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Diffusion Dispersal Slow expansion from previous range into new areas Gradual process as species acclimate to conditions and taxa at margins of range Can follow jump dispersal (next example)
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Dispersal Movement of species leading to range expansion Hotly
debated Dispersalists vs. Extensionists Continental drift changed
debate Long-distance distance dispersal vs. vicariance Read Box 6.1
Diffusion Dispersal Slow expansion from previous range into new
areas Gradual process as species acclimate to conditions and taxa
at margins of range Can follow jump dispersal (next example) Cattle
egret (Bubulcus ibis)
Arrived by flying from Africa in late 1800s European starling
(Sturnus vulgaris)
Intro to Central Park in 1896 Wanted birds of Shakespeare Oaks
across Britain and Ireland Jump Dispersal Species skips over area
outside its range to new location Island colonization Some species
lacking from islands limited ability to disperse (mammals,
amphibians, freshwater fishes) Also occurs across continents
Recolonization of Krakatau Secular Dispersal Evolutionary
divergence through range expansion Evolutionary time scale
Mechanisms of Dispersal
Active Capacity to travel long distances (flight,walking, or
swimming) Best example are migratory animals Migratory route of
golden plover (Pluvialis dominica) Mechanisms of Dispersal
Passive Wind, water, or on animals Plants best examples Also
animals (insects), fungi, and bacteria Phoresy animal hitching a
ride on another animal for dispersal Water Dispersal Phoresy
Barriers Long-distance dispersal Encounter obstacles Unfavorable
environmental conditions Tolerate, overcome, or dead end?
Physiological Barriers
Conditions fall outside range of tolerance Not able to cross
barriers History of area may have allowed passage and distributions
seen today Freshwater lake fishes only found in multiple locations
if lakes were connected at one time Some lakes are fishless not
because of tolerance Marine fish vs. freshwater fish Sheephead
minnow (Cyprinodon variegatus) Contrast with Centrarchids
Differences in mountain barriers temperate vs.
tropics Mammals, reptiles, etc. aided by past vegatation Temporal
barriers temperate/polar water bodies.
Movement over ice Ecological Barriers Competition Predation
Habitats refusal to cross Corridors Allow dispersal by permitting
movement Contemporary examples Historical account for related of
different species or even same species in widely separated regions
Tethyan Seaway Filters Restrictive dispersal pathway Conditions
restrictive to some species, not others Can be biotic or abiotic
Two-way Filter