POPULATION ECOLOGY

study of the processes that affect the distribution and abundance of animal and plant populations. A population is a subset of individuals of one species that occupies a particular geographic area and, in sexually reproducing species, interbreeds. The geographic boundaries of a population are easy to establish for some species but more difficult for others. For example, plants or animals occupying islands have a geographic range defined by the perimeter of the island. In contrast, some species are dispersed across vast expanses, and the boundaries of local populations are more difficult to determine. A continuum exists from closed populations that are geographically isolated from other populations of the same species to open populations that show varying degrees of connectedness. John N. Thompson Additional reading Eric R. Pianka, Evolutionary Ecology, 5th ed. (1994), provides a clear treatment of the basics of population ecology. Peter W. Price, Insect Ecology, 2nd ed. (1984), is a comprehensive text on the ecology of the most diverse group of organisms on Earth. Two books that examine the dynamics of plant populations and the evolution and ecology of plant life histories are Michael J. Crawley (ed.), Plant Ecology (1986); and Jonathan W. Silvertown and Jonathan Lovett Doust, Introduction to Plant Population Biology, 3rd ed. (1993). Michael Begon and Martin Mortimer, Population Ecology: A Unified Study of Animals and Plants (1986), examines the range of ecological and genetic factors that influence the structure, growth, and dynamics of populations. Thorough treatments of the theory of how genetic variation arises within populations and changes over time can be found in Daniel L. Hartl and Andrew G. Clark, Principles of Population Genetics, 2nd ed. (1989); and John Maynard Smith, Evolutionary Genetics (1989). One of the most detailed studies ever made of the population ecology and genetics of a vertebrate species is reported in B. Rosemary Grant and Peter R. Grant, Evolutionary Dynamics of a Natural Population: The Large Cactus Finch of the Galpagos (1989). Leslie A. Real (ed.), Ecological Genetics (1994), discusses the ways in which ecological conditions influence the genetic and spatial structure of populations and the life histories of organisms. Ian Newton (ed.), Lifetime Reproduction in Birds (1989), is a collection of long-term studies on the life histories and population ecology of birds. Richard B. Primack, Essentials of Conservation Biology (1993); and Michael E. Soul (ed.), Conservation Biology: The Science of Scarcity and Diversity (1986), apply the principles of population genetics, population ecology, and evolutionary biology to the conservation of populations.J.A. Drake et al. (eds.), Biological Invasions: A Global Perspective (1989), contains articles on the growth and dynamics of populations of species introduced into areas in which they are not native. Paul R. Ehrlich and Anne H. Ehrlich, The Population Explosion (1990), examines the problems of overpopulation and also offers solutions. Michael Gilpin and Ilkka Hanski (eds.), Metapopulation Dynamics: Empirical and Theoretical Investigations (1991), explores the importance of metapopulation structure to population dynamics and to interactions between species. John N. Thompson