Floral scent divergence and pollinator morphology promote pollinator isolation and potential speciation in the fig and fig-wasp mutualism
The article in Journal of Ecology that while scent is an effective signal for partner recognition, there are other barriers which help maintain the stability of such a species specific mutualism.
In the fig and fig-wasp mutualism, scent is believed to be of primary importance in the attraction of pollinators and maintenance of species specificity. Divergent scent signals between closely related species should be sufficient in promoting reproductive isolation starting the process of speciation. In this study we analyzed the scent signals of four fig species endemic to Papua New Guinea. Using next generation sequencing, we placed these species in a phylogenetic context to draw conclusions of scent divergence between close relatives. In addition to this, using standard Y-tube choice experiments on pollinating wasps, we tested pollinator response to the scent emitted by different fig species. Scent profiles varied significantly between all focal species, although with a varying degree of overlap between them. Pollinators were generally attracted to the scent emitted by its host species except in one case where the pollinating fig-wasp of one species was also attracted to the sister species of its host fig. Wasp morphological traits, however, indicate that it is mechanically impossible for her to oviposit inside figs of this atypical encounter. This study demonstrates that while scent is an effective signal for partner recognition, there are other barriers which help maintain the stability of such a species specific mutualism. Speciation appears to be reinforced by divergence in key reproductive isolation mechanisms on both sides of the mutualism.
Souto-Vilarós D., Proffit M., Buatois B., Rindoš M., Sisol M., Kuyaiva T., Isua B., Michálek J., Darwell C., Hossaert-McKey M., Weiblen G., Novotný V., Segar S. T. (2018) Pollination along an elevational gradient mediated both by floral scent and pollinator compatibility in the fig and fif-wasp mutualism. Journal of Ecology (in press). https://doi.org/10.1111/1365-2745.12995