First macrofossil record of Begonia (Begoniaceae)

Abstract

Premise of the study: Begonia is the sixth-largest genus of flowering plants, with about 1400-1500 species in 66 sections. Several species are popular with horticulturalists, mainly for their colorful flowers and leaves. However, the evolutionary history of the genus is debated, and until now there has been no macrofossil record. Here, we report on a fossil winged capsule from the Pliocene of Alabama and interpret it as a Begonia fruit, which represents the first convincing macrofossil evidence of the genus. Methods: Identification required extensive literature and herbarium searches to compare features of the fossil with those of ther recognized fossil and extant taxa that have winged fruits. Key results: The fossil is identified as a Begonia fruit on the basis of a combination of characters, including the presence of two unequally developed wings, at least one additional inferred wing, details of the wing venation, a prominent marginal vein, locule opening associated with a wing, and a persistent pedicel. Conclusions: Although too young to provide a calibration point for molecular divergence-time estimates, this fossil is noteworthy as the first macrofossil record of Begonia. It may represent a species that initially arrived from the south via Mexico after the closing of the Central American Straits. We propose that this fossil should stimulate a reexamination of other unidentified fossil winged fruits, as older records of Begonia may be forthcoming. © 2011 Botanical Society of America.