Ecology Lecture Exam 4 notes

Competition

Two populations affecting each other adversely because they both need a limited resource

Resource

Any factor used by organism that promotes survival and reproduction

Give examples of resource

Space, food, water, mates

How can you tell competition is a negative interaction?

Use/set up a Common Garden Experiment

What are the two types of Competition?

1. Direct

2. Indirect

Direct competition

Contest, fight ->Eventually one species or individual controls the resource

Examples of Direct competition

Hyenas vs lions

Indirect competition

Scramble, exploitative ->Everyone is using same resource -> Everyone loses, resource used up

Examples of Indirect competition

Cheetahs/leopards and water holes

What are the 2 levels that competition manifests?

1. Intraspecific Competition

2. Interspecific Competition

Intraspecific Competition

Competition between members of same species

Interspecific Competition

Competition between members of different species (due to same limited resources)

Who developed Interspecific Competition (I and j)

Developed by Lolka-Voltaire model of competition

aij

coefficient of competition (Measures the impact (decline in population growth) on one species (i) by another species (j))

Nj

number of individuals in competing species j

What are the 3 outcomes of aij or aji?

1. Can be 0

2. Can be 1

3. Can be less than 1 (<1) or greater than 1 (>1)

What does it mean if the outcome of aij or aji is 0?

Means no competition

What does it mean if the outcome of aij or aji is 1?

Means that each species has an identical impact on the other

What does it mean if the outcome of aij or aji is greater than or less than 1?

Means that 1 species has a greater impact on the growth of the other species (This is the usual case (Asymmetrical outcome))

Ex. what does it mean if aij= 3?

this means that each individual of j has the same impact on population growth of i as 3 individuals of i (basically each individual j is worth the same as 3 individual i's)

4 possible outcomes of competition

1. Species 1 always wins

2. Species 2 always wins

3. Either species 1 or species 2 wins (depends on environment)

4. Apparent Coexistence

Competitive Exclusion Principle

two species with identical resources

Can requirements coexist indefinitely? Why or why not?

No, requirements cannot coexist indefinitely, because ultimately one competitor will be more effective (winner) and one will go extinct (loser)

When does Co-existence occur?

When intra specific competition is stronger than inter specific competition (Neither grows at its biotic potential and coefficient of competition is weak)

3 out 4 outcomes

Means Single winner

1 outcome

Means Co-existence

Is co-existence rare?

No

What are the 4 Competitive Assumptions?

1. Environment is stable/ unchanging (not true)

2. Competition is only important biological interaction (its not)

3. No migration between populations (but there is)

4. Resource competition is complete/complete overlap in resource use

Resource use is often incomplete/aren't identical. True or false

True

What can generally be done to reduce overlap (competition)?

Shifting resource use

What reducing overlap by shifting resource use generally look like?

Narrowing or displacement of resources used

Resource Partitioning

Competing species use different portions of the same resource

Give an example of Resource Partitioning

Chipmunk species 1 and 2 in Oregon Mountains (SW USA) (species 1 on top, and species 2 is under the line)

How does competition drive evolutionary change?

Interspecific competition reduces fitness

What does interspecific competition reducing fitness mean?

Means that individuals with alleles/genotypes that reduce time spent competing, should have higher fitness (faster, stronger, smarter etc) than individuals that compete more) (their alleles will increase in proportion in the population)

Character Displacement

Competition is a selective agent to cause competition species to become more different

What is the result of character displacement?

Results in less competition

Consumer/consumed Interactions

One species (individual; consumer) exploits another species (individual; consumer) as a food resource (this is a positive/negative interaction, or +,-)

Types of consumers

1.Predators

2.Parasites

3.Parasitoids

4.Brazers/herbivores

What do Predators do to resources, and what is being consumed?

Kills resource (short association) Consumed=prey

What do Parasites do to resources, and what is being consumed?

Do not kill resource (long association) Consumed=Host

What do Parasitoids do to resources, and what is being consumed?

Parasitoids Do not kill resource (long association) Consumed=Host

What do Brazers/herbivores do to resources, and what is being consumed?

Do not kill resource (short association) Consumed=?

What is the problem with being too effective?

In competition if one species is very effective then the competition goes extinct/ this is good/ It frees up resources. In consumer/consumed interactions, the consumed goes extinct, consume runs out of food, goes extinct themselves. (important in parasitoid/host relationships (Food + habitat))

The Prey models are linked because?

Because population size of both is in each Model

Increased size of host population leads to

leads to increasing death due to predation

Increased size of host population lead to

more predation

Increased size of predator population leads to

increasing predation

Ultimately growth of predator population leads to

decrease in prey population and leads to oscillations cycling population size for both population

Refugia

Place of safety

Oscillations are possible, but with other "conditions", what are these conditions?

1. Spatial Refugia

2. Numerical Refugia

Spatial Refugia

Places where the exploited (prey) have protection from predators/exploiders (ex. burrows, dispersal, microclimates, etc)

Numerical Refugia

Safety in numbers (numbers alone reduce probability of consumption)

What are the 3 ways predator species respond?

1. Type 1 Response

2. Type 2 Response

3. Type 3 Response

Type 1 Response

Constant rate of consumption/ kill prey density rises, up until a max number

Type 2 Response

The number of prey consumed rises, but at a decelerating rate (why? Handling time)

Type 3 Response

Consumption starts slow, then rate increases up to a point and then consumption rates decreases again (Why? Handling Time and learning)

Other factors that promote co-existence

1. Immigration

2. Predator inefficiency or enhanced prey escape

3. Alternative prey ideas

4. Other density dependent factors that

(Fill in) Unique consideration/ parasites are both ______ and ______, especially parasitoids

Habitat, Food

Why are parasites both habitat and food?

Because they kill their host

So natural selection favors genotypes that make parasitoids a little less virulent (lethal). True or false

True, natural selection favors genotypes

How do parasites gain access to host by?

1. Burrow/penetrate (ex. ducks-- swimmers itch)

2. Oviposited (ex. butterflies)

3. Oral/ Anal cavity (ex. roundworms)

4. Vector transmitted (ex. malaria)

Types of Parasites

1. Endoparasites

2. Ectoparasites

3. Pathogens

4. Hyperparasites

Endoparasites

Live inside hosts (Positive: Environment protected close to food) (Negative: Contend with host immune system (no easy escape))

Ectoparasites

Live outside hosts (Positive: Easy escape, No immune system) (Negative: Contend with outside environment)

Pathogens

Parasites that cause disease

Hyperparasites

Parasites of parasites

Many varied ecological/ evolutionary implications of species interactions with parasites

1. Can change behavior of host (ex. fungus/ flies ->changed fly behavior)

2. Mimicry

3. Mutualism

Mimicry

Species evolve patterns that resemble unrelated species

Batesian

one is toxic, one is palatable

Mullerian

neither species is palatable ->When toxic species converge on same patterns

Mutualism

Both species benefit in growth, survival, etc.

What are the 2 ways that Mutualism can manifest?

1. Obligate

2. Facultative

Obligate

Cannot live without each other; Tight association between 2 species (ex. fig trees, fig wasps)

Facultative

Can live without each other; Loose/diffuse associated multiple species involved on one side of interaction (ex. bees/ flowers, deer/different plant seeds)

Co-evolution (reciprocal evolution)

Change in one affects the other and so on

Ecological sorting

idea that out of a subset of species-these aligned with traits benefiting each other (opportunity associations)

Emerged from parasite/host interactions

Evolution decrease virulence/increased tolerance of host; Evolved to being benign; Evolved to being beneficial