From chambers to communities: gall architecture shapes parasitoid network stability in Diplolepis (Cynipidae, Diplolepididae) rose galls

Abstract

1. Gall-inducing insects create structurally distinct microhabitats that mediate their interactions with associated parasitoid communities, and variation in gall architecture is recognized as an important driver of the composition and organization of these communities. 2. In cynipid gall wasps of the genus Diplolepis, galls range from single-chambered to multichambered structures, and this variation has previously been linked to differences in parasitoid attack rates and community composition, yet its consequences for the topology and stability of the resulting ecological networks remain unexplored. 3. We compiled 17 empirical Diplolepis-parasitoid interaction networks spanning seven host taxa and used dynamical (non-normalized return time) and structural (robustness) measures of stability, together with network topology and diversity metrics, to test whether gall architecture shapes the organization of the resulting parasitoid networks. We hypothesized that networks associated with multichambered galls would be more stable, more connected and more unevenly structured than those associated with single-chambered galls. 4. Multichambered-gall networks showed significantly higher robustness at the species level and lower species-level non-normalized return times under intermediate and weak self-regulation, together with higher species-level connectance and clustering coefficients. In contrast, gall architecture reduced rather than increased Shannon diversity after accounting for network size, and had no detectable effect on the Gini index. Most effects weakened after aggregation to the genus level, highlighting the sensitivity of gall-associated network descriptors to taxonomic resolution. 5. These results indicate that gall architecture leaves a measurable signature on the organization and stability of associated parasitoid networks that extends beyond simple differences in community composition, adding a network-level perspective to the study of gall morphology as an ecological filter of natural-enemy communities.