Urbanization Intensity, Vegetation Cover and Plant Vigor Affects Stem Galls Occurrence and Abundance in a Widely Distributed Ruderal Tropical Plant

ABSTRACT Urbanization is a major driver of environmental change and biodiversity loss, impacting species and ecological interactions. Insects, as key terrestrial biodiversity components, engage in diverse interactions with plants, including gall induction. Host plant vigor often predicts higher herbivore abundance, but this relationship is understudied in urban contexts. We investigated the effects of urbanization intensity, vegetation cover, and plant vigor on the occurrence and abundance of stem galls in Turnera subulata , a widespread tropical ruderal species. Surveys were conducted at 14 sites across an urbanization gradient in Penedo, Brazil. For each plant, we recorded stem gall presence and abundance and measured vigor through biomass‐related traits. Impervious surface area was used as a proxy for urbanization intensity, and native vegetation cover as an indicator of native vegetation. Results showed that urbanization did not influence gall occurrence but reduced gall abundance. Conversely, sites with greater vegetation cover had higher gall occurrence and abundance. Additionally, more vigorous plants, particularly those with greater stem biomass, hosted more galls, supporting the plant vigor hypothesis. These findings underscore the role of vegetation cover in maintaining specialized interactions between gall‐inducing insects and host plants, mitigating urbanization's negative effects on these herbivores. Our study provides evidence that plant vigor remains a key factor influencing gall abundance in urban environments. We advocate for the conservation and strategic planning of native vegetation in tropical cities to sustain specialized ecological interactions amid ongoing urban expansion.