GLOBAL PATTERNS OF PRE-DISPERSAL PROPAGULE PREDATION IN MANGROVE FORESTS

Mangroves in disparate families produce viviparous seedlings (propagul es) that are attacked by many crab and insect predators both before an d after dispersal. While post-dispersal predation is viewed as an impo rtant factor in structuring many mangrove communities, pre-dispersal p redation rates and agents have been characterized for few species. Ten species of mangrove and 3299 propagules were surveyed for pre-dispers al propagule predation at 42 sites around the world. Pre-dispersal pre dation rates were variable among sites and species, ranging from 0 to 93 percent within stands, with a global total predation rate of 23.3 p ercent (across all propagules examined) and a mean level of 28.3 perce nt across sites. Grapsid crabs, Coleoptera and Lepidoptera were the pr imary predators identified. Forests near human population centers and stands occurring at high intertidal sites exhibited higher levels of p ropagule predation than those in unpopulated or low-intertidal sires. Predation rates on a species were weakly, negatively correlated with c onspecific seedling density at a sire. To explore temporal variation i n, and ramifications of pre-dispersal predation for propagule growth a nd abscission dynamics, Rhizophora mangle propagules were monitored ov er two years at three sires in Belize, Central America. Predation did not significantly reduce hypocotylar growth of germinated propagules o n the parent tree, but nearly doubled the abscission race of premature propagules. Pre-dispersal propagule predation is a ubiquitous feature of mangrove forests world-wide, and must be accounted for in estimate s of reproductive output, stand health, and propagule availability for forestry and restoration efforts.