EE 5- Interspecific Competition

These vocabulary flashcards cover the levels of biological organization and Tilman's Resource-Based Competition Models, focusing on R*, ZNGIs, and the conditions for coexistence as described in the lecture.

Organism

A level of organization where various organ systems work together in a functional unit.

Population

A group consisting of organisms of the same species.

Community

The populations of different species that populate the same area.

Ecosystem

A community together with the nonliving environment.

Biosphere

The combination of Earth and all of its communities.

Interspecific competition

An interaction where two different populations (e.g., cat and dog) have a negative impact on each other.

Asterionella

A phytoplankton species that can drive Cyclotella to extinction due to resource competition for phosphorus.

Cyclotella

A phytoplankton species that is outcompeted when phosphorus is the limiting resource in competition with Asterionella.

$$R^*$$

The equilibrium resource availability at which reproduction and mortality are balanced, and the level to which a species can reduce resources in the environment.

Tilman’s Resource-Based Competition Models

A framework used to predict the likelihood of species coexistence based on their resource needs and impacts.

Non renewable resource dynamics

A resource model where the resource level decreases over time from Time 1 to Time 4 without replenishment.

Completely renewable resource dynamics

A resource model where the resource level returns to a higher state over time after being used.

Constant rate resource dynamics

A model where the resource is supplied at a steady rate, and at equilibrium, consumption balances supply.

Resource supply point

A characteristic of the environment that measures the total amount of resource available, whether bound in organisms or in the environment.

Impact vectors

Arrows that show the direction a population is influencing a resource based on the ratio of resources needed to be sustained.

Per capita birth rate

In Tilman's model, this factor is treated as a function of resource availability, $\text{R}$.

Mortality rate ($m_A$)

A parameter in resource competition models assumed to remain constant even as resource availability changes.

Competitive exclusion principle (One resource)

When two species compete for one limiting resource, the species with the lower $R^*$ deterministically outcompetes the other.

Zero Net Growth Isocline (ZNGI)

A boundary line in a resource graph where $\frac{dN}{dt} = 0$, dividing the region into zones favoring growth or decline.

Upper right zone (ZNGI)

The area on a resource plot above the Zero Net Growth Isocline that favors population growth.

Outer zone (ZNGI)

The area on a resource plot below the Zero Net Growth Isocline that favors population decline.

Equilibrium point

The state where consumer impact balances resource supply, occurring where the supply of resources is equal and opposite to the species impact.

Essential resources

Two resources (e.g., $R_1$ and $R_2$) where growth is limited if the level of either resource falls below the required threshold.

Trade-offs

Constraints on species traits where improvements in one area (e.g., root allocation) come at the expense of another (e.g., leaf allocation).

Physiological Trade-off example

The contrast between a Marathon Runner (Speed & Endurance) and a Sumo Wrestler (Weight & Strength).

Allocation Trade-off

The trade-off where investment in leaves for light capture occurs at the expense of nutrient sequestration from soil via roots.

Stable Tradeoff Indicator

Represented by intersecting Zero Net Growth Isoclines in a two-resource model.

Coexistence Condition

Occurs specifically when species compete more strongly with themselves (intraspecific) than with their competitor (interspecific).

Zone 1 (Habitat)

A region in the resource model where resource supply is so low that neither competing species can persist, leading to extinction for both.

Zone 4 (Habitat)

A region in the resource model where coexistence is possible because species become self-limiting before they can impact the other.

Self-limiting

A condition in Zone 4 where Species A consumes more of the resource that limits its own growth (Resource 2) and Species B consumes more of Resource 1.

Multispecies model limitation

At equilibrium under these models, no more species can coexist than there are limiting resources.

Maximum equilibrium coexistence

In a system with exactly two limiting resources, a maximum of two species can coexist.

Unstable outcome in Zone 4

If impact vectors are switched such that species consume more of the resource that limits their competitor, the outcome depends on initial density and one species drives the other extinct.

Phosphate and Silica

The two specific resources used by Aimar Rakko to demonstrate Zero Net Growth Isoclines in Tilman's theory.