interspecific competition pt 3 (competitive exclusion->competitive release)

competitive exclusion principle

states that “complete competitors” cannot coexist

→ they cannot live in the same niche

complete competitors

two species that live in the same place and have exactly the same ecological requirements

→ meaning that 2 species are competing for absolutely everything in the same space so one species will win over the other

what are the assumptions of the competitive exclusion principle? in other words, what has to be true for the competitive exclusion principle to be achieved?

1) competitors have exactly the same resource requirement

2) environmental conditions remain constant (this is rare..)

what factors affect the outcome of interspecific competition?

1) temperature + pH

2) spatial + temporal variations in resource availability

3) competition for limiting resources

4) resource partitioning

how can competition be influenced by non-resource factors?

environmental factors like temperature, soil/water pH, relative humidity, and salinity could affect plant growth + plant reproduction

→ these are not consumable resources and species do not compete for these

how do environmental conditions change competitive advantage?

environmental variation allows competitors to coexist where under constant conditions, one would exclude the other

climate variations can function as a density-_________ limitation on population density

independent

*the amount of individuals in the population does not CHANGE the weather

→ extreme environmental conditions may depress populations below carrying capacity, allowing sufficient resources for the intervening times

→ this may act to reduce or eliminate competition

competition between species involves multiple resources…what does this mean about a species access to other resources?

competition for one resource can influence an organism’s ability to access another resources

→ for instance, birds fighting over the resource of territory can influence their access to water or food

how do competitive abilities of species change with the environment?

1) change in the carrying capacity related to a changing resource base

2) changes in the physical environment that interact with resource availability

is the superior competitor always superior in varying environmental conditions?

no

salt-marsh zonation

• relative competitive ability of species for nutrients that are influenced by the ability of plants to tolerate increasing physical stress (waterlogging, salinity, oxygen availability in sediments)

• upper distribution boundaries are set by competition for nutrients, and lower boundaries are set by the ability to tolerate physical stress

in competition for nutrients, what are the respective boundaries that plants worry about?

upper boundary: competition for nutrients between other plants

lower boundary: toleration of physical stress

fundamental niche

full range of conditions + resources under which the species can survive and reproduce

realized niche

the portion of the fundamental niche that the species actually exploits

niche overlap

occurs when two or more organisms use a portion of the same resource (food or habitat) simultaneously

the more competition there is, the ____ niche overlap

less

the less competition there is, the _____ niche overlap

more

extensive niche overlap may indicate what?

little competition exists and/or resources are abundant

why can’t species occupy the best part of the fundamental niche?

their access might be restricted due to competition

competitive release

when a species expands its niche in response to the removal of a competitor or when a species invades an island + expands into unoccupied habitats

what are some examples of competitive release?

a decline in one species allows for an increase in another species