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What do we really know about extinction?

abstract1 (full description below): Pp. 111-124 in Schonewald-Cox, S. M. et al. (eds.) Genetics and Conservation. Addison-Wesley.
What do we really know about extinction?. PDF/Acrobat file     SoulĂ©, M. E.

Scores of birds, mammals, and flowering plants have suddenly become extinct, particularly on oceanic islands, during the last 1M) years. It is as if some epidemic were raging among these species. Now the disease appears to be spreading to the continents. You already know the pathogen-it is man. During the last few centuries Europeans have conquered, colonized, and cannibalized the planet's islands. They brought guns, clubs, rats, cats, dogs, mongooses, goats, pigs, weedy plants, diseases and exotic birds to help finish the job. The results are well known (recent reviews include those by Frankel and Soule, 1981; Myers, 1979; Ehrlich and Ehrlich, 1981b). What concrete conclusions about extinction have we assembled from these island die-offs? There are really only two (Frankel and Soule, 1981, Chapter 2). First, animals and plants, in adapting to islands that have few if any predators or herbivores, often change in ways that make them very susceptible to predation and herbivory. Birds tend to lose the ability to fly, and they also adopt ground nesting and foraging. Reptiles, birds, mammals lose their fear and flight reactions in the absence of predators. Plants also lose their defenses, (such as poisonous chemicals and spines) against herbivores (Culquist, 1974).