Migration: A periodic mass movement of individuals from one place and climate to another.
Dispersal: The spreading or movement of individuals away from others.
Natal dispersal - dispersal from place of birth
Successful dispersal - dispersal that results in successful breeding in another population
Immigration: Dispersal into a population
Emigration: Dispersal out of a population
Important questions for population ecology:
What is the effect of immigration and emigration on local population parameters (e.g., abundance, population structure)?
What effect does dispersal rates have on metapopulation dynamics (e.g., persistence)?
What are the genetic consequences of dispersal among metapopulations, subspecies, and species?
Because of difficulties in measuring dispersal, analyses of populations typically ignore dispersal, assume that it does not exist or hope that immigration and emigration cancel out.
Three approaches have been used including:
Observations of marked animals (e.g., telemetry, intensive observations, trapping) that can then be fit to a parametric model
Mark-recapture studies that can estimate losses or gains to the population between trapping occasions
Recent genetic techniques that can be used to infer rates of successful dispersal between populations
Open population models (e.g., Jolly-Seber)
Tag-recovery studies: common in fisheries and ornithology
Dispersal and consequent establishment are often essential for metapopulation persistence
Population Sources: Net exporter of individuals.
Population Sinks: Net importer of individuals.
Genetic Approaches:
Assumption: The more genetic differentiation there is among populations, the less successful dispersal occurs among the populations
Fst: Method for estimating gene flow among populations
III. POPULATION STRUCTURE
A. Sex
B. Age
C. Size
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Revised: November 01, 2004