Review of the inquilinous fauna associated with insect galls in Brazilian restingas

Several records of associated fauna, including parasitoids, inquilines, predators, and successors, have been reported by insect gall inventories in Brazilian restingas. Although most guilds are well established, inquilines have frequently been misinterpreted. In this paper, the inquilinous fauna of insect galls is revised based on five criteria: food habit; coexistence with the inducer; modification of gall tissues or production of new tissues; phylogenetic relationship with the inducer; and mobility. Gall inventories dated from 1988 to 2019 were examined, totaling 16 publications, eight of them with inquiline records. This guild was reported in 53 gall morphotypes in 44 plant species and four morphospecies distributed among 36 genera of 24 host families for a total of 65 records. Most inquilines were repositioned into the cecidophage guild and others into the kleptoparasite guild, resulting in a large reduction in the frequency of inquilines (from 65 to five records), and in first reports of cecidophages and kleptoparasites, with 46 and 13 records, respectively. Cecidophage was the most diverse guild with insects of five orders (Diptera, Coleoptera, Lepidoptera, Hemiptera, and Thysanoptera) while kleptoparasites were represented only by two orders (Diptera and Hymenoptera) and inquiline solely by Hymenoptera. Other results indicate that Leptothorax sp. (Formicidae) could be a successor and not an inquiline.

Recent Progress Regarding the Molecular Aspects of Insect Gall Formation

Galls are characteristic plant structures formed by cell size enlargement and/or cell proliferation induced by parasitic or pathogenic organisms. Insects are a major inducer of galls, and insect galls can occur on plant leaves, stems, floral buds, flowers, fruits, or roots. Many of these exhibit unique shapes, providing shelter and nutrients to insects. To form unique gall structures, gall-inducing insects are believed to secrete certain effector molecules and hijack host developmental programs. However, the molecular mechanisms of insect gall induction and development remain largely unknown due to the difficulties associated with the study of non-model plants in the wild. Recent advances in next-generation sequencing have allowed us to determine the biological processes in non-model organisms, including gall-inducing insects and their host plants. In this review, we first summarize the adaptive significance of galls for insects and plants. Thereafter, we summarize recent progress regarding the molecular aspects of insect gall formation.

Recent Progress Regarding the Evolution and Molecular Aspect of Insect Gall Formation

Galls are characteristic plant structures formed by hypertrophy (excessive increase in cell size) and/or hyperplasia (cell proliferation) induced by parasitic or pathogenic organisms. Insects are a major inducer of galls, and insect galls can occur on plant leaves, stems, floral buds, flowers, fruits, or roots. Many of these exhibit unique shapes, providing shelter and nutrients to the insects. To form unique gall structures, all-inducing insects are believed to secrete certain effector molecules and hijack host developmental programs. However, the molecular mechanisms of insect gall induction and development is still largely unknown because of the difficulty of studying non-model plants in the wild. Recent progress in next-generation sequencing has allowed us to determine the structure of biological processes in non-model organisms, including gall-inducing insects and their host plants. In this review, we first summarize the evolutionary aspects of gall-inducing life histories and their adaptive significance for insects and plants. Then, we briefly summarize recent progress regarding the molecular aspects of insect gall formation.

Diversity of insect galls from Mato Grosso State, Brazil: Cerrado

The Midwest region of Brazil possesses large areas dominated by the Cerrado that is poorly known concerning insect gall and their interactions. In this study, we inventory the gall morphology, host plants, and the gall makers from Parque Nacional da Chapada dos Guimarães, Mato Grosso State, in areas of natural vegetation from Cerrado, for the first time. Samplings occurred in two expeditions, July 2012 and January 2013. We characterized 295 morphotypes of insect galls in 140 host plant species, with 89 gall makers; the richest family in host plants was Fabaceae (16.7%), and the species was Protium heptaphyllum (Aubl.) Marchand (Burseraceae, 3.7%). Parque Nacional da Chapada dos Guimarães is the richest Brazilian cerrado area in gall morphotypes (295) and the second in average morphotypes/host plant species (2.1). Additionally, six genera and 38 species are new records as host plants; two of them, Bernardia similis Pax and K.Hoffm and Ormosia macrophylla Benth., are new occurrences for Mato Grosso State, and other two, Vochysia petraea Warm. and Talisia subalbens (Mart.) Radlk. are listed in the Red List of Threatened Species IUCN. This inventory data represents a testimony of insect-plant interactions in a Brazilian Cerrado area that was consumed by an unprecedented fire in the dry season of 2020.

Diversity of insect galls from Mato Grosso State, Brazil: North Pantanal

The Pantanal Biome occupies 20% of the Brazilian territory extending its distribution over two Brazilian States, Mato Grosso and Mato Grosso do Sul. This Biome is one of Brazil's poorly known regions concerning insect gall and their interactions with host plants. In this study, we characterized for the first time the gall morphology, identified host plants and the gall makers from an area of Brazilian wetlands from Mato Grosso State, known as Pantanal Matogrossense. We sampled Pantanal Biome areas in Poconé municipality, along the Transpantaneira Road, Mato Grosso State, Brazil, in two expeditions, July 2012 and January 2013, with a total effort of 2 hours. We characterized 91 morphotypes of insect galls in 54 host plant species; 28 gall makers in 24 host plant species; the richest host plant families are Fabaceae, Myrtaceae, and Sapindaceae. Psidium guineense Sw. is the super host species. This area in Pantanal Matogrossense is the second in the richness of gall morphotypes (N=91) and average morphotypes/plant species (1.7), comparing phytophysiognomies. Additionally, 15 plant species are new record as host in galler-host plant interaction in the world. This number represents 30% of the total of host plant species sampled in Poconé. This inventory is new knowledge to the Pantanal Matogrossense and representing a unique testimony of insect-plant interactions consumed by the unprecedented fire that occurred in Pantanal Biome in the dry season of 2020.

Insights into Super-host Plant Species of Galling Insects in the Neotropical Region

Background: The term ‘super host’ plant is often used in the literature surrounding plant-galling interactions, but the different contexts in which the term is used generates doubt and confusion due to the absence of a systematic definition of the term’s meaning. Objective: In this study, we used 60 well-defined plant-galling assemblages to propose a systematic definition of super-host plants at the local and regional level. In addition, we investigated factors that explain the number of galling species per host plant at different geographic scales. Methods: Plant-galling assemblages were compiled from an extensive literature review on insect gall inventories carried out in Brazil. Results: We found 888 host plant species belonging to 94 families and 340 genera hosting 2,376 insect gall morphotypes. At a local scale, 33.2% of host plant species harbored one insect gall morphotype and 12.2% hosted two gall morphotypes, making up 45.4% of the host plant species in each locality. At the regional scale, 51.5% of host plant species harbored one insect gall morphotype, and 17.9% of host plant species hosted two gall morphotypes, corresponding to 69.4% of all host plant species. Based on the average number of galling species per plant species, we classified the plant species into: 1) Host species; 2) Multi-host species and 3) Super-host species. The super-host plant species that showed the greatest richness of gall morphotypes at the local level were Baccharis reticularia and Adenocalymma neoflavidu. Furthermore, we found a positive relationship between plant life-form architectural complexity and the number of galling species at the local level. At the regional scale, we registered five super-host species (Guapira opposita, Protium heptaphyllum, Copaifera langsdorffii, Myrcia splendens, and Byrsonima sericea) which hosted 21 or more insect gall morphotypes. The number of galling species per host plant species at the regional scale was influenced positively by geographic distribution rank and number of biomes in which each species of the plant occurs. Conclusion: The present study stands out as the first of its kind to provide a systematic standardization for the super-host plants and to investigate factors influencing these species.

Galhas entomógenas em três fragmentos de Mata Atlântica no extremo Sul Catarinense, Brasil

Fifteen insect gall morphotypes were found on 11 plant species (8 families) in three fragments of the Dense Ombrophylous Lowland Forest, in the municipalities of Maracajá, Içara and Araranguá, Santa Catarina. Most of the galls occurred in leaves, followed by stems galls and a single gall morphotype in Leandra sp. (Melatomastaceae), occurred in both leaves and stems. Glabrous and isolated galls were more frequent than hairy and gregarious galls. Lauraceae was the family of plant with greater wealth of galls. It was pointed out the first record of the plant Microstachys serrulata (Euphorbiaceae) for the state of Santa Catarina. Galls found in Ilex theezans (Aquifoliaceae), Microstachys serrulata (Euphorbiaceae), Dahlstedtia muehlbergiana (Fabaceae), Nectandra oppositifolia (Lauraceae), Leandra sp. (Melastomataceae), Miconia sellowiana (Melastomataceae), Myrcia multiflora (Myrtaceae) and Urera nitida (Urticaceae) were recorded for the first time in the State of Santa Catarina.

Insect galls of the Reserva Biológica União, Rio de Janeiro, Brazil

Several inventories of insect galls have been performed in the Atlantic Forest of Rio de Janeiro, mostly in restingas, whereas the other phytophysiognomies remain poorly sampled. The present study inventoried the insect galls of Reserva Biológica União (RJ), a protected area comprising mainly Ombrophilous Forest. Field work was performed every two months from January to October, 2013. Insect galls were collected, photographed, characterized and transported to the laboratory. Adults were obtained by rearing and immature stages by gall dissection. The insects were deposited in the Cecidomyiidae Collection of the Museu Nacional. A total of 153 gall morphotypes were found on plants representing 37 plant families, 69 genera, 55 species and 53 morphospecies. Among them, two plant genera and five species were reported for the first time as host plants in Ombrophilous Forest. REBIO União showed little similarlity of host plant species and insect gall morphotypes when compared with other investigated Ombrophilous Forest areas. The leaf was the most attacked plant organ as expected. Asteraceae, Bignoniaceae, Fabaceae and Myrtaceae, and Mikania (Asteraceae) and Myrcia (Myrtaceae) were the richest host families and genera, respectivey, in number of gall morphotypes, all previously indicated as superhosts by other Brazilian Ombrophilous Forest inventories, except Bignoniaceae. Their great species richness may be related to their great gall richness, adding evidence in support of the taxon size hypothesis. Fusiform and globose galls were the most frequent, green was the predominant color, and most morphotypes did not present an indumentum. The highest gall richness was recorded in June and August. The gallers were distributed among Diptera (Cecidomyiidae), Lepidoptera, Hymenoptera, Hemiptera and Thysanoptera, with the first being predominant, following a global pattern. Eight gall-inducing species are recorded for the first time in REBIO União and four in Ombrophilous Forest. About 25% of the gall morphotypes were occupied by dwellers other than those that created the gall. They comprised parasitoids (Hymenoptera), inquilines (Diptera: Sciaridae and Muscomorpha, Hemiptera, and Lepidoptera) and successors (Psocoptera, mites, and Hymenoptera: Formicidae). Although these taxa were previously reported by Brazilian inventories of insect galls, 12 new association with plants are recorded. The amount of new records reinforces the importance of inventories.

Insect galls thrive on salt stressed big sagebrush host

The sagebrush steppe is estimated to occupy 4.4 percent of the total land area in the United States. In this ecosystem, the most common sagebrush species in most areas is big sagebrush, Artemisia tridentata. Big sagebrush provide a common host for galling insects. We observed that even in salt stressed environments big sagebrush grow and galling insects use them as hosts. In this study we test the hypothesis that there is a significant difference in insect gall density on salt stressed big sagebrush compared to unstressed big sagebrush. To test this, we collected data from four salt stressed sage plots and four unstressed plots at Columbia National Wildlife Refuge in Othello, Washington during 2010. We report significantly greater average gall density on plants in salt stressed plots. We collected four types of galls (artichoke, white fuzzy, black fuzzy, smooth, and other) and observed no significant difference in the diversity of galls on sage in salt stressed plots compared to the control. Further studies are needed to understand why salt stressed sage show greater density of galls, why insect galls seem to thrive on salt stressed sage.