In the fig (Moraceae) and fig-wasp (Agaonidae) mutualism, scent is believed to be of primary importance in pollinator attraction and maintenance of species specificity. Scent divergence between closely related Ficus species seems sufficient in promoting reproductive isolation through pollinator behaviour, starting the process of speciation. We investigated volatile organic compound (VOC) variation from figs in several Ficus species endemic to Papua New Guinea. Sister species of section Papuacyse and subspecies of Ficus trichocerasa substitute each other along the continuously forested Mt. Wilhelm elevational gradient. We placed these species in a phylogenetic context to draw conclusions of scent divergence between close relatives. In addition, pollinator response to VOCs emitted by figs of different species was tested. Volatile profiles differed significantly between focal species, although with a varying degree of overlap between (sub)species and elevations. Pollinators were generally attracted to VOCs emitted only by their hosts except in one case where pollinating fig wasps were also attracted to the sister species of its host. Wasp morphological traits, however, indicate that it is mechanically impossible for this species to oviposit in figs of this atypical encounter. Synthesis. This study demonstrates that while scent is an effective signal for partner recognition, there are multiple barriers which help maintain prepollination isolation in fig and pollinating fig-wasp interactions. Speciation along this elevational gradient is reinforced by divergence in key reproductive isolation mechanisms on both sides of the mutualism.
|Original language||English (US)|
|Number of pages||18|
|Journal||Journal of Ecology|
|State||Published - Nov 2018|
Bibliographical noteFunding Information:
We thank our assistants from the villages of Ohu, Numba, Bundi Station, Degenumbu and Sinopass and the staff of the New Guinea Binatang Research Centre in Papua New Guinea. We thank the Papua New Guinea Forest Research Institute and the Department of Environment and Conservation for help in granting plant and wasp export permits. We also thank the staff of the PACE platform of the labex CeMEB (“Centre Méditerranéen de l’Environment et de la Biodiversité”) and two anonymous reviewers for help in improving the manuscript. Access to computing and storage facilities was provided by the National Grid Infrastructure MetaCentrum provided under the programme “Projects of Large Research, Development and Innovations Infrastructures” (CESNET LM2015042). S.T.S. acknowledges funding from the Grant Agency of the Czech Republic (grant number 15-24571S). D.S.V. was, in part, supported by GA JU grant (152/2016/P) provided by the University of South Bohemia. V.N. acknowledges funding from the Darwin Initiative for the Survival of Species (22-002).
© 2018 The Authors. Journal of Ecology © 2018 British Ecological Society
- character divergence
- evolutionary ecology
- fig pollination
- fig-wasp attraction
- reproductive isolation
- sister species
- volatile organic compounds (VOCs)