Every end is a new beginning: Histological features of galls induced on Macairea radula (Melastomataceae) allow a post-senescence colonization

Abstract

Galls are a kind of plant-organism interaction defined as a manifestation of the reprogramming of plant cell growth induced by organisms with ecological impacts on host plants. The galling insect taxa and the targeted plant organ for oviposition determine the gall morphology and its histological features. Galls induced at budding sites can develop morphologically more complex structures due to the greater meristematic potential of their tissues. In addition, as buds can develop into shoots, bud galls should have a modified stem-like structure, which may remain attached to the plant for long periods after the galling insects emerge. Herein, we conducted histological analyzes in galls induced by Palaeomystella oligophaga on Macairea radula to investigate (i) if the galls induced on buds develop as stem-branches-like connections, with histological characteristics that favor their affixation to the host plants after senescence. Also, we inspected senescent galls to investigate (ii) if the microhabitats within these galls are occupied by opportunistic arthropods. The structural features of M. radula galls allowed us to diagnose them as stem-like galls, which develop as stems with shortened internodes with leaf-like projections. The stem-branch vascular connection allows these galls to remain fixed on the host plants for long periods and work as shelters for different taxa of arthropods in all sampled ecosystems. The interactions here go beyond the impacts on both galling insect and host plant populations, with trophic and non-trophic interactions allowing us to understand the insect P. oligophaga as a shelter-builder and an ecosystem engineer.