University of Vermont NR 2030 Exam 2 Questions With
Complete Solutions
Four outcomes of Lotka Volterra model
(a)species 1 competitively excludes species 2;
(b) species 2 competitively excludes species 1;
(c) either species wins based on population densities; or
(d) coexistence occurs.
competitive exclusion principle
proposes that two species competing for the same limited
resource cannot coexist, the better competitor will drive the
other to extinction
Interference competition
Direct, physical interference for limiting resources
exploitative competition
Indirect competition through reduction of resource pool
Apparent competition
Negative indirect interactions between species that arise because
they share a natural predator
What do species compete for?
Space, Light, Nutrients, Habitat, Competition for
The Portal Project
, Rodents vs. ants experiment:
(1) Wire mesh fence excluded rodents.
(2) Ants were excluded with insecticides.
(3) Both rodents and ants excluded.
(4) Undisturbed control plots.
Replication: 2 plots of each
The Portal Project results
(1) Rodents vs. ants: Competition asymmetry,
(2) Rodents were excluded, ant colonies increased by 71%.
(3) Ants were excluded, rodents increased in both number and
biomass (20 to 29%).
(4) Both rodents and ants were excluded, seeds increased by
450%.
How does a null model work?
A typical null model generates communities expected to occur
in the absence of a particular mechanism. Patterns generated
when you randomize all the data (i.e., invented communities) are
then compared statistically to patterns in the real community.
Null models can tell you about whether competition really
occurs and whether it matters.
Modern coexistence theory
spatial and temporal heterogeneity in the environment, in
conjunction with species differences in resource use (niche
differences and trade- offs) provide important general
coexistence mechanisms. Theory also shows that stable species
Complete Solutions
Four outcomes of Lotka Volterra model
(a)species 1 competitively excludes species 2;
(b) species 2 competitively excludes species 1;
(c) either species wins based on population densities; or
(d) coexistence occurs.
competitive exclusion principle
proposes that two species competing for the same limited
resource cannot coexist, the better competitor will drive the
other to extinction
Interference competition
Direct, physical interference for limiting resources
exploitative competition
Indirect competition through reduction of resource pool
Apparent competition
Negative indirect interactions between species that arise because
they share a natural predator
What do species compete for?
Space, Light, Nutrients, Habitat, Competition for
The Portal Project
, Rodents vs. ants experiment:
(1) Wire mesh fence excluded rodents.
(2) Ants were excluded with insecticides.
(3) Both rodents and ants excluded.
(4) Undisturbed control plots.
Replication: 2 plots of each
The Portal Project results
(1) Rodents vs. ants: Competition asymmetry,
(2) Rodents were excluded, ant colonies increased by 71%.
(3) Ants were excluded, rodents increased in both number and
biomass (20 to 29%).
(4) Both rodents and ants were excluded, seeds increased by
450%.
How does a null model work?
A typical null model generates communities expected to occur
in the absence of a particular mechanism. Patterns generated
when you randomize all the data (i.e., invented communities) are
then compared statistically to patterns in the real community.
Null models can tell you about whether competition really
occurs and whether it matters.
Modern coexistence theory
spatial and temporal heterogeneity in the environment, in
conjunction with species differences in resource use (niche
differences and trade- offs) provide important general
coexistence mechanisms. Theory also shows that stable species
