Causes and Consequences of Within-Tree Phenological Patterns in the Florida Strangling Fig, Ficus aurea (Moraceae)

Abstract

The obligate pollinators of figs (Ficus, Moraceae), species-specific agaonid wasps, benefit figs only by transporting pollen between trees; larvae are seed predators. But given the high risk of mortality in flight between trees, adult wasps should prefer to pollinate and oviposit within inflorescences (syconia) at the same tree at which they developed. Flowering within individuals is tightly synchronous in most species, while different trees flower out of phase with each other, suggesting that fig phenology has evolved to assure outcrossing. However, some fig species show distinct within-tree flowering asynchrony. It has been suggested that such asynchrony is an adaptation by which figs in seasonal environments can reduce pollinator mortality, by permitting wasps to persist on individual trees at times when flight would be impossible. We have evaluated and rejected the validity of this Seasonality Hypothesis for the Florida strangling fig, Ficus aurea, near its northern range limit. Crops of individual trees were most, not least, synchronous during the coldest, driest months of 2 years. Maximum asynchrony occurred in seasons that were probably most favorable for wasp transit between trees. However, temporal overlap of the phenological stages that permit wasps to remain on their natal trees was always very rare, implying that consecutive cohorts of developing syconia may be spaced in time to limit this occurrence. We suggest alternative costs and benefits for these phenological traits, as well as the proximate mechanisms that might produce them.