E1: Biotic Factors that Limit Distributions
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What are the 4 biotic factors that limit distribution?
• Dispersal • Predators • Disease • Competition
Define competition limiting ditribution.
One species may outcompete another and affect their distribution.
Provide an example of competition.
American Mink introduced to UK, population began to decline. It was found to be due to the Eurasian otters. The otters were better at hunting than the mink, so the mink began to decline.
Define disease limiting distribution.
Being pathogenic toward another organism may also affect their local distribution
Provide an example of disease limiting distribution.
Two waves of disease to native birds in Hawaii spread by mosqiuitos that avaoid cool temps. This led to the birds living only in higher elevations in the mountains.
Define predators limiting distribution.
Being eaten by another organism may limit local distribution.
Provide an example of predation limiting distribution.
Rock Wallabies were limited to rocky regions to escape Red Foxes. Once Red Foxes were poisoned, Wallabies came back around.
Define dispersal limiting distribution.
The organism may not have the ability to go to another area.
What are the three modes of dispersal?
• Diffusion • Jump dispersal • Secular dispersal
Describe diffusion dispersal.
Gradual movement of a population, typically through difficult areas over many generations.
Provide an example of diffusion dispersal.
California sea otter expanding range north and south from 1914 - 1984.
Describe jump dispersal.
Movement of individual organsisms across large distancess
Provide an example of jump dispersal.
Terrestrial species colonizing an island
Define secular dispersal.
Diffusion dispersal where natural selecion causes groups to evolutionary diverge over time.
What is Reid’s Paradox?
Discrepancey between how fast species are able to disperse vs what calculation show they should diperse.
Provide an example of Reid’s Paradox.
Oak trees spreading after glacial recession. observed: 10,000 km calculated: 36 km
Why do we have Reid’s Paradox for colonization?
Colonization rates are driven by extreme dispersers, not the average.