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Distributions - Coggle Diagram
Distributions
Fragmentation can produce metapopulations
Species may survive as metapopulations, even though individual
populations are prone to extinction
Levins model
assumes
equal patch size
Populations are at carrying capacity (occupied or not occupied)
Extinction risk is a set rate
not equal across all populations
Distance of patches
Extinction debt
Changes in environments might be expected to cause extinctions but sometimes these extinctions are delayed
Consequence of isolated populations
(Berger (1990) Conservation Biology 4: 91-98)
Bighorn sheep Ovis canadensis
Can result in small populations sizes that have no support from other populations
100% of populations <50 sheep went extinct
within 50 years
Rapid loss of populations was not likely to be caused by food shortages, severe weather, predation, or interspecific competition
Small populations are prone to extinction
(Schoener & Spiller 1987 Nature 330: 474 - 477)
Orb spiders on islands in the Bahamas
