Subannual phenology and the effect of staggered fruit ripening on dispersal competition

<p>Seed dispersal mutualisms evolve in complex communities of plants and frugivorous animals, within which indirect interactions such as competition and facilitation can occur. Many tropical plants reproduce subannually in multiple episodes per year. Yet, the consequences of episodic reproduction on interactions with seed dispersers remains largely unexplored. We studied <em>Guarea guidonia</em> (<em>Meliaceae</em>), a subannually reproducting tree, to examine temporal variation in seed dispersal within a tropical forested landscape in the central Dominican Republic. We hypothesized that foraging by seed dispersers would (a) increase with daily ripe fruit set on focal trees, (b) decrease with increasing ripe fruit biomass of neighboring plants, and (c) decrease in response to the fruiting periods of other taxa at the landscape scale. Over 18 months, we tracked the phenology of 24 focal trees and quantified foraging during fruiting phases through repeated observations, simultenously measuring seed dispersal in traps beneath isolated perches across the study landscape. Date was the only clear predictor of frugivore visitation, with early and late peaks in activity during the 5-month fruiting period. The midseason decline in foraging at focal trees matched a decline in <em>Guarea</em> dispersal to seed traps independently of fruit abundance. Declines in foraging associated with <em>Guarea</em> were inversely related to peak dispersal of higher quality lipid-rich fruiting species. Our results suggest that multiple flowering episodes and subsequent asynchronous fruit ripening of low-quality fruits can reduce competititive pressure from other high quality fruiting species, implying that this potentialy bet-hedging strategy may be an overlooked factor in the evolution of subannual reproduction.</p>