FOSSIL WIND-DISPERSED FRUITS AND SEEDS FROM THE PALEOCENE OF COLOMBIA AND THEIR IMPLICATIONS FOR EARLY NEOTROPICAL RAINFORESTS

Extant Neotropical rainforests are well known for their remarkable diversity of fruit and seed types and varied dispersal syndromes. Among angiosperms, biotic dispersal greatly overshadows abiotic mechanisms (wind or aquatic dispersal) in extant Neotropical rainforests. Many important plant families in Neotropical rainforests (e.g. Apocynaceae, Bignoniaceae, Bromeliaceae, Sapindaceae, etc.) include abundant genera with various morphological adaptations for wind dispersal of fruits or seeds, such as wings, accessory hairs, or reduced size. Most of these families have moderate to high levels of plant diversity in extant Neotropical rainforests, where they commonly occupy the upper levels of the canopy. It is still unknown when these groups appeared in the Neotropical fossil record. Thirty-five specimens were collected from the Paleocene of Colombia (~58-60 Ma). We surveyed the fruit and seed morphology of abundant wind-dispersed angiosperm families and reviewed the related fossil record. Six new species of disseminules with varied adaptations for wind dispersal are documented here. These fossils, representing extinct genera of Ulmaceae, Malvaceae, and other uncertain families, suggest that wind-dispersed fruit and seed syndromes were already common in the Neotropics by about 58-60 My ago, coinciding with the early development of multistratal rainforests. Although the major families known to include most of the winged-dispersed disseminules in extant rainforests are still missing from the Paleogene fossil record of South and Central America, the new fossils imply that disseminules transported via wind currents were a relatively important mechanism of plant evolution and diversification in ancient Neotropical rainforests.