Post on 15-Mar-2020
transcript
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The Ecological Niche and Ecological Niche Modeling
Tereza JezkovaSchool of Life Sciences, University of Nevada, Las Vegas
Modified, T KittelMarch 2012
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What drives species distributions?
•All species have tolerance limits for environmental factors beyond which individuals cannot survive, grow, or reproduce
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Environmental Gradient
Tolerance Limits and Optimum Range
Tolerance limits exist for all important environmental factors
Tolerance Limits
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Critical factors and Tolerance Limits
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• For some species, one factor may be most important in regulating a species’ distribution and abundance.
Critical factors and Tolerance Limits
• Usually, many factors interact to limit species distribution.
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Critical factors and Tolerance Limits
• Organism may have a wide range of tolerance to some factors and a narrow range to other factors
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FUNDAMENTAL NICHE
Historical factors
Biotic factors
Realized environment
REALIZED NICHE
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Tolerance Limits and Optimum Range Fundamental versus realized niche
Fundamental (theoretical) niche - is the full spectrum of environmental factors that can be potentially utilized by an organism
Realized (actual) niche - represent a subset of a fundamental niche that the organism can actually utilize restricted by:
- historical factors (dispersal limitations)- biotic factors (competitors, predators)- realized environment (existent conditions)
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Tolerance Limits and Optimum Range Niche shiftAre niches stable?
Realized niche shifts all the time due to •changing biotic interactions, •realized environment, •time to disperse
Time T1 Time T2
RealizedNicheShift
NO!
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FundamentalNicheShift
•Fundamental niche shift when tolerance limits change due to EVOLUTIONARY ADAPTATION
Time T1 Time T2
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Resource Partitioning
• Law of Competitive Exclusion - No two species will occupy the same niche and compete for exactly the same resources
- Extinction of one of them- Niche Partitioning (spatial, temporal)
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Niche partitioning and Law of Competitive Exclusion
Balanus
Balanus
Chthamalus
Chthamalus
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Niche partitioning and Law of Competitive Exclusion
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Ecological niche modelingPurpose: ·
- Approximation of a Species Distribution
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Ecological niche modelingPurpose: ·
- Potential Niche Habitat Modeling (Invasive species, diseases)
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Ecological niche modelingPurpose: ·
- Site Selection or conservation priority: Suitability Analysis
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Ecological niche modelingPurpose: ·
- Species Diversity Analysis
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Ecological niche modelingTwo types:
1. DEDUCTIVE: A priori knowledge about the organismExample: SWReGAP http://fws-nmcfwru.nmsu.edu/swregap/habitatreview/
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Ecological niche modelingTwo types:2. CORRELATIVE: Self-learning algorithms based on known occurrence records and a set of environmental variables
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Occurrence records:
- Own surveys (small scale)- Digital Databases (e.g. museum specimens)
MANIS (mammals)ORNIS (birds)HERPNET (reptiles)
HAVE TO BE GEOREFERENCED (must have coordinates)
http://manisnet.org/http://olla.berkeley.edu/ornisnet/http://www.herpnet.org/
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WORLDCLIM http://worldclim.org/
Variables: • Temperature (monthly) • Precipitation (monthly)•19 Bioclimatic variables• Current, Future, Past
Resolution:• ca. 1, 5, 10 km
Coverage• World
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Southwest Regional Gap Analysis Project http://earth.gis.usu.edu/swgapNorthwest GAP Analysis Project http://gap.uidaho.edu/index.php/gap-home/Northwest- GAP
Variables: • Landcover
Resolution:• ca. 30 m
Coverage• western states
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Natural Resources Conservation Service (NRCS)SSURGO Soil Data http://soils.usda.gov/survey/geography/ssurgo/
Variables: • Soils
Resolution:• ca. 30 m
Coverage• USA but incomplete
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Ecological niche modeling
Step 1: occurrence records
Step 2: environmental variables
Step 3: current ecological niche
Step 4: projected ecological niche
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Ecological niche modeling – models from Maxent
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Problems: Models are only as good as the data that goes into it!!!
Calibration of Models• Insufficient or biased occurrence records• Insufficient or meaningless environmental variables
Projection-Source Model• Inaccuracies in climate reconstructions• Dispersal limitations• Non-analogous climates• Niche shift (evolution)
!!! WRONG INTERPRETATIONS !!!
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sasquatch
blackbear