cbg 4- Interspecific Competition and Tilman's Resource-Based Models

This set of flashcards covers vocabulary and major concepts from Peter Graystock's lecture on interspecific competition and Tilman's resource-based models, including ZNGIs, R* values, and coexistence theories.

Population

A group consisting of organisms of the same species.

Community

Populations of different species that populate the same area.

Ecosystem

A community together with the nonliving environment.

Biosphere

The Earth and all of its communities.

$$R^*$$

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

Tilman’s Resource-Based Competition Models

A framework used to predict the outcomes of competition between populations based on their resource usage and requirements.

Zero Net Growth Isocline (ZNGI)

The boundary on a resource graph where the population growth rate is exactly zero ($dN/dt = 0$); levels above this line favor growth, while levels below it favor decline.

Resource Supply Point

A measure of the total amount of resource in an environment, which is a characteristic of the environment itself.

Impact Vectors

Arrows that show the direction and magnitude in which a population is influencing or consuming the resource availability.

Interspecific Competition

A competitive interaction between different species that typically has a negative impact on both populations in the framework of resource competition.

Intraspecific Competition

Competition occurring between members of the same species.

Lower $R^*$ Rule

When two species compete for one limiting resource, the species that can maintain positive growth on the lowest ration of resource will deterministically outcompete the other.

Physiological Trade-off

A constraint where improving one trait, such as speed, comes at the expense of another trait, such as strength, as seen in the comparison between a marathon runner and a sumo wrestler.

Allocation Trade-off

A botanical constraint where the investment of resources into leaves for light capture occurs at the expense of root development for nutrient sequestration from soil.

Essential Resources

Resources, such as $R_1$ and $R_2$, where a species requires both to sustain growth, and the omission of one leads to a population decline.

Asterionella

A phytoplankton species that, in resource competition experiments, was shown to drive Cyclotella to extinction when Phosphorus was the limiting resource.

Resource Supply Rate

The rate at which resources are added to the system; at equilibrium, this rate must be equal and opposite to the consumer impact rate.

Coexistence Requirement

For coexistence to be possible, species must compete more strongly with themselves (intraspecific) than with their competitor (interspecific).

Self-limiting

A state where a species consumes more of the resource that most limits its own growth, allowing for stable coexistence with a competitor.

Non-renewable Resource

A resource that is not naturally replenished over time within the context of the specific resource dynamics model.

Renewable Resource

A resource that replenishes itself over time in the environment, following specific supply dynamics.

Equilibrium Point

The specific resource levels where consumer impact balances resource supply, which depends on the location of the resource supply point.

Multispecies Competition Limit

Tilman's model predicts that at equilibrium, no more species can coexist than there are limiting resources.

Stable Trade-off

Indicated by intersecting Zero Net Growth Isoclines where one species is better at utilizing one resource while the other species is better at utilizing a second resource.

Zone 1 (Extinction Zone)

A region in a resource competition graph where resource levels are below the ZNGIs for all species, leading to total extinction.

Zone 4 (Coexistence Zone)

A region where species can coexist because they become self-limiting before they can drive their competitor to extinction.

Initial Conditions

Factors like initial population density that can determine the winner in unstable competition zones where ZNGIs intersect but impact vectors favor exclusion.

Scale of Ecological Level

The hierarchy of biological organization ranging from chemical levels to organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.

Phosphate and Silica

The two primary limiting resources used as examples when discussing coexistence and ZNGIs in phytoplankton competition.

Impact of Species A on Resource

The specific consumption pattern of Species A that reduces the availability of resources $R_1$ and $R_2$ in the environment.