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
