The relationship between seed size and establishment conditions in tropical hardwood hammocks of the Florida Keys

Background/Question/Methods

Seed mass is considered to be an important attribute for the establishment success of plant species, and propagule size may affect the likelihood of reaching a favorable microsite among species employing several dispersal mechanisms. The main objective of the study was therefore to examine the relationship between seed/propagule size and establishment conditions in woody species of tropical dry forests, as reflected in comparisons among tree species with differing resource requirement for establishment (e.g. light). In general, species that become established beneath a closed canopy are expected  to have higher fruit sizes or seed masses than species that require higher light. Species are divided into two types based their occurrence in forest age, early- and late-successional species. To test the hypothesis that seed/propagule masses of mature forests species are significantly larger than those of early-successional species, we compare fruit size and seed mass of tree species in south Florida hammocks.

Results/Conclusions

More than 80% of species in dry tropical forests of our Florida Keys study area had fleshy fruits and the remainder had dry fruits. Pioneer species have significantly lower seed mass than late-successional species (p-value=0.03), but average fruit sizes do not differ  between mature and young forest species. The relationship between seed size and establishment condition can be useful in understanding community assembly  rules, especially systems in which, large fruits and seeds are associated more closely with mammals and larger birds.