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Dispersal

Dispersal. Diffusion. Gradual movement Over several generations. California Sea Otter. Thought to be extinct in 1911 Found at Point Sur in 1914 More rapid southern expansion. Jump Dispersal. Example: oceanic islands Mostly by volant organisms (flight) ex.: Galapagos Islands

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Dispersal

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  1. Dispersal

  2. Diffusion • Gradual movement • Over several generations

  3. California Sea Otter • Thought to be extinct in 1911 • Found at Point Sur in 1914 • More rapid southern expansion

  4. Jump Dispersal • Example: oceanic islands • Mostly by volant organisms (flight) ex.: Galapagos Islands • Rare, large (distance), and "surprising" events • Explains large discontinuous distributions of some organisms • Explains taxonomic similarity of distant biotas and populations

  5. Collared Dove Expansion

  6. Dispersal Polymorphism • Gymnarrhena micrantha

  7. Philopatry • Tendency to disperse near close kin Belding’s Ground Squirrel

  8. Barriers • Physical • human introductions indicate how effective barriers can be • overcome resistant propagules • "weeds" are good dispersers (hardy) • Physiological • land-water • salinity for aquatic organisms • temperature: both low and high • Ecological-Behavioral • predators • strong fliers that won't cross water

  9. U.S. Starling Dispersal 100+ birds added to Central Park in late 1800’s

  10. Gypsy moth • Accidental introduction at end of 19th century

  11. River barriers

  12. Acorn dispersal by Jays The more seeds carried, the farther the distance

  13. Neritina dispersal

  14. Dispersal Distance Eucalyptus Isolated tree Edge of forest Longocarpus

  15. Measuring Dispersal Distance • Breadth of normal distribution characterized by standard deviation (s) • Variance : • If mean (release point) is 0, & distance from release site(xi-mean) is di, then: • Distance over time is:

  16. Dispersal vs. range

  17. Birth nest to yearling nesting House wren nesting at distances (1000 ft segments) from nest where hatched

  18. Dispersal for mating Distance from birth site to mating site for the Great Tit

  19. Inbreeding vs. Outbreeding • In many bird populations, about 50% of the birds in an area are immigrants. • Great Tit study - 22 % of pairings were from resident males & females • Inbred nestling mortality = 27.7 % • Outbred nestling mortality = 16.2%

  20. Opossum expansion Climate related?

  21. Maple/Hemlock expansion

  22. Large seeds and fruits Long-lived plants Low relative growth rates Strong competitive ability Predator defenses in plants Innate, transient dormancy High decay rates of soil seed populations Flat dispersal curve Stable populations of plants Small seeds Short-lived plants High relative growth rates Weak competitive ability Predator defenses in seeds Enforced dormancy dependent upon burial Low decay rates of soil seed populations Steep dispersal curve Unstable populations of plants Dispersal in Space Dispersal in Time

  23. Seed Dormancy • Innate dormancy - from when seed first produced • Induced dormancy - internal, but first induced by environmental factor • Enforced dormancy - environmental factors

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