BLOWING IN THE WIND: ABIOTIC DISPERSAL, ECOLOGY, AND PHYLOGENY IN SOUTH AMERICAN TERTIARY FLORAS

Wind dispersal of reproductive propagules is employed worldwide by a wide variety of extant plant lineages across many habitats. Wind dispersal, although rarely a directional means of distancing progeny from parents, is none-the-less an effective and reliable means of dispersal away from the parent plant. Elaboration of asymmetrically winged fruits or seeds allows increased horizontal movement of a dispersal unit, relative to those with a symmetrical wing, by creating an auto-gyro. Three angiosperm families of Andean plants are well represented in the fossil record by asymmetrically winged fruits and are used to illustrate the application of fossil plant remains to dispersal biology, ecology, and phylogenetic reconstruction. Data from remains of sub-Andean (lower montane) floras from Bolivia and Ecuador of late Tertiary age (Miocene and Pliocene) are presented. Fossil genera represented as winged fruits include Ruprechtia (Polygonaceae), Tipuana (Fabaceae), and Loxopterygium (Anacardiaceae). Ecological reconstructions based on leaf morphology alone can be refined by using the temperature, elevation, and precipitation limitations of modern representatives of the fossil fruit genera as constraints on the ecological distribution of the fossils. The abundance of winged fruits in lacustrine deposits does not correlate with abundance of the source trees in the surrounding paleovegetation, but the diversity (species richness) of winged dispersal units does allow extrapolations about the degree of seasonality and vegetation structure. Each of the illustrated dispersal units put temporal constraints on the structure of phylogenetic trees and thus have significant systematic utility.