Species interactions 1

Horizontal diversity

Taxonomic or functional diversity within a single trophic level

Trophic level

feeding position of species in an ecosystem

Vertical diversity

taxonomic or functional diversity in feeding or trophic interactions in an ecosystem

1. interference competition

2. exploitative competition

Two main classes of competition

1. classical experiments

2. mathematical models

Have developed a theoretical foundation for studying competition in nature [2]

Intraspecific competition

competition with members of your OWN species

Interspecific competition

competition between individuals of different species

Interference competition

Competition is a direct interaction between individuals

Wolf packs in Greater yellowstone ecosystem

Example of intraspecific interference competition

Wolves and coyotes in the greater yellowstone ecosystem

example of interspecific interference competition

Interference competition

Competition is a direct interaction between individuals. Each has a negative impact on the other

Exploitative competition

Competition is an indirect interaction between individuals

Squash in the garden. cucumbers and onions interfering for light, nutrients, water

Example of interspecific exploitative competition:

Taking up resources before others are able to

How do individuals harm each other in exploitative competition?

R* theory

Theory for determining the winner of competition for resources

Ri*

Concentration of a limiting resource a twhich species will have a reproductive rate exactly equal to its mortality rate

It requires the lowest level of resources to persist (ie it can persist in the poorest conditions)

why is the species with the lowest R* the winner of competition?

Increased introspecific competition

Population growth slows as population size increases due to

Interspecific competition

Mechanism that causes the realized niche to be smaller than the fundamental niche

stoichiometric bottleneck at the plant-herbivore interface

Plants are generally a low quality (high carbon) resource which creates a:

Most of what they eat is not digested

excreted, egested, or respired

How do herbivores get C:N of 6.1 if they eat resources that have a ratio of 25:1? [2]

2.5-3.5% per day (12.5-17.5kg)

How much can moose eat per day in summer

Decreases plant biomass

Grazing effect on plant biomass

Increase primary production

Grazing effect on primary production

Grazing Optimization

Herbivores improve an ecosystems nutrient conservation efficiency enough to compensate for loss of plant biomass to grazing

Low quality

Having a High C:N ratio food:

non chemical leaf and stem characteristics

Physical defensive traits of plants:

Gross morphology

includes physical structure and size of plants

Life-history

Rate of growth, phenology, and investment in reproductive structures

Toxins or digestion-reducing substances that can kill, impair, or repel herbivores

Chemical defense of plants:

Cyanogenic glycosides in seeds (apples)

Example of plant toxins

Life-history traits and gross morphology

Best predictors of herbivore susceptibility:

1. food availability

2. consumptive effects of predators

3. non-consumptive effects of predators

Prey populations are influenced by: [3]

Use of refugia and diversity of defense of strategies

Prey populations can persist in the presence of predators through the use of:

Trophic cascade

Strong predation pressure can lead to:

1. can double in size each generation

2. may lead to over-browse food resources

impact of food supply of lynx hair cycle

1. multiple predators feed on hair

2. lynx can show numerical response

predator role of lynx hair cycle

elevated stress (increase in glucocorticoids)

Increased predation risk leads to what in organisms?

habitat shifts (predator avoidance)

foraging shifts (high carb diet to fuel greater metabolism

elevated stress can lead to these shifts:

small litters

lighter offspring

stressed mothers effect on offspring

reduced # song sparrow per year by 40%

predation risk on sparrow offspring

Batesian Mimicry

Harmless (nontoxic) species exhibit similar color to noxious species in the same area

Mullerian Mimicry

toxic/noxious species that share similar colouration

Space

spatial separation may reduce encounter rates with predators

Numbers

Mass reproductive events that may saturate predators

Size

Larger prey are harder to kill

1. batesian mimicry

2. mullerian mimicry

3. space

4. numbers

5. size

Prey strategies:[5]

Monarch butterflies and another butterfly

batesian mimicry example:

Common wasp, germain wasp, and paper wasp similar colouring

example of mullerian mimicry