xxxx
Steven Dutch, Natural and Applied Sciences, University
of Wisconsin - Green Bay
First-time Visitors: Please visit Site Map and Disclaimer. Use
"Back" to return here.
Mechanisms of Coexistence
This question has long been asked by ecologists, and is important
now if we wish to discover how humans and other species can coexist.
Four primary mechanisms underlying coexistence exist:
Niche relations. Species coexist because
they have different environmental requirements (soil, water, climate, etc.), so
that no species will competitively exclude another. These mechanisms
operate only over distances in which individuals directly interact with
another (spread of roots in a plant, the size of a home range in an animal).
Habitat heterogeneity.
Species coexist because of different environmental conditions found within a
region, so that a species will have at least one place where it can not
be competitively excluded. The more combinations of environmental
conditions, the greater the number of species which can coexist. This
factor operates over distances in which environmental change is most pronounced
(10-meter to 1000 kilometer)
Mass effect. Species coexist because
they are constantly dispersing in from other habitats they disperse to. If
a bog and dry prairie are neighbors, there will be a few dry prairie plants in the bog. These strays will soon be
eliminated from the habitat, but by the time that happens, more individuals have
colonized. this effect will be most pronounced in regions where many
different habitats are in close proximity, and will be most pronounced at 1/2-5
kilometer distances.
Trophic equivalency. Species coexist
because habitats are isolated from each other, limiting the number of potential
competitors, and the rate of competitive exclusion. If isolation between
habitats is frequent, many species with similar niches may thus be able to
coexist. This effect is most often thought to be important between
continents. However, it may also be important at much smaller distances
(100 kilometers or less.)
These explanations can be put into two major classes:
Environment and niche relations: coexistence is possible because
of differences between requirements of species and differences in the
environment (Niche relations and Habitat heterogeneity)
Spatial and temporal constraint: coexistence is possible because
species have not been able to locate all potential habitats due to dispersal
limitation and/or historical factors (Mass effect and Trophic equivalency)
Of these, the first class of explanations have been most thoroughly
investigated by ecologists. Only within the last few decades have the
latter explanations been formally considered.
xxx
Return to Professor Dutch's Home Page
Created 2 September 2011, Last Update
02 September 2011
Not an official UW Green Bay site