Abstract

The tropics are often evoked as a center for species origination. Foraminifera are one of the few groups of organisms with a fossil record sufficient to establish the geographic origin of species. The modern foraminiferal biota on the Atlantic continental margin of North America contains 259 species with a fossil record. The worldwide geographic origin of these species was documented using museum collections. Only 14% of these species originated in the subpolar regions, whereas nearly equal proportions originated in the temperate regions (46%) and tropical regions (40%). Moreover, the majority (76%) of species originating in the temperate regions now also occur in the modern tropical biota. These foraminiferal data suggest that, in contrast to the center of origin hypothesis, the biota of temperate and tropical latitudes act in concert with a substantial species interchange between them.

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