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Dispersal

Dispersal . Landscape Ecology. Definitions. Dispersal Spreading of individuals away from others Migration Mass directional movements of large numbers of species from one location to another. Question/Comments. Do all species disperse?. Yes… Some by choice, some by chance

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Dispersal

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  1. Dispersal Landscape Ecology

  2. Definitions • Dispersal • Spreading of individuals away from others • Migration • Mass directional movements of large numbers of species from one location to another.

  3. Question/Comments

  4. Do all species disperse? • Yes… • Some by choice, some by chance • Chance can be influenced by evolution. • E.g. dandelions sees are puffy for a “reason”.

  5. Dispersal • Why disperse? • Escape immediate environment. • Relieve local congestion. • Discovery Dispersal • 1) Exploring, picking, then settling • 2) Exploring, staying. • Non-discovery dispersal • Matter of change, e.g. seeds.

  6. Do animal moves randomly? • Random • Correlated random walk • Memory – making a decision. • Does it depend on patch type?

  7. Do animal moves randomly? • Usually no…. • But that is as individuals, do they as a group?

  8. Examples – Fire Ants

  9. European Starling

  10. How to model this spread? • What do we need to know about a population? • How far they move? • How fast the population grows? • Suitable Habitat?

  11. Integrodifference Equation

  12. Types of model? • Scientific or Statistical? • Analytical or Simulation? • Static or dynamic?

  13. Modified diffusion equation

  14. How to model this spread? • Diffusion equation?

  15. 2004 Distribution

  16. Lake Mead & Havasu Reservoirs in OK and KS in Verdigis River basin Inland Lake Distance to Great Lakes 2400

  17. Inland Lake Distance to 1993 Distribution 1700

  18. Scaling Factor Area Distance & coefficient Number of Boats Gravity Models – primary spread from the Great Lakes

  19. Types of model? • Scientific or Statistical? • Analytical or Simulation? • Static or dynamic?

  20. United States Gravity Model • Basic Information - • Based on 210 Watersheds • Estimate # of boaters/watershed • Sum lake area/watershed • How to parameterize? • Boat surveys • Local information • Primary Question – • How many boaters from areas with zebra mussels are traveling to western waters?

  21. United States Gravity Model From Bossenbroek et al. 2007 Conservation Biology

  22. From Bossenbroek et al. 2007 Conservation Biology

  23. 2007 Distribution

  24. Predict the spread of emerald ash borer • Local Dispersal • Human-mediated Dispersal

  25. Yr 2 Yr 3 Modeling Dispersal • Natural Spread Linear Distance Yr 1 Time

  26. Yr 3 Yr 2 Modeling Dispersal • Long-distance spread Linear Distance Yr 1 Time

  27. Predict the spread of emerald ash borer • Does natural dispersal account for the rapidity with which the emerald ash borer has spread, even at the county scale?

  28. Diffusion Modeling • Used a derivation of Skellam’s diffusion equation Toledo 2005 Can diffusion explain this rate of movement? 2004 Croskey 2009 - Thesis

  29. Estimating Diffusion Model Parameters • VF= velocity of the invasion front • Observed in Lucas County Ohio • 16 – 40 km/year • D = diffusion coefficient • Reported movement capabilities of EAB • 0.8 – 20 km/year • r = intrinsic rate of increase • r values for other beetles • 0.1 – 9.1 • Force the model to fit observations by solving for r and D Croskey 2009 - Thesis

  30. Diffusion Model Alone Cannot Explain EAB Spread • When D is estimated (obs = 0.8 – 20 km/year) • mean = 802.80 km/year • When r is estimated (obs = 0.1 – 9.0 ): • mean = 76.04 Natural dispersal is not responsible for the rate at which the emerald ash borer has spread Croskey 2009 - Thesis

  31. Predict the spread of emerald ash borer • Develop models for both: • Local Dispersal • Human-mediated Dispersal

  32. Natural (or local) Dispersal of EAB in Ohio Prasad et al. 2010

  33. Predict the spread of emerald ash borer • Local Dispersal • Flight (~2 km/yr) • Local human spread (~20 km/yr) • Human-mediated dispersal • Campers moving firewood • Hitchhikers on cars, trucks, etc. • i.e. road networks. • Wood products industry

  34. Predict the spread of emerald ash borer:Human-mediated dispersal Campers with Firewood Bossenbroek & Jerde – in review

  35. Natural and Human-Mediated Dispersal of EAB in Ohio Prasad et al. 2010

  36. Compared model to known distribution • Examined the model predictions to the patterns of the human factors included. • We examined 11 of the major routes from Detroit, MI, to major cities in Ohio • And included one turn only onto an adjoining highway. • Then buffered these highways at 1, 2, and 4 km. • Results: • 52% of the known locations of EAB fell within 1 km • 64% fell within 2 km • 81% fell within 4 km • these few roads that represent only 34.7% of the total road length used in the modeling. Prasad et al. 2010.

  37. This result highlights the importance of the role of major highways that are in a connected road network in spreading the emerald ash borer.

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