Structural, histochemical, and ecological peculiarities of lenticular leaf galls induced on the epiphytic fern Microgramma vacciniifolia (Polypodiaceae)

Abstract

Interactions among gall inducers and ferns, particularly in epiphytic Polypodiaceae, remain poorly understood. In this study, we investigated lenticular Cecidomyiidae galls induced on the leaves of the epiphyte Microgramma vacciniifolia and compared their developmental cycle, interactions, and anatomical, histochemical, and histometrical profiles with those of ungalled leaves. These galls, covered by a silky film produced by the larva, exhibit a multivoltine life cycle, with induction occurring on expanded leaves throughout both dry and rainy seasons. Interactions with Holopothrips (Thysanoptera) were observed during the rainy season, suggesting potential predation and kleptoparasitism. Anatomical and histometric changes in galls are minimal, but the cell layer in contact with the gall inducer strongly accumulates reducing sugars, proteins, lipids, and phenolics, likely supporting larval nutrition and the plant’s antioxidant response. Comparing these galls to those on other epiphytic Polypodiaceae, such as Niphidium crassifolium, and investigating the phylogeny of the galling Cecidomyiidae could reveal whether these relationships coevolved and whether gall simplicity represents an ancestral trait or a derived adaptation in ferns. This study highlights the need for further research to understand the evolutionary and ecological dynamics of plant–insect interactions in epiphytic systems.