Krebs (1972:139)
- "a group of organisms of the same species occupying a particular space at a particular time."
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."
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
1. Population processes
a. birth
b. death
c. immigration (ingress)
d. emigration (egress)
2. Population characteristics
a. size
i. abundance
ii. density
iii. total numberb. composition
i. sex ratio
ii. age distribution
iii. gene frequencies
iv. physiological statec. distribution
i. pattern
ii. scale
d. movement
i. migratory - anadromous
ii. nonmigratory3. "Environment"
a. food
b. cover
c. water conditions
d. nest sites
e. disease
f. predators
g. competitors
h. weather
4. Interactions
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
1. Significance of the problem:
- 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.
2. Concepts (Hierarchical Aggregations)
Deme - a group of individuals more genetically similar to each other than to other individuals (Wells and Richmond 1995). Continous distribution geographically. One "patch" of habitat.
Population - A collection of demes with strong connections between adjacent demes, i.e., high rates of disperal and high correlations in demographic rates between adjacent demes. Geographically a collection of patches without great expanses of nonhabitat intervening.
- Metapopulation - a collection of populations in scattered habitat patches separated from each other by nonhabitat (Levin 1970). Possible low correlations in demographic rates and possible low rates of dispersal. Populations may act as possible sources for recolonization.
Subspecies population - 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 nonhabitat.
Species population - 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.
3. Steps to delimit a population unit:
(1) State objectives clearly.
(2) Determine distribution.
(3) Determine patterns of movement and barriers to movement.
(4) Determine levels of genetic/phenotypic similarity among subunits.
(5) Identify associations in demographic rates between subunits.
(6) Integrate all this information to outline the most discrete unit(s) possible, which still meet(s) objectives.
4. Unit Stock (see Cushing 1981:49-70)
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.
Caughley, G. 1977. Analysis of vertebrate populations. John Wiley and Sons, New York. pp. 1-7.
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