Transcript Chapter 7: Modeling the Geographical Spread of Invasive Species

Chapter 7: Modeling the
Geographical Spread of Invasive
Species
By Marieke Kester and Carla
Severe
General Overview
Geographical spread: expansion and
establishment
– Expansion from a focal point
– Establishment within non-native range
• Why have geographical spread models?
– To test system knowledge
– Used as a filter
– To focus on troublesome components
• Knowledge deficits
• Oversimplification
• Lack of field data
Goals of modeling:
• Anticipate which non-native species will quickly
spread over considerable areas and which will
not
• Pinpoint the life history or ecological conditions
that are most important in allowing rapid range
expansion
• Prioritize control efforts
• Target management efforts towards halting or
slowing the rate of spread in an efficient and
effective manner
Reaction-diffusion equation
Rate of change of
Population density
=
Reaction to
population +
size
Diffusion
movement
Muskrat
• Propagule size (1909)= 5
• 50 years later: occupied
all of Europe
• Successfully eradicated
in Britain and Scotland
• How do you think they
eradicated the muskrats?
Does this dispersion picture follow the reaction-diffusion
model?
What species follow a leptokurtic dispersal curve vs. a
normal curve?
• Are there any species for which the
reaction-diffusion model is accurate?
• What the limits and benefits of the
reaction-diffusion model?
 The reaction diffusion model
underestimates the spread of terrestrial
species, but overestimates the spread of
marine species. Why?
• The diffusion coefficient requires a number
of marked individuals to be recaptured.
Can this be adapted to work for plants?