Interspecific competition and conceptual models Flashcards
What are the three main types of interaction between two species?
Mutualism (+/+), Competition (-/-), Exploitation (+/-)
Mutualism benefits both species, competition harms both due to resource limitations, and exploitation benefits one species while harming the other.
What is the first and simplest model of interspecific competition?
The Lotka-Volterra competition model.
What do the two interspecific competition coefficients in the Lotka-Volterra model express?
α12: The effect of species 2 on species 1
α21: The effect of species 1 on species 2
What are the four general outcomes of interspecific competition between two species?
Species 1 always wins
Species 2 always wins
Stable coexistence
Outcome depends on initial conditions (priority effect)
What do ecologists mean when they use the term ‘stable coexistence’?
A stable equilibrium where both species persist over time, defined by dN/dt = 0 for both species simultaneously.
Who is credited as being the author of the resource-ratio model of plant competition?
David Tilman
What is expressed by a zero net growth isocline (ZNGI) in Tilman’s model?
Line where population growth = 0
What is expressed by the resource supply point (RSP) in Tilman’s model?
Concentrations of resources in the environment before plants take them up.
What is expressed by the consumption vectors in Tilman’s model?
Rate and ratio at which species consume resources.
How are differences in environmental quality expressed in Tilman’s model?
Resource availability (N and P concentrations)
Species’ ability to deplete them
What is the meaning of R* in Tilman’s model?
The lowest resource level a species can sustain itself at.
How does R* relate to competitive outcomes?
Species with the lowest R* for a limiting resource will outcompete others.
What can be determined from a graphic representation of ZNGIs with RSP and consumption vectors?
If ZNGIs cross, coexistence is possible; if not, one species wins.
What is a conceptual limitation of Tilman’s model?
It assumes each species is limited by a single resource.
What are the three principal plant strategies in Grime’s triangle?
Competitors (C) → Productive environments with low stress/disturbance
Ruderals (R) → Disturbed environments
Stress-tolerators (S) → Harsh environments with low productivity
How do Tilman and Grime differ in their descriptions of environmental characteristics?
Tilman: Environment defined by resource availability and species depletion
Grime: Environment defined by stress, disturbance, and competition
Who is credited as the author of the centrifugal organization hypothesis?
Paul Keddy
What biome inspired Keddy’s centrifugal organization hypothesis?
Coastal wetlands
What species inhabit the core habitat and satellite habitats in Keddy’s model?
Core habitat: Competitive species
Satellite (peripheral) habitats: Tolerance specialists
What is the role of abiotic and biotic filters in determining species presence?
Abiotic filter: Determines species tolerance to environmental conditions
Biotic filter: Determines which species can coexist with others
What is the role of disturbance in spatial models of coexistence?
Disturbance creates open patches where new species can establish themselves, promoting coexistence.
What is a fugitive species in spatial models of coexistence?
A species that thrives in disturbed environments but is outcompeted in stable ones.
What key factor allows coexistence in the lottery model of coexistence?
Disturbance, which periodically opens new patches for colonization.
What key trait allows coexistence in the lottery model of coexistence?
Dispersal ability, which allows species to colonize open patches after disturbance.
How does Chesson differentiate between stabilizing and equalizing effects on competitive coexistence?
Equalizing effects: Diminish fitness differences between species
Stabilizing effects: Involve fitness trade-offs between species
Who is credited as the author of the Neutral Model of plant coexistence?
Stephen Hubbell
What habitat inspired Hubbell’s Neutral Model?
Tropical rainforests
What assumption distinguishes Hubbell’s model from all other models of plant coexistence?
Species are functionally equivalent (no competitive differences).
What processes maintain the number of species in a community in the Neutral Model?
Random drift
Dispersal
Speciation
