Transcript Day1

Dispersal Models
Module B2 Spatial Modelling in Ecology, 5 ECTS
Develop programming skills
Implement, apply and critically assess computer models
Understand the role of spatial processes for ecosystem dynamics
Confronting models with data
Implement, apply and critically assess computer models
Importance of dispersal for migration and population persistence
Approaches to modelling dispersal:
Long-distance dispersal
Fitting dispersal models to data
Individual-based (e.g. random walk)
Dispersal kernels (e.g. diffusion)
Network approaches
Computer exercises - Programming (R language) - (group work)
Literature study
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)
• What is dispersal?
• How does dispersal affect the spatial
distribution of populations?
– Metapopulation models
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
• 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
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, namely immigration and
Schurr, Frank (2005), PhD thesis, p. 1
Benefits of dispersal
• Offspring survival is often (but not always)
higher away from the parent (densitydependent predation or pathogens;
competition with adults)
• Reach favourable habitats (directed dispersal)
• Colonize new habitats or regions (risk
Costs of dispersal
• Dispersal mortality
• Reach less favourable habitats
• Reduced local density (and competitiveness)
Examples of dispersal
• Seed dispersal
– Wind, animals (fur, intestines), water, active selfdispersal (Impatiens spp.)
• Dispersal across land surface (when continents
where still together)
• Animals „running, flying“
• Passive dispersal in animals: spiders (wind)
Dispersal and the spatial distribution
of species
Glanville fritillary butterfly on Åland Islands (SW Finland)