Understanding Ecological Niches & Species Distributions: Modeling Fundamental & Realized N, Study notes of Climatology

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A gentle introduction to

modeling ecological niches

and species distributions

Different Definitions of Niche

 Many definitions. Key concepts:  Grinnelian niche – habitat requirements and characteristics that foster persistence  Eltonian niche – focused on communities and their trophic levels and interactions. Typically considered at local scales.  Hutichinsonian niche – Hutchinson considered niche as a n- dimensional hypervolume defining both environmental conditions and resources. Distinguished bet. fundamental and realized niche

 The full range of environmental conditions (biological and physical) under which an organism can exist describes its fundamental niche.

 Because of biotic interactions (competition, predation), the realized niche is almost always smaller.

Biotic Requirements

• Eltonian Niche
• Interactions with other species - Competition - Exploitation - Commensalism - Mutualism

Tolerance niche Fundamental niche

Fundamental niche intimately tied

to population/species

physiological tolerances

Movement

• Where originated
• Dispersal ability

Conceptual background

• Will focus on conceptual basis about what is being modeled in most correlative modeling approaches
• Before beginning: is there a difference between ”ecological niche modeling” and ”species distribution modeling”? - To model species distributions, it is critical to also model the niche - SDM also incorporates information about movement biology e.g. dispersal/colonization - This means we often are working in geographic space and environmental spaces and switching between them

The BAM Diagram: Alternative

Scenarios

For each unit of diversity (e.g. species) these overlaps are different (and hard to know apriori)

Occupied Distributional Area

(G O )

A∩B∩M

Potential Distributional Area

(G P )

G O ∪G I =G A ∩B

Switching from G-space (where

we have been) to E-space

η(G) η-1(Eʹ)

the multivariate space of environmental dimensions associated with G

the geographic location(s) that correspond to a given environmental combination E’

The fundamentals of modeling

the niche

N* F is the notation for the “existing fundamental niche”

and is often what is modeled in correlative approaches

N F ∩η(M)=^ N* F

N* F is thus a subset of the fundamental niche based on

conditions represented on real-world landscapes

Fundamentals

of Niche

Modeling

Mechanistic models: the Gold Standard?

• Experimentally-determined

physiological limits

• Response curves
  • Physiological performance
  • Mortality
  • Reproductive success
• Know full range of a species’

fundamental niche

Mechanistic models: the “but”

• Non-model organisms a pain - Access - Facilities