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