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

town@ku.edu