ATBC 2012 49th Annual Meeting Bonito-MS, Brasil
FS06.OC.01 Seed and fruit tradeoffs – the economics of seed packaging in Amazon pioneers Bentos T1, Mesquita R1, Camargo J2, Williamson B - 1National Institute for Research in the Amazon (INPA) - Dept. of Research in Ecology, 2National Institute for Research in the Amazon (INPA) - Biological Dynamics of Forest Fragments Project The tradeoff between seed mass and seed number per tree has been widely established for different communities and is interpreted as a tradeoff between establishment and dispersal. Here, we analyze tradeoffs among seed and fruit traits of Amazon pioneer tree species as the economics of seed packaging. We hypothesized that seeds per fruit is the pivotal variable such that for a given fruit mass, more seeds per fruit implies lower seed mass which fosters greater seed number per tree. Similarly, for a given seed mass, more seeds per fruit implies greater fruit mass which is associated with lower fruit number per tree. We tested and generally confirmed these relationships for seed and fruit data from 12 species of pioneer trees from the Central Amazon. Notably, seed number was explained only partially by seed mass (R2 = 0.55), but nearly completely by seed mass, fruit mass and fruit number (R2 = 0.94). In addition, we measured seedling densities in light gaps and adults in secondary forests and then used regression analysis to determine if seedling and adult densities could be explained by seed packaging variables, by fruiting duration, or by germination rates. Seedling and adult densities were best explained by fruit number and fruit mass, not by seed number and seed mass. Fruit variables may be more predictive of seedling and adult densities than seed variables if dispersal is more limiting than establishment. The seed mass-seed number tradeoff in plants, generally interpreted as a tradeoff between dispersal and establishment, is only one component of the economics of seed packaging—i.e., how biomass is allocated among both seed and fruit traits across coexisting plant species.
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