Ecological theory of evolution 3 Flashcards
(19 cards)
What is competition?
Crawley: an interaction that leads to an increase in one specie’s population density and to a decrease in the per capita growth rate and population density in another.
Begon
an interaction between individuals, brought about by a shared requirement for a resource in limited supply, and leading to a reduction in the survivorship, growth and/or the reproduction of at least some of the individuals concerned.
Describe consumptive competition
When organisms compete for the same resource. E.g. trees for nitrogen and other nutrients
Describe overgrowth compeition
When an organism grows over another, blocking access to resources
Describe chemical competition
occurs when one species produces toxins that negatively affect another. Note how few plants are growing under these Salvia shrubs.
Describe territorial competition
occurs when mobile organisms protect a feeding or breeding territory.
Describe encounter compeition
When organisms interefere directly with each others access to specific resources
What is exploitation compeition
One species directly inhibits the foraging, survival or reproduction of another through competition for resources or space
What is interference competition?
One species directly inhibits the foraging, survival or reproduction of another
What is preemptive competition?
A competitor recruits to and dominates a habitat, monopolosing all available space
Intra specific vs inter specific
Intra occurs between individuals of the same species
Inter occurs between individuals belonging to different species
Describe ecological niche
Hutchinson
Niche can be viewed as an imaginary space with many dimensions, in which each dimension or axis represents the range of some environmental condition or resource that is required by the species.
Fundamental niche = the total range of environmental conditions that are suitable for a particular species ti exist on its own
Realised niche = describes that part of the fundamental niche actually occupied by the species
Describe coexistence
Partial niche overlap can lead to niche partitioning and adaptive radiation, and competitive exclusion
Describe competitive exclusion
Hardin
Complete competitors cannot exist. Species cannot coexist if they require the same limiting resource
+ Gause’s model
Describe the chemostat
Constant volume in the culture flask -> single resource is brougt in and a fraction of the liquid is taken out. Culture flask is shaken so no spatial structure
Describe the theory of the chemostat
The rate of change of resource concentration = input - resource consumption by different consumerrs - dilution
The rate of change of population density = growth due to resource consumption - dilution
General condition: Coexistence is not possible and the strain that can survive on the lowest concentration of the resource will always out-compete all others
How is diversity maintained in the chemostat?
product inhibition
temporal resource heterogeneity
cross-feeding
Describe product inhibition
N1 and N2 share resource. Inhbitor on N2
N2 can grow on the lowest amount of resources and therefore will outcompete N1. But in the presence of a substance that inhibits N2, both competitors coexist
Experimental tests where diversity maintained in yeast
Short-term competition = competitive exclusion
However: theory of the chemostat contains only ecological interactions.
Short-term compeitions cannot always predict long-term maintenance of diversity
Sharing of a niche is a evolutionary strategy.
Survival of the fittest and flattest
Fit = fast growers
Flat = robust to mutation
