SECTION II POPULATION ECOLOGY A POPULATION IS A GROUP OF INTERBREEDING MEMBERS of a species. A number of more or less discrete subpopulations may be distributed over the geographic range of a species population. | SECTION II POPULATION ECOLOGY A POPULATION IS A GROUP OF INTERBREEDING MEMBERS of a species. A number of more or less discrete subpopulations may be distributed over the geographic range of a species population. Movement of individuals among these demes composing a metapopulation and newly available resources compensate for local extinctions resulting from disturbances or biotic interactions Hanski and Gilpin 1997 . Populations are characterized by structural attributes such as density dispersion pattern and age sex and genetic composition Chapter 5 that change through time Chapter 6 and space Chapter 7 as a result of responses to changing environmental conditions. Population structure and dynamics of insects have been the subject of much ecological research. This is the level of ecological organization that is the focus of evolutionary ecology ecological genetics biogeography development of sampling methods pest management and recovery of endangered species. These disciplines all have contributed enormously to our understanding of populationlevel phenomena. Abundance of many insects can change orders of magnitude on very short time scales because of their small size and rapid reproductive rates. Such rapid and dramatic change in abundance in response to often-subtle environmental changes facilitates statistical evaluation of population response to environmental factors and makes insects useful indicators of environmental change. The reproductive capacity of many insects enables them to colonize new habitats and exploit favorable conditions or new resources quickly. However their small size short life span and dependence on chemical communication to find mates at low densities limit persistence of small or local populations during periods of adverse conditions frequently leading to local extinction. Population dynamics reflect the net effects of differences among individuals in their physiological and behavioral interactions with the environment. Changes in .
