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Population and Community Ecology > Competition > Flashcards

Flashcards in Competition Deck (33):
1

What is competitions effect on sp 1 and sp 2?

Both negative

2

What is competition?

Interactions in which two species negatively influence each other’s population growth rates

3

3 types of competition?

Exploitation competition
Compete for a shared resource

Interference competition
Behaviour that reduces resource exploitation by other individuals/species

Pre-emptive competition
Compete for limited space
Barnacles on rocks

4

Interspecific and infraspecific competition.

Intraspecific competition:
Among individuals within a population
Captured by models with density-dependence (e.g., logistic)

Interspecific competition
Among individuals of different species
Population growth is affect by other species’ population size
(e.g. Lotka-Volterra)

5

Whats competition coefficients?

-Apha
-How much each individual of species 2 reduces carrying capacity of species 1

6

Which colour box is sp 1 and sp2?

-Red box:
species 1 individual (size = 1)
-Blue box:
species 2 individual (size = α12)

7

Whats the frame?

carrying capacity 
of species 1

8

What does more individuals of N2 result in?

Less N1 at equilibrium

9

What does a larger alpha result in?

Steeper growth isocline

10

What are the 4 possible outcomes?

-Sp2 win- N2 isocline above N1
-Sp1 win- N1 isocline above N2
-Co existence- N1 K below N2 on x axis and N2 K below N1 on y axis
-Founder control (unstable)
N1 K above N2 on x axis and N2 K above N1 on y axis

11

How to be a successful competitor?

-Achieve positive growth when competitor at K
-More efficient at exploiting resources
-Lessen effect of competition

12

What does stable coexistence require?

Both species can invade one another

13

Criticisms of Lotka-Volterra competition

Unclear “how” species compete
→ what they are competing for?

α only measure pair-wise competition, not among >2 species (“higher-order interactions”)

Hard to measure parameters

Predictions only confirmed in simple lab experiments

14

“Resource competition” theory

Predicts what species wins without observing them together

15

What s a resource?

-Something in the environment that
(1) contributes positively to population growth, and
(2) is consumed in the process

-Examples: Light, nutrients, food
Not examples: Temperature, air

16

Assume per-capita biomass growth depends on what?

The concentration of some resource R

17

What is stable competition equilibrium?

If R < R*, then B(biomass) ↓, consumption ↓, and R ↑

18

What happens when biomass increases?

R is reduced to lowest R*

19

Whats an example of competition for a single resource?

2 species of diatoms (algae) competing for Si

20

Where is the optimum Growth os Species?

Where the growth rate intersects the R*

21

What happens when there are two resources?

Resources not substitutable
Positive growth only if
R1 > R1*
and
R2 > R2*

22

What happens when neither R is < R*?

Species at equilibrium

23

Whats the consumption vector?

(c)
Relative rate at which species consumes R1 and R2
Points in direction from (R1*,R2*) to origin

24

Whats the supply point?

(S): Total amount of R1, R2 that can exist in the environment (without consumption)

25

Whats the supply vector?

(U): Rate of resource replenishment
Points from current (R1,R2) back to S

26

Whats ZNGI?

Zero net growth isocline

27

What happens if S is below ZNGI?

Species can't persist

28

What happens if S is above ZNGI

-Species can persist
-Equilibrium occurs along ZNGI where consumption vector is opposite supply vector (c = -U)
-Resource that is at R* at this point is the most limiting

29

What does the competition of 2 sp with 2 resources depend on? Which sp will win if they don't cross?

-The zero net growth isocline
-Species with lower R will win

30

What happens if ZNGI cross?

-Outcome depends on consumption vectors and supply point
- S before any isocline- both go extinct
- S infront of sp 1 isocline- sp 1 wins
- S infront of sp 2 isocline- sp 2 wins
-S infront of both (directly infront of sp 2)- Sp 1 wins
-S infront of both (directly infront of sp 2)- Sp 2 wins

31

Why is coexistence possible?

-Species 2 consumes more of, and is limited by, R1
-Species 1 consumes more of, and is limited by, R2
-Stronger competition with themselves than each other

32

How many species can persist with one resource? 2?

One
Two

33

When is coexistence possible?

Co-existence possible when:
1. Each species can survive on less of one resource than the other species
2. Environment provides adequate supply of both resources
3. Each species consumes more of the resource that is limiting to it