When Figs Wait for Pollinators: The Length of Fig Receptivity

Abstract

In plant species with an obligate species‐specific pollinator, gamete encounter is a critical phase in the success of reproductive strategies. One of the key factors in the success of gamete encounter, the length of female receptivity, has been rarely studied experimentally. In Ficus species (Moraceae), each exclusively associated with its specific pollinating wasp, the receptive female phase of individual syconia was believed to last only a few days. This estimate, based on field observations of pollinator arrivals, neglected the possibility that unpollinated syconia may remain receptive for a prolonged period. In two distantly related fig species (F. carica and F. aurea), we measured experimentally the duration of receptivity of individual syconia protected from pollinator visits. For these two species, receptivity lasted from 2 to 3 wk. Syconia pollinated at any time during this period of receptivity are capable of setting seeds. Furthermore, it has been assumed that female syconium receptivity stops quickly after pollinator visitation. Our experiments showed that syconia of both species are able to extend their receptive period for a few days longer when visited only by a single wasp. The demonstration of a long duration of female receptivity has important consequences for understanding the maintenance of the fig‐wasp mutualism.

Variation in reproductive output of Ficus superba despite aseasonal reproduction

“…Variable availability of pollinator is suspected to be the cause of the discrepancy, as earlier studies have shown that the duration of Phase B could be extended by 2-3 weeks in the absence of pollinators (Bronstein 1988, Khadari et al 1995, Ansett et al 1996a, while receptive syconia were observed to persist non-senescent for up to 4 weeks in F. superba (C.K. Yeo, pers.…”

“…Many have focused on immediate meteorological explanations (e.g., Milton et al 1982;Bronstein 1989;Milton 1991;Bronstein and Patel 1992;Smith and Bronstein 1996;Zhang et al 2006;Pereira et al 2007), while few also studied supraannual events (e.g., Bronstein and Hossaert-McKey 1995;Harrison 2000). But they do not examine how meteorology could affect the phenology through pollinator-plant interaction, even though other studies have shown that the duration of receptivity could be extended in the absence of pollinators (Bronstein 1988;Khadari et al 1995;Ansett et al 1996a). Yang et al (2000Yang et al ( , 2005 have reported seasonal variation in pollinator foundress number, seed yield, pollinator progeny yield, and empty galls in Xishuangbanna, Yunnan, China.…”

Larger Fig Wasps Are More Careful About Which Figs to Enter – With Good Reason

“…hispida is typical for Ficus species [20,21,36]. It increases the probability that un-pollinated figs will overlap with the arrival of pollinators released from figs on other trees, but is achieved at the cost of reduced productivity among older figs on both male and female trees.…”

“…Figs start to become less attractive to other pollinators a few hours after they have been entered, though this is postponed in some species if they have only received a single pollinator [20,21]. The cessation of release of attractant volatiles may reflect both the termination of production and closure of the ostiole.…”

“…Floral longevity (the length of time that a flower remains available for pollination) varies greatly among different plant species, and reflects a balance between the benefits of greater likelihood of pollinator visitation and the cost of flower maintenance [22–25]. Figs display extended floral longevity and if they are not entered by fig wasps they remain attractive to pollinators for days or weeks [20,21,26], but prolongation of receptivity may come at the cost of reduced reproductive efficiency among older figs [20]. Two studies have reported that pollinator females are more likely to enter younger figs [21,26], though the proximal causes of this preference have not been established.…”