Webster's Third New International Dictionary -
"The total number or amount of things especially within a given area."
"The organisms inhabiting a particular area or biotype."
"A group of interbreeding biotypes that represents the level of organization at which speciation begins."
Krebs (1972:139)
- A group of organisms of the same species occupying a particular space at a particular time.
La Monte Cole (1957)
- A biological unit at the level of ecological integration where it is meaningful to speak of birth rate, death rate, sex ratios, and age structure in describing properties or parameters of the unit.
1. Biome
2. Landscape
3. Ecosystem
4. Community
5. Population
6. Individual
7. Organ
8. Cell
Deme - A group of individuals were breeding is random. Continuous distribution geographically. One "patch" of habitat.
Population - A collection of demes with strong connections between adjacent demes. Geographically a collection of patches without great expanses of non-habitat intervening. Genetically closely related. High rates of dispersal between demes. High correlations in demographic rates between adjacent demes.
Metapopulation - A collection of populations. Possible low correlations in demographic rates (which produces high levels of independence). Possible low rates of dispersal (which can produce genetic differences). Populations may act as possible sources for recolonization.
Subspecies - A collection of metapopulations in a region. Very rare dispersals maintain genetic similarity. Demographic independence may be nearly complete. Occupied patches may be separated by large areas of non-habitat.
Species - The collection of subspecies encompassing the entire distribution of the species. Defines the entire geographic range of the species. May encompass substantial differences in phenotypes (habitat, physiology, behavior) and genotypes.
Species: presence-absence
Subspecies: relative abundance
Metapopulation: density
Population: survival, fecundity
Deme: immigration/emigration
First step in making statements and predictions about a population is to delimit the population unit.
Goal is to delimit a population unit that is as discrete as possible but which still meets your research/management objectives.
Ideally, chances of mating within this unit should be randomly distributed.
State objectives clearly.
Determine distribution.
Determine patterns of movement and barriers to movement.
Determine levels of genetic/phenotypic similarity among subunits.
Identify associations in demographic rates between subunits.
Integrate all this information to outline the most discrete unit(s) possible, which still meet(s) objectives.
Cushing (1981)
Many fish do not disperse.
Approaches:
Ricker (1972)
"During the first 30 years or so of this century it was customary to regard all populations of a fish species as more or less uniform, at least in respect to biologically important particulars. Observed differences between stocks were ascribed to differences in their environments."
What is a "stock"?
A group of fish spawning in a particular lake or stream at a particular season, which to a substantial degree do not interbreed with any other such group.
ESU
Evolutionary Significant Unit
Endangered Species Act requires protecting a population if it is an ESU.
ESU criteria:
Reproductively isolated from other conspecific population units.
Represents an important component in the evolutionary history of a species.
Implications of "Unit Stock" Concept:
Provides genetic perspective.
Two key concepts: (a) fish are subdivided into local populations, and (b) genetic differences between local populations are adaptive.
Cause: heterogeneity of resources.
Selective processes are most effective if populations are subdivided in local populations (Sewall Wright 1929).
Dispersal does not equal gene flow necessarily.
Ricker (1972) concluded that most transplants with salmonids reduced survival to maturity.
Maximum production from a complex of stocks with local adaptation of subpopulations.
Stock Differentiation:
- Population parameters
- Marking
- Physiological/behavioral characters
- Morphometric/meristic characters.
- Calcareous structures.
- Cytogenic characters.
- Biochemical characters.
- Immunogenetics.
- DNA
Population processes
a. birth
b. death
c. immigration (ingress)
d. emigration (egress)Population characteristics
a. abundance
b. composition (e.g., sex and ratios)
c. distribution (pattern, scale)
d. movement (migratory, nonmigratory)"Environment"
a. food
b. cover
c. water conditions
d. nest sites
e. disease
f. predators
g. competitors
h. weatherInteractions
a. within a population
b. between populations
c. between populations and environment
1. Endangered or rare species
2. Harvested species
3. Controlling harmful species
4. Predicting changes in non-harvested populations
The following list very briefly outlines the contribution of some early demographers to the understanding of population processes. You will note that at least three fundamental concepts were soon recognized: |
- There is a marked tendency for population to increase.
- Increase tends to be prevented by certain limiting factors acting on birth and death rates.
- Population processes are influenced by crowding; i.e., there are density effects.
a. Integrated previous views and popularized them.
b. Focused problems.
c. Human population was increasing exponentially while food was increasing arithmetically:
d. Influenced Darwin's thinking.
Adams, L. 1970. Population ecology. Dickenson Publ. Co., Inc. Belmont, California. pp. 1-7.
Begon, M. and M. Mortimer. 1981. Population ecology. Sinauer Assoc., Inc., Sunderland, Mass. 296pp.
Begon, M., J. L. Harper and C. R. Townsend. 1996. Ecology: Individuals, populations and communities. 3rd ed. Blackwell Scientific Ltd., Cambridge, Mass. 1068pp.
Caughley, G. 1977. Analysis of vertebrate populations. John Wiley and Sons, New York. pp. 1-7.
Cushing, D. H. 1981. Fisheries biology: a study of population dynamics. University of Wisconsin Press, Madison. (on reserve at library)
Hutchinson, G. E. 1978. An introduction to population ecology. Yale Univ. Press, New Haven, Conn. pp. 1-21.
Quick, H. 1974. Population ecology. Pegasus. Indianapolis. 185pp. Preface ix-xi.
Voute, A. D. 1970. in Osterbech, ed. Adv. Inst. Dynamics Numbers Pop.. pp.19-29.
Revised: 25 August 2011