Strong spatial and temporal limitations in seed arrival as complementary mechanisms for species coexistence in a tropical Atlantic coastal forest

Spatial limitation in seed arrival is pervasive among species in tropical forests and has been considered an important mechanism for species coexistence. Temporal limitation, when associated to a non-synchronous within-year pattern of seed arrival, could also contribute to species coexistence by diminishing encounter chances among species with distinct competitive abilities. However, temporal seed limitation (TSL) at the community level has been scarcely measured. Data from monitoring seed traps each month for three years in a subtropical Atlantic coastal plain forest in southeastern Brazil were used to evaluate if TSL could be an important mechanism structuring the community and if it was associated with an asynchronous pattern of temporal seed distribution. Furthermore, it was investigated if the values of spatial seed limitation (SSL) and TSL for each species were correlated and if some species traits could be used as a proxy for their SSL or TSL patterns. The SSL and TSL values were very high and strongly positively correlated, with 75% of the species found in less than four seed traps or three months each year. Within-year temporal seed distribution was clearly non-synchronous, but when compared to null models, there was no evidence of a deterministic process of temporal partitioning among species. Species with heavy seeds showed stronger SSL and TSL than species with light seeds. Our results suggest that high TSL associated with a non-synchronous temporal distribution could act as a complementary mechanism that structures this community by reducing encounter chances among species.