9 - Paleobiogeography and metatherian evolution  pp. 407-428

Paleobiogeography and metatherian evolution

By Frederick S. Szalay

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Nowhere in biology is the misleading and arbitrary use of ‘parsimony’ so disabling as in vicariance and panbiogeography, with their determined exclusion of virtually all biological data on vagility, reproductive strategy, niche-width, and so on.

Kirsch (1990, p. 162)

I have attempted to sketch how these oppositions (selection v. orthogenesis, ecology v. history) might be resolved if dichotomous views of causation are abandoned for a more complex view emphasizing interacting mutually contingent networks of causes. In practice achieving such a synthesis will require a breakdown of the conceptual and methodological boundaries between biogeography, evolutionary biology, systematics, ecology and geology.

Gray (1989, p. 804)

Few constraints limit and guide the nature of macro-and megaevolutionary patterns of terrestrial organisms as decisively as the nature of distribution, isolation, and connectedness of various land masses. Such important geographic factors are partly behind climatic and subsequently the environmental change that drives faunal extinctions and new ecological opportunities through ecological release (Van Valen, 1978), in other words opportunitybased adaptive evolution. These are some of the reasons why few subjects have engendered as much interest in a wide variety of subdisciplines of natural history as the geographic enigma of marsupial distribution and evolution through time and space. Given the background of the Cretaceous spread of the angiosperms (Brenner, 1976) and the faunal upheavals at the beginning and end of the Eocene in the northern hemisphere (Stucky, 1990; Krause & Maas, 1990, etc.) the occurrence of marsupials in space and time has been one of the knottiest of puzzles in mammalian paleobiogeography.