Brown and Litvaitis. 1995. Canadian Journal of Zoology
73:1005-1011
Implications of Changes in Scale
Insects sampled at 10-m intervals for 100 m
45
40
35
30
25
Predator
Prey
20
15
Pr
ey
Pr
ed
at
or
10
5
0
Implications of Changes in Scale
Insects sampled at 2000-m intervals for 20,000 m
45
40
35
30
25
Predator
Prey
20
15
Pr
ey
Pr
ed
at
or
10
5
0
Landscape Pattern
I.
Landscape Components
(attributes of features or spatial elements)
A.
B.
C.
Composition
Configuration
Connectivity
Relative to landscape spatial elements….
How much of the area is comprised of each type of spatial element?
How are spatial elements arranged in space?
How do these attributes change through time?
How does one quantify landscape pattern?
How do biotic communities interact with pattern?
Causes of Landscape Pattern
I.
Abiotic Factors
II. Biotic Factors
III. Human Landuse
IV. Disturbance & Succession
Causes of Landscape Pattern
• Abiotic Factors
– Variance in climate (biogeographic influences)
– Variance in landform (more localized constraints;
microclimates)
Common N.A. trees –
contractions &
radiations in
distribution
Influence of landform – spatial pattern of species distribution
Causes of Landscape Pattern
• Biotic Factors
– Competition
– Predation
Causes of Landscape Pattern
• Human Land Use
– Prehistoric, Historic, Present Effects
• Shift from nomadic hunter-gatherer to farming systems
Human Land Use Practices
1) Agriculture
2) Suburban Development
*Landuse / Landcover Data from
USGS sources (typically
resolution to 30 m)
Causes of Landscape Pattern
• Human Land Use
– Present Effects
• Extraction of natural resources
• Patterns of development
• Transportation networks
Roads: Formation of Barriers in Landscapes
Clearcuts and National Forest Management
Patch Clearcuts
Landscape Processes
• Landscape structure influences processes
such as the flow of energy, materials, and
species between the ecosystem within a
landscape.
Landscape Structure and
Dispersal of Small Mammals
Habitat Patch Size and Isolation
and Density of Butterfly
Populations
Organisms and Landscape
Structure
• African elephants knock down tress.
– Change woodland to grassland.
• Kangaroo Rats dig burrow systems that
modify soil structure and plant distributions.
• Beavers cut trees, build dams and flood
surrounding landscape.
– At one time, beavers modified nearly all
temperate stream valleys in Northern
Hemisphere.
Organisms and Landscape
Structure
• Johnston and Naiman documented
substantial effects of beavers on landscape
structure.
– Over 63 yrs, area created by beavers increased
from 200 ha to 2,661 ha.
– Changed boreal forest landscape to complex
mosaic.
Organisms and Landscape
Structure
• Beaver activity between 1927-1988
increased quantity of most major ions and
nutrients in impounded areas. Three
possible explanations:
– Impounded areas may trap materials.
– Rising waters captured nutrients formally held
in vegetation.
– Habitats created by beavers may promote
nutrient retention by altering biogeochemical
processes.
Introduction – Geographical Ecology
• MacArthur defined geographical ecology as
the search for patterns of plant and animal
life that can be put on a map.
– Above level of landscape ecology.
– Vast breadth
• Chapter only focuses on a few aspects.
Oceanic Island = Terrestrial Island ?????
Island Area and Species Richness
• Preston found fewest bird species live on
smallest islands and most species on largest
islands.
• Nilsson et.al. found island area was best
single predictor of species richness among
woody plants, carabid beetles, and land
snails.
Island Area and Species Richness
Species-Area Relationship
S = cAz
S = # of species
A = island area
• Positive correlation between island size
& number of species
• Applies to terrestrial “islands” also
Habitat Patches on Continents:
Mountain Islands
• As Pleistocene ended and climate warmed,
forest and alpine habitats contracted to the
tops of high mountains across American
Southwest.
– Woodlands, grasslands, and desert scrub,
invaded lower elevations.
– Once continuous forest converted to series of
island-like fragments associated with
mountains: Montane.
Lakes as Islands
• Lakes can be considered as habitat islands.
– Differ widely by degree of isolation.
• Tonn and Magnuson found the number of species
increases with the area of an insular environment.
• Barbour and Brown found positive relationship
between area and fish species richness.
Lakes as Islands
Marine Islands
• MacArthur and Wilson found isolation
reduces bird diversity on Pacific Islands.
• Williamson summarized data from
relationship between island area and species
richness in Azore Islands:
– Birds show clear influence of isolation on
diversity, ferns do not.
– Land birds fly across water barriers, and ferns
produce large quantities of light spores easily
dispersed in the wind.
Marine Islands
Isolation and Habitat Islands on
Continents
• Lomolino et.al. found a strong negative
relationship between isolation and the
number of montane mammal species living
on mountaintops across the American
Southwest.
Equilibrium Model of Island
Biogeography
• MacArthur and Wilson: Model explaining
patterns of species diversity on islands as
result of immigration and extinction rates.
– Reasoned rates of immigration would be
highest on new island with no organisms.
• As species began to accumulate, rate of immigration
would decline since fewer arrivals would be new
species.
Equilibrium Model of Island
Biogeography
• Predicted rate of extinction would rise with
increasing number of species on an island
for three reasons:
– Presence of more species creates a larger pool
of potential extinctions.
– As number of species increases, population size
of each must diminish.
– As number of species increases, potential for
competitive interactions between species will
increase.
Equilibrium Model of Island
Biogeography
• Point where two lines cross predicts the number of
species that will occur on an island.
• Proposed rates of extinction on islands would be
determined mainly by island size.
– LG near islands will support highest number.
– SM far islands will support lowest number.
– SM near and LG far will support intermediate number.
Island Biogeography
• equilibrium model suggesting that the
number of species occurring on an
island represents a balance between
immigration (in) and extinction (out)
• Robert MacArthur & E.O. Wilson
Experimental Island
Biogeography
• Simberloff and Wilson studied insect
recolonization in Florida Keys.
– Chose 2 stands of mangroves as control islands,
and 6 others as experimental islands.
• Defaunated islands
– Followed recolonization for 1 yr.
» Species number stayed constant, but composition
changed considerably.
Experimental Island
Biogeography
Colonization of New Islands by
Plants
• Rydin and Borgegard found variation in spp.
richness correlated positively with island
area and accounted for 44-85% of variation
in species richness among islands.
– Small and medium islands continued to
accumulate species.
– Large islands attained equilibrium of
immigration and extinction.
• Difficult to separate effects of habitat diversity from
area effects.
Manipulating Island Area
• Simberloff tested effect of island area on
species richness.
– In all cases where area was reduced, species
richness decreased.
• Richness on control island increased slightly.
– Islands with reduced area lost species with each
reduction in area.
• Showed area has positive influence on species
richness.
Manipulating Island Area
Island Biogeography Update
• Brown and Kodric-Brown found higher
immigration rates to near islands can reduce
extinction rates.
• Lomolino found island area can have a
significant effect on immigration rates.
• Area and isolation are only two of several
environmental factors affect island species
richness.
Latitudinal Gradients in Species
Richness
• Most groups of organisms are more species-rich
in the tropics.
• Brown grouped hypotheses into six categories:
– Time Since Perturbation
• More species in the tropics because tropics are older and
disturbed less frequently.
– More time for speciation, and less frequent disturbance reduces
extinction rate.
Latitudinal Gradients in Species
Richness
– Productivity
• High productivity contributes to high species
richness.
– More energy to divide among population.
– Environmental Heterogeneity
• More heterogeneity, thus more potential habitat
areas and niches.
Latitudinal Gradients in Species
Richness
– Favorableness
• Tropics have more favorable environments.
– No extremes to limit diversity.
– Niche Breadth and Interspecific Interactions
• Various themes
– Brown suggests biological processes must play secondary role.
» Ultimate causes must by physical differences.
Area and Latitudinal Gradients
in Species Richness
• Rosenzweig proposed immigration can be
largely discounted at broad scales, thus
speciation will be primary source of new
species.
– Species removal via extinction.
• Tropics richness is greater due to higher rates of
speciation and / or lower rates of extinction.
Continental Area and Species
Richness
• Rosenzweig
found a strong
positive
relationship
between area
and species
diversity.