Chapter 14: Competition Flashcards
Who was the first to document carnivory in plants?
Charles Darwin
What plants did Darwin study carnivory in?
-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
Why do some plants eat animals?
-competition among plants can be intense where soil nutrients are scarce
-adaptation to low-nutrient environments
Brewer (2003)
removed non-carnivorous competitior plants from around pitcher plants and found that pitcher plant growth rates increased greatly
Competition
non-trophic interaction between individuals of two or more species in which all species are negatively affected by their shared use of a resource
Interspecific competition
between members of different species
Intraspecific Competition
between individuals of a single species
Resources
components of the environment that are required by species (food, water, light, space)
Fundamental Niche
the full set of resources, plus other biotic and abiotic requirements of a species
Realized Niche
the restricted set of resources that a species is limited to, due to species interactions
Exploration Competition
-individuals reduce the supply of a resource as they use it
-indirect competition
-Ex: pitcher plants
Interference Competition
-one species directly interferes with the ability of its competitors to use a limiting resource
-direct competition
-Carnivores fighting over animal prey
Interference Competition in Plants
individuals of one species grow on or shade other species, reducing their access to light
Allelopathy
plants of one species release toxins that harm other species
When does belowground competition increase?
Nutrient poor soils
Wilson and Tilman (1993)
studied grass plants that were transplanted into fertilized and unfertilized plots
In Wilson and Tilman (1993), when was below ground competition most intense?
nitrogen limited plots
In Wilson and Tilman (1993), when was above ground competition for light increased?
when light levels are low
Tilman et al. (1981)
2 diatom species showed that when the species were grown together, they competed for silica, and one species drove the other to extinction
Effects of competition are _____ or _____
unequal or asymmetrical (one species is harmed more than the other)
What are the ends of the continuum called that demonstrate how strongly each competitor affects the other?
amensalism: –/0 interactions; individuals of one species are harmed while individuals of the other species are not affected at all
Brown and Davidson (1977)
-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
Schoener (1993)
of 390 species studied, 76% showed effects of competition under some conditions, 57% showed effects under all conditions tested
Connell (1983)
competition was important for 50% of 215 species in 72 studies
Gurevitch et al. (1992)
analyzed the magnitude of competition in 93 species in 46 studies: competition had significant effects on a wide range of organisms
Biases to competition biases:
-researchers may not publish studies that show no significant effects
-a tendency for investigators to study species they suspect will show competition
Competion is _____, though not ____
common, ubiquitous
2 possible outcomes of Interspecific Competition
-Competitive exclusion
-competitive coexistence
Competitive Exclusion
dominant species prevents another species from using essential resources; the inferior species may become locally extinct
Competitive Coexistence
ability to coexist despite sharing limiting resources
Gause (1930s)
-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
Competitive Exclusion Principle
two species that use a limiting resource in the same way cannot coexist indefinitely
Resource Partitioning
species using a limited resource in different ways can coexist
Stomp et al. (2004)
-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
Character Displacement
when two species compete for resources, natural selection may favor phenotypes that allow them to partition resources, decreasing competition intensity
Look at slides 41-52
The outcome competition between species can be changed by…
features of the physical environment, disturbance, and interactions with other species
Physical Environment
soil type influences competition between bedstraw species
Interactions with other species
presence of herbivores can reverse the outcome of competition between encrusting marine algae species, and between ragwort and other plant species
Connell (1961)
-examined factors that influence distribution, survival, and reproduction of two barnacle species
Natural Experiment
a situation in nature that is similar in effect to a controlled removal experiment
Patterson (1980,1981)
-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
What may modify competitive interactions and ultimately influence abundance and distribution of species?
climate change
What did warming experiments on beach grass species show?
that elevated temperatures can increase the likelihood of species coexistence and change the distributions of the two species
Fugitive Species
they must disperse from one place to another as conditions change
