To investigate the persistence of figs and their short-lived pollinators in highly seasonal environments and in small populations, three native figs were studied near the edge of their range in Sonora, Mexico. The reproductive phenologies of Ficus insipida (Willd.) and F. petiolaris (H.B.K.) were contrasted between a drier site with small populations and a wetter site with large populations. In addition, F. pertusa (L.) phenology was censused in the wetter site and compared with findings from Central America, Trees from smaller populations in the drier site produced less synchronous crops. Individuals within populations became reproductively synchronized at the population level but rapidly attained asynchrony in the drier site because of a breakdown in within-tree crop synchrony. Sexual-phase overlap occurred in all species and sites. Intraspecific variation in reproductive phenology may explain the persistence of figs and fig wasps in highly seasonal environments and small populations.
Reports on the recovery of a Florida fig pollination mutualism devastated by Hurricane Andrew in August 1992. Damage to Ficus aurea included loss of all leaves and fruits and many branches, as well as the presumed local extinction of its pollinator Pegoscapus jimenezi. Within five months, however, fig flowering phenology and fig wasp abundance had recovered to near prehurricane levels. Unusual phenological traits of F. aurea may have aided in the rapid reestablishment of pollinator populations; also, the wasps may have previously underappreciated capacities for long distance movements. This study suggests that obligate interactions can be resilient to certain population-level catastrophes. -from Authors
PMID: 11375097;PMCID: PMC1088715;Abstract:
The over 700 species of Ficus are thought to have co-speciated with their obligate pollinators (family Agaonidae). Some of these wasp species pollinate figs actively, while others are passive pollinators. Based on direct observations of mode of pollination in 88 species, we show that mode of pollination can confidently be predicted from fig traits only (anther-to-ovule ratio) or from wasp traits only (presence of coxal combs). The presence of pollen pockets is not a predictor of mode of pollination. Data, direct and indirect, on 142 species, demonstrate numerous cases of the loss of active pollination and suggest one or few origins of active pollination. Hence, active pollination, an impressive example of the sophisticated traits that may result from mutualistic coevolution, depends on selective forces that can be overcome in some species, allowing reversions. Despite frequent loss, active pollination remains the predominant mode of pollination in Ficus.
The obligate pollinators of figs, 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. The authors have rejected the validity of this Seasonality Hypothesis for Ficus aurea near its northern range limit. Crops of individual trees were most, not least synchronous during the coldest, driest months of two years. Maximum asynchrony occurred in seasons that were probably most favourable for wasp transit between trees, but 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. -from Authors