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How the Red Queen Drives Terrestrial Mammals to Extinction

Science  19 Jul 2013:
Vol. 341, Issue 6143, pp. 290-292
DOI: 10.1126/science.1239431

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Background Extinction

Diversity results through both the processes of species origination and extinction. However, studies of extinction have tended to focus on mass extinctions, despite the fact that the background extinction represents a greater loss in terms of the absolute number of extinct taxa. In order to identify what factors affect this rate of background extinction, Quental and Marshall (p. 290, published online 20 June) explored the dynamics of 19 mammalian clades and compared the rates of expansions and declines among taxa to expected models assuming random processes. Most clades decline to extinction in a “driven” manner—that is, faster than expected by chance alone.

Abstract

Most species disappear by the processes of background extinction, yet those processes are poorly understood. We analyzed the evolutionary dynamics of 19 Cenozoic terrestrial mammalian clades with rich fossil records that are now fully extinct or in diversity decline. We find their diversity loss was not just a consequence of “gamblers ruin” but resulted from the evolutionary loss to the Red Queen, a failure to keep pace with a deteriorating environment. Diversity loss is driven equally by both depressed origination rates and elevated extinction rates. Although we find diversity-dependent origination and extinction rates, the diversity of each clade only transiently equaled the implied equilibrium diversity. Thus, the processes that drove diversity loss in terrestrial mammal clades were fundamentally nonequilibrial and overwhelmed diversity-dependent processes.

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