Traits of recalcitrant seeds in a semi-deciduous tropical forest in Panama: some ecological implications

1. We used cross-species and phylogenetic analyses to compare seed traits of 36 species with desiccation-sensitive and 189 with desiccation-tolerant seeds from a semi-deciduous forest in Panama. 2. When correcting for phylogenetic dependence between taxa, the desiccation-sensitive seeds were significantly larger than desiccation-tolerant seeds (3383 vs 283 mg) and typically shed during the wet (as opposed to dry) season. Both traits presumably reduce the rate of seed drying and hence the risk of desiccation-induced mortality for the desiccation-sensitive species. 3. Growing-house germination trials in simulated understorey and canopy gap environments revealed that the desiccation-sensitive species germinated most rapidly. Additionally, on a proportion basis, the desiccation-sensitive seeds allocated significantly less resources to seed physical defences (endocarp and/or testa) which may partially facilitate rapid germination. Both relationships were significant when correcting for phylogenetic dependence and seed mass. 4. Our results suggest that, for large-seeded species which will dry slowly, desiccation sensitivity may be advantageous. Rapid germination may reduce the duration of seed exposure to predation, and the low investment in physical defence means that, per unit mass, desiccation-sensitive seeds are a more efficient use of resources in seed provisioning.