Résumé
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.