Data from:Parasites and investment to host inflorescences in a fig tree-fig wasp mutualism

Most mutualisms are parasitized by third-party species that inflict costs
on the mutualists. How such parasites affect mechanisms that help maintain
mutualism stability is poorly understood, even in well-studied systems.
Angiosperm plants tend to invest most resources in tissue that yields high
net benefits. In mutualisms with plant hosts, a reduction in such
investment can function as a key stability-promoting mechanism, such as in
fig-wasp mutualisms. Here, uncooperative symbiont wasps that fail to
pollinate incur ‘sanctions’ via reduced host investment to unpollinated
figs, realized via fig abortion, killing all wasp offspring, or via
elevated offspring mortality within unaborted figs. We experimentally
exposed host Ficus racemosa figs to parasitic wasps Sycophaga fusca, which
convert fig flowers into offspring without benefitting host trees, with or
without uncooperative (pollen-free) or cooperative (pollen-laden) symbiont
pollinator wasps Ceratosolen fusciceps. Pollen-free C. fusciceps were
still able to convert fig flower ovaries into wasp offspring, whereas
those naturally pollen-laden were prevented from reproducing by
experimental manipulation. Independent of the effects of pollination and
reproduction by pollinators, increased exposure to S. fusca parasites
resulted in reduced rates of fig abortion and gall failure in unaborted
figs. Although S. fusca converts flower ovaries that could otherwise
become beneficial pollinator offspring or fig seeds into parasite
offspring, figs with intermediate levels of parasite exposure received
high levels of investment. Our results suggest that S. fusca parasite
oviposition/larval activities can result in host trees boosting investment
in figs, even when this may counter the tree’s interests. We suggest that
oviposition/larval activity by these parasites may mimic the biochemical
pathways of pollinator gall formation and seed production.