Biogeografia funcional de sementes de gêneros arbóreos de terra firme da Amazônia

Abstract

The optimal size for a seed is influenced by wide range of factors, such as dispersal strategy, germination strategy, degree of competition among seedlings, the constraints imposed by a particular growth form and the prevailing biophysical environment. Despite the complexity and interacting nature of these forces, systematic variation in seed mass has been observed at a macrogeographic scale in relation to latitude, net primary productivity, temperature, precipitation, and leaf area index. Here, we use a combination of GBIF records, climatic data from BIOCLIM and seed size categories derived from the literature to investigate potential relationships between seed size and biophysical variables at the biome scale in Amazon forest tree genera. Specifically, we tested the hypotheses that seed size would show associations with precipitation, temperature and seasonality. As predicted, tree genera with very small seeds were associated with lower precipitation, lower temperatures and higher seasonality, the opposite patterns being observed for trees with large seeds. These correlations remained when the numerically dominant (and ecologically specialised) Fabaceae were removed from the analysis. Our results are broadly consistent with the ‘recruitment hypothesis', which predicts that large seeds have a competitive advantage in closed canopy forest vegetation.