Competitive Exclusion and Species Coexistence

Learning goal:
* Understand the ultimate outcome of assymetric competition = competitive exclusion, and what the consequences are
* Be able to describe the possible reasons the species coexist despite their competing for the same limiting resource

The Competitive Exclusion Principle
niche = the resources an organism consumes, how it obtains it + where it lives
If niches are very similar between two competing species,  i.e. they use the same resources at the same place and the same time, the superior competitor will drive the inferior competitor to local extinction


Competition and species co-existence: resource partitioning
Species may co-occur in communities, despite having similar resource needs (limiting resources), by obtaining the resources in different ways: resource partitioning
In plants, resources used are similar, and partitioning by form isn't usually an option. Partitioning usually involves obtaining resources at different places or different times
For animals, partitioning may involve spatial and temporal differences, as well as using slightly different limiting resources (e.g. different prey species)

Additional factors that contribute to species coexistence:

* Competition for more than one resource (e.g. seasonal or spatial variation in limiting resources)
* Competition for limiting nutrients combined with gradients of physical factors (temp, salinity, pH); competitive superiority may vary as physical environmental conditions change
* Resource fluctuations and non-equilibrium conditions- disturbance, predation; e.g. superior competitors may be preferred prey
* Evolution of character traits that enhance resource partitioning; morphological specialization may allow species to narrow their niches