Substrate–Host–Parasitoid Networks in Decomposing Organic Resources in Brazil: Ecological Specialization, Community Connectivity, and Resource-Mediated Associations

Diptera developing in decomposing organic resources interact with diverse hymenopteran parasitoids, but these associations are often analyzed separately according to host, substrate, parasitoid species, or parasitism rate. This study integrated eight experimental datasets from Brazil to reconstruct the ecological network connecting decomposing substrates, dipteran hosts, and Hymenoptera parasitoids. Only experimentally demonstrated host–parasitoid associations were retained, principally those based on parasitoid emergence from identified dipteran pupae or puparia. Passive captures obtained exclusively with Malaise or yellow pan traps were not converted into trophic links. The consolidated evidence was organized as substrate → Diptera host → Hymenoptera parasitoid interactions, with special treatment of duplicated records and gregarious parasitoids. The reconstructed network showed pronounced heterogeneity among substrates, hosts, and parasitoids. High host abundance did not consistently correspond to high proportional parasitism, indicating that host availability alone was insufficient to explain interaction strength. Chi-square analyses supported significant differences in host distribution, parasitoid abundance, parasitism, substrate use, and host–parasitoid associations across several experimental systems. A limited group of parasitoids formed recurrent links among multiple hosts and resources, whereas other interactions remained comparatively restricted. Pachycrepoideus vindemmiae (Rondani, 1875) (Hymenoptera: Pteromalidae) represented an important cross-resource connector, occurring in fecal, carrion-associated, animal-tissue, fish, fruit, and manure systems. Temporal variation in decomposing substrates, particularly bovine feces, further altered host availability and parasitoid occurrence. Overall, decomposing organic resources functioned as ecological filters that structured trophic connectivity by determining which dipteran hosts became available to parasitoids. The resulting network framework provides an integrative basis for interpreting parasitoid specialization, biological control, livestock and agricultural systems, medical-veterinary entomology, and forensic ecology in Brazil.