Slideshow 9 Flashcards
What is interspecific competition
is the interaction occurring between species when
increased abundance of a first species causes the population growth of a second to decrease, Interspecific competition between two species occurs when individuals of one
species suffer a reduction in growth rate from a second species due to their
shared use of limiting resources (exploitative competition) or active
interference (interference competition)
What are the two types of Interspecific competition
Exploitative competition and Interference competition
What is Exploitative competition
occurs when a species consumes a shared
resource that limits its and other species population growth (resource is less available to
other species)
What is Interference competition
occurs when individuals of one species
restricts another species access to a limiting resource (e.g. territorial defense) or it may
simple involve occupying a space that excludes another
What is the formula for the lotka voltera model when adding density dependent effects
dN1/dt=r1N1(K1-N1/K1)
or
dN2/dt=r2N2(K2-N2/K2)
Where:
N1 and N2 are the densities of species 1 and 2 respectively
r1 and r2 – are their (species 1 and 2) intrinsic growth rates
K1 and K2 are their (species 1 and 2) carrying capacities
How should the Lotka-Volterra model be changed for INTERSPECIFIC COMPETITION
(i) A term for the density of the competing species
(ii) Multiplied the density term by a constant
“the competition coefficient”
What does the lotka volterra model not tell us about interspecfic compettion
does NOT specific the mechanism of
competition between the species
What needs to be added to the lotka voltera model for interspecific competiton
(i) Density of species 2
(ii) The competition coefficient (constant)
What is the formula for the lotka Volterra model with interspecific competition
dN1/dt=r1N1(K1-N1- alpha12N2/K1)
or
dN2/dt=r2N2(K2-N2-alpha21N1/K2)
What is the competition coefficent
alpha
is the effect of an individual of species 2 on the per capita
growth rate of species 1 relative to the effect of an individual of 1 on its own per capita
growth rate (and vice versa)
How do you calculate the alpha coefficient value
IF we assume one elk is equivalent to 3 deer.
THUS alpha12 = 1/3 = 0.33
Alpha21 – this is effect of species one on species two
THUS alpha21 = 3/1 = 3
Not always reciprocal……
What does the intersect of 2 isoclines represent
Both species are in equilibrium
What happens when the tragectories arrows for both populations point away from the equilibrium point
Unstable
What happens when the tragectories arrows for both populations pointto from the equilibrium point
Stable
Is linear competition in nature likely
it is unlikely
What is the Theta logistic model
Proposed to model non linear competition
What is the Theta logistic model formula
dNi/dt = riNi(1-(Ni/Ki)^theta -alphaij (Nj/Ki))
What is the multi species MATRIX format
K = AN*
This approach commonly used by THEORISTS to examine the effects of interspecific
Competition on questions over COMMUNITY STABILITY, INVASIBILITY and THE
EQUILIBIRUM NUMBER of COEXISTING SPECIES
N* = column vector of the species’ equilibrium densities
A = square matrix of the interaction coefficients
Application of community matrices to natural systems is RARE
CONSUMER-RESOURCE MODELS of COMPETITION
1) Incorporates how competing consumers affect their resources and;
2) How consumer population growth rates are in turn affected by resource densities
What is a resource
A resource is any substance or factor which can lead to increased population
growth rates as its availability in the environment is increased and which is consumed by
an organism
Resources are entities which contribute positively to population growth and are
consumed in the process
What are the two properties that define a resource
(1) A resource contributes positively to the growth rate of the consumer population
(2) A resource is consumed and is thus made unavailable to other individuals or species
What does r* value mean in CONSUMER-RESOURCE MODELS of COMPETITION
the minimum equilibrium resource requirement needed to maintain a
consumer population experiencing a given mortality rate (m)
If we assume the consumer population experiences some per capita density-
What is the POPULATION DYNAMICS of ONE CONSUMER:
If a consumer is introduced to an environment with mortality rate m and R > R, the
consumer population will increase over time AND the abundance of the resource will decline
Eventually reaching R
in a Two consumers competing for one resourceWhat population grows faster
grows faster because at high
resource levels its net rate of population growth (birth
rate minus mortality) is higher.
Coexistence on a single, fluctuating resource. what species will win
species with the lowest R* value
What is a ESSENTIAL RESOURCES
required for growth and one essential resource cannot substitute for
another
What is a SUBSTITUTABLE RESOURCES:
where one resource can be replaced by another
FOR essential resources, where is equilibrium at
at all points
on the L-shape
