Chapter 14: Competition

Question 1

Who was the first to document carnivory in plants?

Answer 1

Charles Darwin

Question 2

What plants did Darwin study carnivory in?

Answer 2

-Venus Flytrap: inner surface with touch sensitive hairs
-Pitcher Plant: leaves are modified into trap where insects get stuck and tumble into vat of digestive juices

Question 3

Why do some plants eat animals?

Answer 3

-competition among plants can be intense where soil nutrients are scarce
-adaptation to low-nutrient environments

Question 4

Brewer (2003)

Answer 4

removed non-carnivorous competitior plants from around pitcher plants and found that pitcher plant growth rates increased greatly

Question 5

Competition

Answer 5

non-trophic interaction between individuals of two or more species in which all species are negatively affected by their shared use of a resource

Question 6

Interspecific competition

Answer 6

between members of different species

Question 7

Intraspecific Competition

Answer 7

between individuals of a single species

Question 8

Resources

Answer 8

components of the environment that are required by species (food, water, light, space)

Question 9

Fundamental Niche

Answer 9

the full set of resources, plus other biotic and abiotic requirements of a species

Question 10

Realized Niche

Answer 10

the restricted set of resources that a species is limited to, due to species interactions

Question 11

Exploration Competition

Answer 11

-individuals reduce the supply of a resource as they use it
-indirect competition
-Ex: pitcher plants

Question 12

Interference Competition

Answer 12

-one species directly interferes with the ability of its competitors to use a limiting resource
-direct competition
-Carnivores fighting over animal prey

Question 13

Interference Competition in Plants

Answer 13

individuals of one species grow on or shade other species, reducing their access to light

Question 14

Allelopathy

Answer 14

plants of one species release toxins that harm other species

Question 15

When does belowground competition increase?

Answer 15

Nutrient poor soils

Question 16

Wilson and Tilman (1993)

Answer 16

studied grass plants that were transplanted into fertilized and unfertilized plots

Question 17

In Wilson and Tilman (1993), when was below ground competition most intense?

Answer 17

nitrogen limited plots

Question 18

In Wilson and Tilman (1993), when was above ground competition for light increased?

Answer 18

when light levels are low

Question 19

Tilman et al. (1981)

Answer 19

2 diatom species showed that when the species were grown together, they competed for silica, and one species drove the other to extinction

Question 20

Effects of competition are _____ or _____

Answer 20

unequal or asymmetrical (one species is harmed more than the other)

Question 21

What are the ends of the continuum called that demonstrate how strongly each competitor affects the other?

Answer 21

amensalism: –/0 interactions; individuals of one species are harmed while individuals of the other species are not affected at all

Question 22

Brown and Davidson (1977)

Answer 22

-exclusion experiments with rodents and ants that eat the same seeds
-when either rodents or ants were removed, the group that remained ate as many seeds as rodents and ants combined

Question 23

Schoener (1993)

Answer 23

of 390 species studied, 76% showed effects of competition under some conditions, 57% showed effects under all conditions tested

Question 24

Connell (1983)

Answer 24

competition was important for 50% of 215 species in 72 studies

Question 25

Gurevitch et al. (1992)

Answer 25

analyzed the magnitude of competition in 93 species in 46 studies: competition had significant effects on a wide range of organisms

Question 26

Biases to competition biases:

Answer 26

-researchers may not publish studies that show no significant effects
-a tendency for investigators to study species they suspect will show competition

Question 27

Competion is _____, though not ____

Answer 27

common, ubiquitous

Question 28

2 possible outcomes of Interspecific Competition

Answer 28

-Competitive exclusion
-competitive coexistence

Question 29

Competitive Exclusion

Answer 29

dominant species prevents another species from using essential resources; the inferior species may become locally extinct

Question 30

Competitive Coexistence

Answer 30

ability to coexist despite sharing limiting resources

Question 31

Gause (1930s)

Answer 31

-populations reached a stable carrying capacity when grown alone
-2 were able to coexist by feeding on different food items, growth rates were slower
-1 drove another to extinction, both feed on floating yeast cells

Question 32

Competitive Exclusion Principle

Answer 32

two species that use a limiting resource in the same way cannot coexist indefinitely

Question 33

Resource Partitioning

Answer 33

species using a limited resource in different ways can coexist

Question 34

Stomp et al. (2004)

Answer 34

-cyanobacteria in Baltic Sea
-One species absorbs red more efficiently, the other absorbs green
-each species could survive when grown alone on either wavelength
-When grown together, one drove the other to extinction, depending on light wavelength
-They coexist due to resource partitioning

Question 35

Character Displacement

Answer 35

when two species compete for resources, natural selection may favor phenotypes that allow them to partition resources, decreasing competition intensity

Question 36

Look at slides 41-52

Question 37

The outcome competition between species can be changed by…

Answer 37

features of the physical environment, disturbance, and interactions with other species

Question 38

Physical Environment

Answer 38

soil type influences competition between bedstraw species

Question 39

Interactions with other species

Answer 39

presence of herbivores can reverse the outcome of competition between encrusting marine algae species, and between ragwort and other plant species

Question 40

Connell (1961)

Answer 40

-examined factors that influence distribution, survival, and reproduction of two barnacle species

Question 41

Natural Experiment

Answer 41

a situation in nature that is similar in effect to a controlled removal experiment

Question 42

Patterson (1980,1981)

Answer 42

-studied chipmunk species in mountain forests and found
-When a species lived alone on a mountain, it occupied a wider range of habitats than when it lived with a competitor species

Question 43

What may modify competitive interactions and ultimately influence abundance and distribution of species?

Answer 43

climate change

Question 44

What did warming experiments on beach grass species show?

Answer 44

that elevated temperatures can increase the likelihood of species coexistence and change the distributions of the two species

Question 45

Fugitive Species

Answer 45

they must disperse from one place to another as conditions change