Koinobiont community structures among concealed herbivores on the same plant species

Parasitoids are a megadiverse group, and some of the most speciose parasitoid communities are associated with leaf miners. For koinobiont endoparasitoids, host discrimination is important, but parasitoids can hardly contact host individuals before laying eggs. However, we know little about the extent to which parasitoids specialize in different leafminer species coexisting on the same host plant. This study compared the community structures of ichneumonoid koinobiont endoparasitoids among leaf miners of Gracillariidae (Lepidoptera) on three fabaceous plant species, Pueraria lobata, Lespedeza bicolor and Wisteria floribunda, in Japan. Each of the three fabaceous species is utilized by three to four non-congeneric gracillariid species. We collected 11 parasitoid species from nine gracillariid leafminer species belonging to six genera. None of the collected parasitoid species emerged from all the gracillariid species that shared a host-plant species, nor from all the congeneric gracillariid species on different host-plant species. Although significant community structures were not detected, the “parasitoid–host genus” network exhibited higher network-level specialization (H2′ = 0.7701) than the “parasitoid–plant species” network (H2′ = 0.6511). Cryptic divergence (>5%) was also detected among individuals in Centistidea mogrus (Papp) (Hymenoptera: Braconidae), which were divided into two monophyletic clades; one showed wider association with gracillariids and plants, whereas the other specialized on a single gracillariid taxon on a specific host plant. Our results indicate that the majority of koinobiont endoparasitoids utilizing gracillariid leaf miners exhibit species-specific interactions with their host, even when multiple gracillariid species are associated with the same host plant species.