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The BAM Diagram: A Useful Heuristic
A. Townsend PetersonUniversity of Kansas
Charles Elton – niche as role in communities
G. Evelyn Hutchinson – multidimensional ecological niches,
bionomic versus scenopoetic variables
GEOGRAPHY – THE DISTRIBUTION
The Area of Distribution
G Physiological requirements
(Abiotic)
A
Favorable bioticenvironment
(Biotic)B
Accessible to dispersal(Movements)
M
The A and B Circles
• Physiological requirements
• Non-reactive variables. Uncoupled
• Roughly independent of the interactions
• Low “resolution”
• Biotic requirements and impacts. Resource consumption, interactions, competitors, predators...
• Variables interactive, dynamically coupled
• High resolution
A B
A Useful and Forgotten Distinction of Hutchinson (1978)
• Scenopoetic variables. Non-interacting, slowly changing from a species point of view. Define conditions
• Bionomic variables. Coupled, fast changing. Define regulation
• Hutchinson´s useful distinction was quickly forgotten and then reinvented by Austin, Begon, Jackson & Overpeck, Meszena and others.
M = Barriers
Abiotic niche
Biotic interactionsAccessibility
Classic BAM Configuration
Abiotic niche
Biotic interactionsAccessibility
Biotic interactions
Accessibility
Abiotic nicheHow HutchinsonSaw the World
Hutchinson needs to get
out and travel a bit!
Abiotic niche
Biotic interactionsAccessibility
Abiotic niche
Biotic interactions
Accessibility
Wallace’s World
Demonstration of M Effects
• Clear demonstration of the importance of dispersal limitation on species’ distributions
• Invasive species – originally confined to a native distributional area
• Some transport (often human-mediated) expands M
• Distribution expands accordingly
Abiotic niche
Biotic interactionsAccessibility
Area presenting appropriate combinations of abiotic and biotic conditions (= potential distribution)
Actual geographic distribution(abiotic and biotic conditions fulfilled,accessible to dispersers)
Aedes albopictus
• Known as the “Asian Tiger Mosquito”
• Invader; fastest spreading mosquito in the world
• Aggressive daytime biter and pest
• Known to transmit Dengue, La Crosse, St. Louis, Eastern Equine, Ross River, Rift Valley, and West Nile Viruses
Aedes albopictus
Present predicted distribution, native range in Asia
Aedes albopictus:USA invasion
Projected Asian niche into USA present to create invasion risk-map. How well did GARP perform...
Aedes albopictus: USA invasion
Aedes albopictus: world risk-map
Abiotic niche
Biotic interactionsAccessibility
BAM and Eltonian Noise
Abiotic niche
Biotic interactions
Accessibility
ENVIRONMENT
Five Goals of Niche Modeling?
1. ESTIMATE THE FUNDAMENTAL NICHE2. ESTIMATE THE FUNDAMENTAL NICHE3. ESTIMATE THE FUNDAMENTAL NICHE4. ESTIMATE THE FUNDAMENTAL NICHE5. ESTIMATE THE FUNDAMENTAL NICHE
How Would the Fundamental Niche Look?
• In any one dimension, expected to be unimodal
• In multiple dimensions, expected to be convex• So, simple models are probably better• Need to take sampling and incomplete
representation into account carefully
http://d1vn86fw4xmcz1.cloudfront.net/content/royptb/367/1596/1665/F1.large.jpg
The Area of Distribution
G Physiological requirements
(Abiotic)
A
Favorable bioticenvironment
(Biotic)B
Accessible to dispersal(Movements)
M
Fundamental niche
Existing fundamental
niche
Realized ecological
niche
Can EVOLVE Will change with any
range difference
?
?
SUMMARY
Assess levels of spatial autocorrelation in environmental data, adjust input point data accordingly
Estimate ecological niche (various algorithms)
Evaluation reality of model transfer results, when possible
Transfer to other situations—time and space
Project niche model to geographic space
Model calibration, adjusting parameters to maximize quality
Collate primary biodiversity data documenting occurrences
Process environmental layers to be maximally relevant to distributional ecology of species in question
Collate GIS database of relevant environmental data layers
Assess BAM scenario for species in question; avoid M-limited situations
Saupe et al. 2012. Variation in niche and distribution model performance: The need for a priori assessment of key causal factors. Ecological Modelling, 237–238, 11-22.
Estimate M as area of analysis in study
Barve et al. 2011. The crucial role of the accessible area in ecological niche modeling and species distribution modeling. Ecological Modelling, 222, 1810-1819.
Assess extrapolation (MESS and MOP)
KU Ecological Niche Modeling Group. 2013. Constraints on interpretation of ecological niche models by limited environmental ranges on calibration areas. In preparation.
Model evaluationPeterson et al. 2008. Rethinking receiver operating characteristic analysis applications in ecological niche modelling. Ecological Modelling, 213, 63-72.
Model thresholdingPeterson et al. 2007. Transferability and model evaluation in ecological niche modeling: A comparison of GARP and Maxent. Ecography, 30, 550-560.
Assess spatial precision of occurrence data, adjust inclusion of data (obs and env) accordingly
General Methodological Summary: Peterson et al. (2011) Ecological Niches and Geographic Distributions, Princeton University Press, Princeton.
Refine estimate of current distribution via land use, etc.
Reduce dimensionality
Compare present and future to assess effects of change