Seed and fruit tradeoffs - the economics of seed packaging in Amazon pioneers

Background: The tradeoff between seed mass and seed number per plant is widely established for different taxa, guilds, and communities. Relative to primary forest species, pioneer species generally produce large numbers of small seeds. Aims: We tested if the relationship between seed mass and seed number was connected to the fruit variables - namely, fruit mass and fruit number per tree - in order to evaluate tradeoffs in seed packaging. Methods: Seed mass and seed number per tree as well as fruit mass and fruit number per tree were measured for 12 pioneer species common to secondary forests in the central Amazon. Results: Seed mass, seed number, fruit mass, and fruit number varied by several orders of magnitude among species. Seed number was explained only partially by seed mass alone (R-2 = 0.55), but nearly completely by the combination of seed mass, fruit mass and fruit number (R-2 = 0.94). The number of seeds per fruit was positively correlated with fruit mass and total seed number per tree and negatively with seed mass and fruit number. Seedling and adult abundances were most dependent on fruit number and fruit mass, not seed number and seed mass. Conclusions: Biomass tradeoffs between seed mass and seed number are partially dependent on seed packaging, specifically seeds per fruit, fruit mass and fruit number per tree for pioneer trees in the central Amazon.