No abstract

Galling herbivores induce structural and chemical alterations in their host plant's tissues. These insects have been the focus of little study in the case of Australian taxa. Leptocybe invasa, a native Australian galling hymenopteran associated with Eucalyptus species, causes economic damage to plantation eucalypts in many countries around the world. Leptocybe invasa oviposits in the midribs and petioles of expanding leaves thereby intercepting photosynthates and impairing normal expansion. We analysed the ultrastructural and chemical cellular changes in L. invasa galls on Eucalyptus camaldulensis (probably subspecies camaldulensis) to diagnose how the insect manipulates plant cells and tissues and the significance of these alterations for insect nutrition and protection. Galling stimuli induce the formation of two functionally compartmentalised types of tissue. Phenolic plant secondary metabolites and anthocyanins (plant pigments) accumulate in the outer compartment, while primary metabolites accumulate in the inner compartment. The nutritive cells (inner compartment) accumulate protein and lipids that provide food for the larvae. Total polyphenol concentrations did not differ significantly between outer and inner compartments. Nevertheless, the concentrations of quercetin and kaempferol derivatives were higher in the outer compartment than in the inner compartment. These differences could be related to the protection of plant tissues against ultraviolet rays and the maintenance of redox homeostasis. There were higher ratios of hexahydroxydiphenoyl‐containing hydrolysable tannins rather than galloyl‐containing hydrolysable tannins in the inner compartment. This shift in the oxidative capacity of the polyphenols in the inner compartment could represent a defensive plant response to the larvae.

Thysanoptera-induced galls commonly culminate in simple folding or rolling leaf gall morphotypes. Most of these galls are induced by members of the suborder Tubulifera, with only a few species of the suborder Terebrantia being reported as gall inducers. The Terebrantia, as most of the gall inducers, manipulates the host plant cellular communication system, and induces anatomical and biochemical changes in its host plant. In an effort to keep its homeostasis, the host plant reacts to the stimuli of the galling insect and triggers chemical signaling processes. In contrast to free-living herbivores, the signaling processes involving galling herbivores and their host plants are practically unknown. Current investigation was performed into two steps: first, we set the structural profile of non-galled and galled leaves, and looked forward to find potential alterations due to gall induction by an undescribed species of Nexothrips (suborder Terebrantia) on Myrcia splendens. Once oil glands had been altered in size and number, the second step was the investigation of the chemical profile of three tissue samples: (1) non-galled leaves of a control individual, (2) non-galled leaves of galled plants, and (3) galls. This third sample was divided into two groups: (3.1) galls from which the inducing thrips were manually removed and (3.2) galls macerated with the inducing thrips inside. The chemical profile was performed by gas chromatography/ mass spectrometric detector after headspace solid-phase extraction. The galling activity of the Nexothrips sp. on M. splendens culminates in mesophyll compactness interspersed to diminutive hypersensitive spots, development of air cavities, and the increase in size and number of the secretory glands. Seventy-two compounds were completely identified in the volatile profile of the three samples, from which, sesquiterpenes and aldehydes, pertaining to the “green leaf volatile” (GLVs) class, are the most abundant. The rare event of gall induction by a Terebrantia revealed discrete alterations toward leaf rolling, and indicated quantitative differences related to the plant bioactivity manipulated by the galling thrips. Also, the content of methyl salicylate has varied and has been considered a potential biomarker of plant resistance stimulated as a long-distance effect on M. splendens individuals.

No abstract

Urban environments are critical points for biological invasions because these areas are susceptible to a greater number of environmental disturbances. Because they are densely populated ecosystems, urban environments present a unique opportunity for the involvement of society in the management of invasive exotic species. Similarly, citizen science offers opportunities to conduct research in the field of ecology together with society. The objective of our study was to analyze the occurrence of exotic species in urban areas recorded on iNaturalist and determine whether citizen science applications are good data sources for research projects in invasion ecology. Specifically, we evaluated whether richness and composition of the exotic species community in the cities registered on the iNaturalist platform were explained by socioeconomic and environmental factors. We also verified whether richness of the exotic species in cities registered on the iNaturalist platform were similar to the richness of the exotic species community in the region where the city is located using data collected only by researchers. We obtained 38,374 occurrences of 265 invasive species covering 2,057 cities in 72 countries. Occurrence records were concentrated in North America, Western Europe and Oceania, and there were no data for cities in most of Africa, the Middle East, Eastern Europe and West Asia. Socioeconomic and environmental factors were important determinants of the richness of exotic species in urban areas of the world and were important determinants of the richness of exotic species in natural environments. Urban hotspots of invasive exotic species were different from those for ecosystems in general.