Intraspecific variation in seed dispersal of a Neotropical tree and its relationship to fruit and tree traits

• Published in: Ecology and evolution Vol. 6; no. 4; pp. 1128 - 1142
• Main Authors: Augspurger, Carol K., Franson, Susan E., Cushman, Katherine C., Muller‐Landau, Helene C.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-02-2016; John Wiley and Sons Inc
• Subjects: Abscission; Correlation analysis; Crown area; crown height; Descent; Diaspore; Dispersal; Dispersion; functional traits; Original Research; Parents; Parents & parenting; recruitment; Seed dispersal; seed shadow; Seedlings; Seeds; tails of distribution; Variation; Wind; wind dispersal; wing loading; wind dispersal; crown height; tails of distribution; recruitment; functional traits; seed shadow; Crown area; wing loading
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.1905

The distribution of wind‐dispersed seeds around a parent tree depends on diaspore and tree traits, as well as wind conditions and surrounding vegetation. This study of a neotropical canopy tree, Platypodium elegans, explored the extent to which parental variation in diaspore and tree traits explained (1) rate of diaspore descent in still air, (2) distributions of diaspores dispersed from a 40‐m tower in the forest, and (3) natural diaspore distributions around the parent tree. The geometric mean rate of descent in still air among 20 parents was highly correlated with geometric mean wing loading1/2 (r = 0.84). However, diaspore traits and rate of descent predicted less variation in dispersal distance from the tower, although descent rate−1 consistently correlated with dispersal distance. Measured seed shadows, particularly their distribution edges, differed significantly among six parents (DBH range 62–181 cm) and were best fit by six separate anisotropic dispersal kernels and surveyed fecundities. Measured rate of descent and tree traits, combined in a mechanistic seed dispersal model, did not significantly explain variation among parents in natural seed dispersal distances, perhaps due to the limited power to detect effects with only six trees. Seedling and sapling distributions were at a greater mean distance from the parents than seed distributions; saplings were heavily concentrated at far distances. Variation among parents in the distribution tails so critical for recruitment could not be explained by measured diaspore or tree traits with this sample size, and may be determined more by wind patterns and the timing of abscission in relation to wind conditions. Studies of wind dispersal need to devote greater field efforts at recording the “rare” dispersal events that contribute to far dispersal distances, following their consequences, and in understanding the mechanisms that generate them.
Variation in fruit traits among 20 parents of Platypodium elegans, a wind‐dispersed tropical canopy tree, explained descent rate in still air, which predicted dispersal distance from a forest tower. Saplings of six parents were heavily concentrated in the 95th percentiles of seed shadow distributions. Variation among parents in these distribution tails are likely determined by wind conditions as they could not be explained by fruit or tree traits.