inter and intraspecific competition

intraspecific

competition within species

interspecific competition

competition between two different species

niche

the constellation of environmental conditions under which a species can survive

• “multi-dimensional box” that defines the limits to survival for each environmental factor (each dimension)

  • factors include temperature, rainfall, nutrient levels, etc.

fundamental niche

conditions in which a species could potentially live

realized niche

the actual space and resources a species occupies and utlizes within its environment

competitive exclusion

complete competitors cannot co-exist

• has assumptions

competitive exclusion assumptions

• competitors have exactly the same resource requirements

• environmental conditions stay constant

paradox of plankton

asks how a large number of competing phytoplankton species can coexist in marine ecosystems when, according to the competitive exclusion principle, they should not be able to coexist due to limited resources

types of competitive interactions

resource & interference competition

resource competition

one individual deprives another of a resource through the consumption of that resource (indirect)

self-thinning

a form of resource competition; intraspecific resource competition causes the population density to decline over time

• density decreases, size of survivors increases

• happens in plants and animals

interference competition

direct interactions result in restricted access to a resource

• allelopathy (chemical warfare)

• territoriality (what you see on discovery channel)

• preemption (I was here first, so you can’t be)

forms of intraspecific population control

• density-dependent growth and development

• density-dependent mortality and self-thinning

• density-dependent effect on reproduction

  • competition between finding a mate

a12

per capita effect of species 2 on species 1 (defines the strength of the relationship)

a21

per capita effect of species 1 on species 2 (defines the strength of the relationship)

character displacement

when two species compete, natural selection may reduce the strength of competition by changing some characteristics of one or both species

• results in resource partitioning

1 increase, 2 decrease

green: above K, decrease

orange: below K, increase

what does the blue line represent?

the net result/ movement

1 increase, 2 decrease

green: below K, increase

orange: above K, decrease

increase in both populations

green: below K, increase

orange: below K, increase

decrease in both populations

green: above K, decrease

orange: above K, decrease