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Dispersal Models

Dispersal Models. General Module B2 Spatial Modelling in Ecology, 5 ECTS Aims Develop programming skills Implement , apply and critically assess computer models Understand the role of spatial processes for ecosystem dynamics Confronting models with data Content

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Dispersal Models

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  1. Dispersal Models • General • Module B2 SpatialModelling in Ecology, 5 ECTS • Aims • Developprogrammingskills • Implement, applyandcriticallyassesscomputermodels • Understand theroleofspatialprocessesforecosystemdynamics • Confrontingmodelswithdata • Content • Implement, applyandcriticallyassesscomputermodels • Importanceofdispersalformigrationandpopulationpersistence • Approaches tomodellingdispersal: • Individual-based (e.g. random walk) • Dispersalkernels (e.g. diffusion) • Network approaches • Long-distancedispersal • Fitting dispersalmodelstodata • Methods • Computer exercises - Programming (R language) - (groupwork) • Literaturestudy • Exam • Essay/report (8-12 pages incl. figures) • Time and Place • Mo: 10:00-13:00 (S 123); We.:14:00-19:00; Fr.: 09:00-12:00, S22 (GEO) (Jan 7 – Feb 8 2009)

  2. Overview • What is dispersal? • How does dispersal affect the spatial distribution of populations? • Metapopulation models

  3. Some terminology • Dispersal: The movement away from an existing population or away from the parent organism • Colonization: The foundation of a new population as a consequence of the dispersal of offspring to an unoccupied site, and the subsequent establishment of a population in this site. • Migration: The spread of a species into a region that previously was not part of its range Wikipedia, Biological dispersal Schurr, Frank (2005), PhD thesis, p. 2

  4. Why dispersal matters • The dynamics of populations depends on the four demographic processes of birth, death, immigration and emigration. • This 'fact of life' defines - in the words of Begon, Harper and Townsend (1996) - 'the main aim of ecology: to describe, explain and understand the distribution and abundance of organisms'. • Dispersal determines two of the four demographic processes, namelyimmigrationandemigration. Schurr, Frank (2005), PhD thesis, p. 1

  5. Benefits of dispersal • Offspring survival is often (but not always) higher away from the parent (density-dependent predation or pathogens; competition with adults) • Reach favourable habitats (directed dispersal) • Colonize new habitats or regions (risk spreading)

  6. Costs of dispersal • Dispersal mortality • Reach less favourable habitats • Reduced local density (and competitiveness)

  7. Examples of dispersal • Seed dispersal • Wind, animals (fur, intestines), water, active self-dispersal (Impatiens spp.) • Dispersal across land surface (when continents where still together) • Animals „running, flying“ • Passive dispersal in animals: spiders (wind)

  8. Dispersalandthespatialdistributionofspecies

  9. Glanville fritillary butterfly on Åland Islands (SW Finland) http://www.helsinki.fi/science/metapop/Field_sites/Aland.htm

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