Interspecific variation in primary seed dispersal in a tropical forest

Abstract

Summary 1.We investigated the relationships of seed size, dispersal mode and other species characteristics to interspecific variation in mean primary seed dispersal distances, mean annual seed production per unit basal area, and clumping of seed deposition among 41 tropical tree species on Barro Colorado Island, Panama. 2. A hierarchical Bayesian model incorporating interannual variation in seed production was used to estimate seed dispersal, seed production, and clumping of seed rain for each species from 19 years of data for 188 seed traps on a 50-ha plot in which all adult trees were censused every 5 years. 3. Seed dispersal was modelled as a two-dimensional Student's T distribution with the degrees of freedom parameter fixed at 3, interannual variation in seed production per basal area was modelled as a lognormal, and the clumping of seed rain around its expected value was modelled as a negative binomial distribution. 4. There was wide variation in seed dispersal distances among species sharing the same mode of seed dispersal. Seed dispersal mode did not explain significant variation in seed dispersal distances, but did explain significant variation in clumping: animal-dispersed species showed higher clumping of seed deposition. 5. Among nine wind-dispersed species, the combination of diaspore terminal velocity, tree height and wind speed in the season of peak dispersal explained 40% of variation in dispersal distances. Among 31 animal-dispersed species, 20% of interspecific variation in dispersal distances was explained by seed mass (a negative effect) and tree height (a positive effect). 6. Among all species, seed mass, tree height and dispersal syndrome explained 28% of the variation in mean dispersal distance and seed mass alone explained 45% of the variation in estimated seed production per basal area. 7. Synthesis . There is wide variation in patterns of primary seed rain among tropical tree species. Substantial proportions of interspecific variation in seed production, seed dispersal distances, and clumping of seed deposition are explained by relatively easily measured plant traits, especially dispersal mode, seed mass, and tree height. This provides hope for trait-based generalization and modelling of seed dispersal in tropical forests.

The evolution of the competition–dispersal trade-off affects α- and β-diversity in a heterogeneous metacommunity

“…A comparison of traits assumed to be good proxies of dispersal, such as dispersal attributes of seeds in plant communities (see [40] for an example in grassland communities) might be a first approach to test this prediction. More refined statistical approaches based on dispersal kernel estimation [11,41] is a further possibility. A combination of genetic and demographic data collected in several species might also return relevant information on dispersal, as already done in metapopulations of single species [42].…”

“…Both empirical studies and field surveys suggest that these trade-offs are a distinctive characteristic of communities from many natural systems [9,10], and are sometimes associated with wide variation in dispersal among species belonging to the same community (e.g. [11] for the tree community of Barro Colorado Island). However, whether (and how) they affect patterns of species diversity in natural communities remains debatable [12,13].…”

Forest tree neighborhoods are structured more by negative conspecific density dependence than by interactions among closely related species

“…1). Forest trees begin reproducing at relatively large sizes, levels of seed production tend to increase with tree size, and seed dispersal distances are limited with most seeds landing near their seed-bearing parent (Howe and Smallwood 1982, Wright et al 2005, Muller-Landau et al 2008). Limited seed dispersal will contribute to negative relationships between focal tree size and ADT_all because conspecific neighbors have evolutionary divergence times of zero; however, seed dispersal should have no effect on the relationship between focal tree size and phylogenetic neighborhood composition when only heterospecific neighbors are considered (i.e., ADT_hetero; Fig.…”

“…It is well established that seed dispersal is limited for forest trees (Muller-Landau et al 2008) and should act to reduce the average divergence time of neighbors by concentrating conspecifics around larger focal trees (Fig.1a).…”

Comparing and contrasting flooded and unflooded forests in western Amazonia: seed predation, seed pathogens, germination

“…This suggests that other mechanisms or other sources of variation in the workings of the seed mechanisms and tolerances may play major roles in rainforest recruitment and regeneration (Muller-Landau et al 2008). Indeed the complexities of forest recruitment are a major challenge for modelers who wish to predict plant-plant replacements (Myster 2012b).…”