Quantitative trophic networks of insect gallers and their parasitoids in the hybrid oak complex Quercus magnoliifolia x Quercus resinosa

Oak hybridization have important effects on the structure of herbivorous insect communities and associated natural enemies. We tested the effects of hybridization between Q. magnoliifolia and Q. resinosa on insect gallers trophic networks and their parasitoids. We characterized the genotypes of 35 individuals of Q. magnoliifolia, 30 of Q. resinosa, and 57 hybrids using eight nuclear microsatellite markers. We collected 6,798 galls from the oak hybrid complex distributed in 33 gall morphospecies on Q. magnoliifolia, 28 on Q. resinosa, and 42 on hybrid oaks. Galler-parasitoid networks were realized by 21 gall morphospecies and 21 parasitoid species for Q. magnoliifolia; 16 gall morphospecies and 30 parasitoid species for Q. resinosa; and 25 gall morphospecies and 23 parasitoid species for hybrids. Plant-galler networks were different among three oak groups, having the hybrid network higher values of diversity of interactions, nestedness and modularity and lower values of specialization than Q. magnoliifolia and Q. resinosa networks. Hybrid network of gallers and parasitoids had higher diversity of interactions, connectance and generality and lower modularity than Q. magnoliifolia and Q. resinosa networks. Hybrids are more vulnerable to insect galler incidence having low pressure by parasitoids, which allow more gall incidence in hybrid plants. Our study corroborated that hybridization generates changes in oak genetic composition influencing insect gallers trophic networks and their parasitoids. Our findings are also consistent with the rule of genetic similarity which suggest a relationship between plant genetics and the associated arthropod community, where genetically similar plants support similar arthropod communities.

Automated summary

Hybridization of oak trees has significant effects on the structure of herbivorous insect communities and their associated natural enemies. In this study, the effects of hybridization between Q. magnoliifolia and Q. resinosa on insect gallers and their parasitoids were examined. The results showed that the plant-galler networks and galler-parasitoid networks varied among different oak groups, with hybrid oak networks exhibiting higher diversity of interactions, connectivity, and generality. Hybrids were more susceptible to insect galler incidence and had lower pressure from parasitoids.