Insects feeding on seeds and fruits at BCI, KHC and WAN

Unlike mutualistic pollination and seed dispersal networks, antagonistic seed
predation networks have not been well studied in the tropics. We tested
whether the structure of antagonistic tripartite networks composed of host
plants, insects breeding in seeds and fruits and their insect parasitoids at
three representative rainforest locations (Panama, Thailand, Papua New Guinea)
can be predicted from plant phylogeny and plant traits. We considered subsets
of the networks at each location, either based on insect families, plant
families or plant functional groups. We reported 3,197 interactions and
observed a low percentage of realized interactions, especially at the
Panamanian site, where insect host specificity was higher than at the other
two sites. Seed-eaters were more host-specific than pulp-eaters and insects
feeding on dry fruits were more host specific than those feeding on fleshy
fruits. Local plant richness did not influence insect host specificity, but
other site characteristics may be important in this regard. Most networks were
extremely specialized, such as those including Tortricidae and Bruchinae at
the Panamanian site. Apart from sampling effort, plant phylogeny had an
important effect on network structure, but this effect was not overwhelming,
as variables related to plant resource (basal area) or plant traits (number of
seeds per fruit) were also important, particularly for networks based on plant
functional groups. Path analyses revealed no direct correlation between the
number of compartments in plant-herbivore networks and those in plant-
parasitoid networks, indicating limited support for the nasty host hypothesis.
Our study emphasizes the duality between seed dispersal and seed predation
networks in the tropics, as the former are not very specific while the latter
are far more specialized and may include different keystone plant species.
This underlines the need to study both types of networks including a variety
of potential keystone plant species for sound practices of forest
regeneration.