NATR 320 Lecture Notes - Lecture 8: Ideal Free Distribution, Lodoicea, Metapopulation
22 May 2020
School
Department
Course
Professor
Michael Le
Arc
NATR 320
Principles of Ecology
● Measuring dispersion
○ Movement of individuals from one area to another
■ Often, “natal dispersal” (displacement of offspring from parents)
○ NOT the same as seasonal migration
○ Can lead to colonization of new areas
○ Avoid predation, competition, inbreeding
○ Dispersal limitation can constrain geographic ranges
■ The double coconut, endemic the Seychelles
■ Dandelions found all continents except Antarctica
o Dispersal limitation might explain why
A. Polar bears do not live in the Antarctic
B. Wildebeests migrate on an annual cycle, but locusts migrate only when conditions
require it
C. Tuna do not live in Lake Michigan (tuna require salt)
D. The northern limit of palms in North America corresponds with the frequency of
freezing nights in the winter
● Population isolation and meta-population structure
○ Population structure: subdivision of organisms into subpopulations living in a suitable
patches of habitat surrounded by matrix (unsuitable habitat)
● Models of spatial structure
○ Metapopulation Model
■ Metapopulation: set of populations or subpopulations of a
species, linked by dispersal
■ Basic metapopulation model: suitable habitat patches (equal quality) embedded
within a matrix of unsuitable habitat
● Proportion of patches occupied reflects colonization and extinction
● Assume patches are at the same quality level
○ Source-sink Model
■ All habit patches are not created equal!
■ Sources: high quality habitat and (+) population growth without emigration -
provide dispersers
■ Sinks: poor quality habitat and (-) population growth without immigration - rely on
dispersers
○ Why would you choose the “worse” habitat? Depends on competition
■ Quality of area declines as more inhabitants are there so the originally poor patch
is better
o Ideal free distribution: individuals distributed among different habitats
Document Summary
Movement of individuals from one area to another. Often, natal dispersal (displacement of offspring from parents) Can lead to colonization of new areas. Dandelions found all continents except antarctica: dispersal limitation might explain why. Population isolation and meta-population structure freezing nights in the winter. Population structure: subdivision of organisms into subpopulations living in a suitable patches of habitat surrounded by matrix (unsuitable habitat) Metapopulation: set of populations or subpopulations of a species, linked by dispersal. Basic metapopulation model: suitable habitat patches (equal quality) embedded within a matrix of unsuitable habitat. Proportion of patches occupied reflects colonization and extinction. Assume patches are at the same quality level. All habit patches are not created equal! Sources: high quality habitat and (+) population growth without emigration - provide dispersers. Sinks: poor quality habitat and (-) population growth without immigration - rely on dispersers. Quality of area declines as more inhabitants are there so the originally poor patch is better.
