Data from: Strength of enemy release from parasitoids is context-dependent in the invasive African Fig Fly, Zaprionus indianus

Understanding the mechanisms underlying the success of biological
invasions is essential to employ effective prediction and management
strategies. The escape from natural enemies in invaded regions (enemy
release hypothesis) and increased competitive ability are hallmarks of
invasive species; however, these two processes are rarely studied within
the same context. Here, we examined the effect of enemy release on the
competition outcomes of a successful invasive insect pest in North
America, the African fig fly (Zaprionus indianus). Parasitoid wasps such
as Leptopilina heterotoma that parasitize drosophilid larvae may seek out
established species with known host suitability over a novel species, so
we hypothesized Z. indianus may have low susceptibility to parasitoids,
giving them a competitive advantage over co-occurring drosophilids. We
tested this hypothesis by comparing the adult emergence rates from Z.
indianus larvae reared alone or in competition with Drosophila hydei or D.
simulans larvae in the presence and absence of parasitoid wasps. These
interactions might be influenced by larval density, so we tested
competitive interactions under low and high larval densities. At low
larval densities, Z. indianus emerged at equal rates to D. hydei but
outcompeted D. simulans, and these outcomes were not affected by
parasitoids. However, at high densities, the addition of parasitoids
shifted competition outcomes in favor of Z. indianus, suggesting enemy
release provides a competitive advantage under some circumstances. These
results indicate that the strength of enemy release in Z. indianus is
widely dependent on contextual factors such as density and competitor
species. Further investigation of how these results apply to field
environments could offer insight into how Z. indianus alters ecosystems
and how productive biological control may limit the spread of Z.
indianus.