An analysis of variability in seed settling velocities of several wind-dispersed Asteraceae

Abstract

The author measured settling velocities on seeds of Aster exilis, Picris echioides, Chrysopsis villosa, Heterotheca grandiflora, Conyza bonariensis, Sonchus oleraceus, Senecio vulgaris and Taraxacum officinale, and estimated components of total variation in seed settling velocities due to differences among species, among plants within species, and among inflorescences and seeds within plants. Contrasts among mean settling velocities showed that the five introduced species have lower settling velocities than the three native species; this result continues to be true when annuals are considered separately from biennials and perennials. Also, over all species, annuals have lower settling velocities than biennials and perennials. Variability among species apparently reflects different dispersal "strategies'; these different strategies may be correlated with other life-history traits and with ecological characteristics. Variability within species may represent an example of risk- spreading. -from Author