Evidence for intersexual chemical mimicry in a dioecious plant

Abstract

The dioecious Mediterranean fig, Ficus carica, displays a unique phenology in which males sometimes bloom synchronously with females (in summer), and sometimes not (in spring). Ficus carica is engaged in an obligatory mutualism with a specific pollinating wasp, which reproduces only within figs, localising them by their specific scents. We show that scents emitted by male figs show seasonal variation within individual trees. Scents of summer male figs resemble those of the co-flowering females, and are different from those of the same male trees in spring, when female figs are absent. These differences hold even if only compounds electrophysiologically active for pollinators are considered. The similar scents of summer males and females may explain why the rewardless females are still pollinated. These results offer a tractable model for future studies of intersexual chemical mimicry in mutualistic pollination interactions.

Active pollination favours sexual dimorphism in floral scent

“…Floral scents of male and female flowers are usually similar, if not identical, in animal-pollinated plants, reflecting their need to attract the same animal to flowers of both sexes [8]. Contrary to this prevailing pattern, our results demonstrate a remarkable difference in floral scent between sexes of animal-pollinated plants.…”

“…This is because plants must attract the same animal to both male and female flowers to secure conspecific pollen transfer [7], and thus are selected to produce similar floral signals in the flowers of both sexes. Selection for male and female flowers to resemble each other is particularly strong when one sex (often the female) produces little or no reward and effectively mimics flowers of the other sex [5,8].…”

How to be an ant on figs

“…Fig volatile signals change with syconia development and these changes are used by pollinating fig wasps and NPFWs to locate syconia at the correct phase of development for oviposition (Proffit et al, 2007(Proffit et al, , 2009Ranganathan et al, 2010;Soler et al, 2012). This variation in odors emitted by figs can also potentially be used by ants to synchronize and enhance their predatory activity.…”

Female figs as traps: Their impact on the dynamics of an experimental fig tree-pollinator-parasitoid community

“…However, this selection pressure also favours female plants that mimic males, as has been described in many other plant species (Agrenet al 1986;Aronne et al, 1993;Dufaÿ and Anstett, 2004). Furthermore, male plants also need to mimic females to ensure that the next generation of wasps bearing their pollen enter female figs ('vicarious selection', Grafen and Godfray, 1991;Soler et al, 2012). The inability of fig wasps to differentiate between male and female figs means that female fig plants act as a source of mortality among adult female pollinators, and some pollinator populations pass through repeated bottlenecks as a result (Kjellberg et al, 1987).…”

“…In some dioecious species, the short-lived adult females (that live only few hours) enter the female figs because during certain periods of the year they have no other choice available, as they are released when few receptive figs are present on male trees (Kjellberg et al, 1987;Soler et al, 2012). In others, such as Ficus montana, male and female figs are receptive simultaneously and selection should favour wasps that avoid female figs, leading eventually to the potential extinction of the plant and its pollinator (Patel et al, 1995;Corlett, 1987;Anstett et al, 1998;Suleman et al, 2011a).…”