1. 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

2. 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)

3. Cattle egret (Bubulcus ibis)
Arrived by flying from Africa in late 1800s

4. European starling (Sturnus vulgaris)
Intro to Central Park in 1896
Wanted birds of Shakespeare

5. Oaks across Britain and Ireland

6. 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

7. Recolonization of Krakatau

11. Secular Dispersal
Evolutionary divergence through range expansion
Evolutionary time scale

13. Mechanisms of Dispersal
Active
Capacity to travel long distances (flight, walking, or swimming)
Best example are migratory animals

14. Migratory route of golden plover (Pluvialis dominica)

16. 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

19. Water Dispersal

20. Phoresy

21. Barriers
Long-distance dispersal
Encounter obstacles
Unfavorable environmental conditions
Tolerate, overcome, or dead end?

22. 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

23. Sheephead minnow (Cyprinodon variegatus)

24. Contrast with Centrarchids

25. Differences in mountain barriers – temperate vs.
tropics

26. Mammals, reptiles, etc. – aided by past vegatation

27. Temporal barriers – temperate/polar water bodies.
Movement over ice

28. Ecological Barriers
Competition
Predation
Habitats – refusal to cross

29. Corridors
Allow dispersal by permitting movement
Contemporary examples
Historical – account for related of different species or even same species in widely separated regions

31. Tethyan Seaway

33. Filters
Restrictive dispersal pathway
Conditions restrictive to some species, not others
Can be biotic or abiotic

34. Two-way Filter