The Ecological Niche and Ecological Niche Modeling
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1 The Ecological Niche and Ecological Niche Modeling Tereza Jezkova School of Life Sciences, University of Nevada, Las Vegas Modified, T Kittel March 2012
Transcript of The Ecological Niche and Ecological Niche Modeling
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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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Historical - might do well somewhere but not there because of dispersal Biotic - predation etc Realized envir- what actually available Realized niche = Actual 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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all niche categories can change with time eg last glacial max (LGM) = environ changes Fundamental niche can also change - but this requires evolutionary shifts - can't predict. Can be adaptive (deterministic) or non-adaptive (e.g., bottlenecks; random: genetic drift)
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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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famous example of niche partitioning - experimental removal of 1 or other sp
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Niche partitioning and Law of Competitive Exclusion
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2 spp of Anolis - ~same size, same food types (smaller liz's) some islands -one goes extinct other islands - one eats small food another - one feeds in trees, other on ground
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Ecological niche modelingPurpose: ·
- Approximation of a Species Distribution
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use of Species Niche Modeling - to get better idea of species distribution - in case of incomplete field sampling --> where are ideal for a species, where might go look for the species
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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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blue area - ideal for species
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Ecological niche modelingPurpose: ·
- Species Diversity Analysis
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Overlap many models to get spp diversity
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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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projecting habitat distribution in GIS
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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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4th diagram: predict species distribution in time, e.g. past or future environmental conditions. -- How are these predictions made? In general, they use the methodology of ecological niche modeling. This methodology can be described in four steps. First, the researchers assemble occurrence records for the target species – coordinates where the species was documented as “present. Second, they assemble digital maps environmental variables that they suspect could be important in delimiting the species distribution – these environmental variable could be climate (tem and prec), also soils, vegetation, food resources, competition and so on. This simple example would represent temperature along elevation gradient or latitudinal gradient. In the third step, they delimitate suitable habitat based on the information learned from the occurrence records – the green rectangle represent the suitable niche for our hypothetical species. In the fourth step, the same environmental variables are obtained under a scenario of a climate change, in this case global warming, and the range shift is inferred. But this methodology makes one major assumption: What is it?______
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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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Problems models not perfect -- lot of things that can bias model results using the wrong / irrevant variable - e.g. winter air T vs. in burrows. no analog climate today in past/future
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sasquatch
blackbear
