Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

Galls, abnormal plant tissues induced by insect oviposition and feeding, exhibit a wide range of morphological diversity. It has been traditionally believed that gall morphology is primarily determined by the species of gall-inducing insects, implying control from the insect side. However, comparative analysis of numerous gall morphologies has revealed a distinct pattern: galls induced on stems tend to display simpler structures, whereas those formed on leaves exhibit a high degree of morphological diversity, including both simple and complex forms. This observation suggests the presence of factors within the host plant, specifically in relation to the oviposition site, that influence gall morphology. Notably, leaves exhibit significant morphological diversity, whereas stems primarily serve as structural supports with minimal morphological variation. Therefore, we propose a hypothesis that factors such as cell size, secondary metabolites, and physical strength within organ tissues contribute to the constraints on gall formation. This study aims to quantitatively investigate the morphological diversity of plant galls using a large-scale open dataset comprising citizen-contributed biological observations. Utilizing mathematical analysis of a substantial number of gall images, we will examine whether the complexity of gall morphology correlates with the characteristics of the inducing organ across diverse plant species. Furthermore, by conducting quantitative assessments of three-dimensional structures and mechanical properties of sampled galls, we aim to identify the biological and physical factors that govern the morphological diversity observed in galls.