Chapter 14: Interspecific Competition Flashcards
Interspecific competition?
- competition between two different species for a common resource in short supply
Interspecific competition is probably a major force behind?
- species divergence and specialization
Competition ?
- any relationship in which populations of two or more species negatively affected
What are six types of competition?
- Consumption of shared resources
- Preemption of space(primarily between sessile organisms aka since I’m taking u[ this space its not available to anyone else)
- Overgrowth: growing on top of another species etc like lichens
- Chemical interaction: toxins or growth inhibitors (common in forests where a tree lays dead needles on ground)
- Territorial: behavioural exclusion from space defended as territory
- Encounter: non territorial meetings e.g. scavengers fighting over carcass
Competition models?
- mathematical models used to build hypotheses about species interactions
Classic competition model?
- Lotka-Volterra Model based on the logistic equation from chapter 11
Logistic equation?
dN/dt= rN( K-N/K)
*k= carrying capacity
Lotka-volterra model formula?
- term added for competitive effect of one species on the population growth of another
Species 1: dN1/dt= r1N1(K1-N1- alphaN2/K1)
Species2: dN2/dt= r2N2( K2-N2-betaN1/K2)
*alpha is the competitive effect of species 2 on species 1; beta is the competitive effect of species 1 on species 2
Lotka-volterra model:
-Amount of resource used by two species is not/ or is usually the same
- is not
Lotka-volterra model:
-convert from one species to another?
- alpha N2 is the number of equivalents of species 1
- beta N1 is the number of equivalents of species 2
- can convert between species suing coefficient
- can confer that epopulation density of one species to the equivalent of another
Lotka-volterra model:
- explain the alpha value system
- alpha= 0 species 2 has no competitive effect on species 1
- alpha 1, species 2 individual more effect than a species 1 individual
Lotka-volterra model:
- without interspecific competition whats going on with K?
- without interspecific competition (if alpha or N2= 0 or beta or N1 = 0), population of each species grows logistically to K
Lotka-volterra model:
- with interspecific competition what occurs?
- either one species out competes the other or they coexist
Lotka-volterra model:
- how many situations does it predict?
4
Lotka-volterra model:
- graphical models?
- Zero growth isoclines points at which population growths 0 (dN1/dt and dN2/dt= 0_
- two diagonal lines are plotted one for each species
- populations always come back to zero growth isocline
Lotka-volterra model:
- outcomes?
L>winning?
- Species 1 wins: even when species 2 is at its carrying capacity, it can’t stop species 1 from increasing ( K2<K1/alpha)
- Species 2: reverse situation
- when species 2 wins its isocline is now higher than species 1
Lotka-volterra model:
- equilibrium outcomes?
- Unstable equilibrium: determined by initial densities. Interspecific competition limits growth more than infraspecific (outcome can go either way via one winning)
- Stable equilibrium: intraspecific competition limits population growth more than interspecific
( coexistence?)
- 4 Competitive Exclusion Principle:
- explain this principle
- complex competitors cannot coexist
- when two species have same ecological requirements and live in the same space, the species with faster population growth expected to dried the other to extinction
- 4 Competitive Exclusion Principle:
- explain assumptions
- assumes same resource requirements and environment is constant
- not likely in nature (aka not likely they will have the exact same resources) **resources are not the only regulation of a population
14.5 Effect of Factors other than resources ?
- e.g. plant growth also affected by temperature, pH, rekatuve humidity, salinity
- *biotic and abioitc interactions influencing whether species A over Species B occurs as well not just the two species interaction.
14.6 Temporal Variation in environment??
- ex: shift in grass species in grasslands in zimbabwe
- associated with changes in annual rainuful
- you should factor in different seasons
- when rainfall was low the green species dominant but as soon as it increased another species displaced it
- whole environmental conditions can change and affect a species
- 7 Competition Occurs for Multiple Resources:
- Example via Groves and Williams 1975
- competition between clover and skelton weed
- clover better competitor for both above and below structural resources
- one species does not do well when just the roots are completing
- when just the shoots are in comp each other the same species does not do well
- when fully exposed to each other the same species did not do well at well.
14.8 Relative competitive abilities change along environmental gradients ?
- due to changes in carrying capacities of species related to changing resources base or form changes in the physics environment that interact with resource availability
- *competition changes as you go along the gradient
ex: salt marsh zonation - combo of both biological and environmental factors
14.10 Resource petitioning also important in coexistence ??
-animals use different kinds and sizes of food at different times or forage in different areas
ex: size of canine teeth (and prey) of cats..
*one species forages in morning and the another light.
example : size of canine teeth which relates to different types of prey they can exploit…therefore coexisting cat species presumedly are not competing for the same resources
- 10 Resource petitioning also important in coexistence ??
- plants species vary in?
- proportions of nutrients required, tolerance for light and shade.
- two plants side by side may have different root systems one allowing them to grow deeper down and another to grow deep down.
Demonstrating the importance of competition in the field?
- competition is difficult to demonstrate in the field.
* *you cannot control a lot of factors in the field…lots of confounding variables due to environment changes..
Demonstrating the importance of competition in the field?
-techniques?
- cage animals in our out separating predators
L> still simplistic bc what is the affect the changes has on everything else
**its hard to tie in alb results in nature for exploiting
