Phylogeny, evolution and classification of gall wasps: the plot thickens

Modelling suggests Wolbachia-induced cytoplasmic incompatibility in oak gall wasps with cyclical parthenogenesis

Oak gall wasps typically exhibit a life cycle with one sexual and one asexual generation each year. These wasps can carry various endosymbionts, one of which is the maternally inherited bacterium Wolbachia that can induce several reproductive manipulations on its host. Cytoplasmic incompatibility (CI) has been described as the most prominent of these manipulations. CI leads to embryonic mortality in the hosts' offspring when infected males mate with either uninfected females or with females that harbour different Wolbachia strains. It has been hypothesized that Wolbachia can induce CI in oak gall wasps. To address this hypothesis, we derived a mathematical model to investigate the spread of a bacterial infection in naive populations and to determine the plausibility of CI occurrence. To validate our model, we used published data from Wolbachia-infected Belonocnema kinseyi populations in two approaches. Our first approach uses measurements of infection frequencies and maternal transmission in the sexual generation. For the second approach, we extended the model to compare predictions to estimates of mtDNA-haplotypes, which, like Wolbachia, are maternally inherited, and can therefore be associated with the infection. Both approaches indicate that CI is present in these populations. Our model can be generalized to investigate the occurrence of CI not only for oak gall wasps but also for other species.

Cynipid wasps systematically reprogram host metabolism and restructure cell walls in developing galls

Many insects have evolved the ability to manipulate plant growth to generate extraordinary structures called galls, in which insect larva can develop while being sheltered and feeding on the plant. In particular, cynipid (Hymenoptera: Cynipidae) wasps have evolved to form morphologically complex galls and generate an astonishing array of gall shapes, colors, and sizes. However, the biochemical basis underlying these remarkable cellular and developmental transformations remains poorly understood. A key determinant in plant cellular development is cell wall deposition that dictates the physical form and physiological function of newly developing cells, tissues, and organs. However, it is unclear to what degree cell walls are restructured to initiate and support the formation of new gall tissue. Here, we characterize the molecular alterations underlying gall development using a combination of metabolomic, histological, and biochemical techniques to elucidate how valley oak (Quercus lobata) leaf cells are reprogrammed to form galls. Strikingly, gall development involves an exceptionally coordinated spatial deposition of lignin and xylan to form de novo gall vasculature. Our results highlight how cynipid wasps can radically change the metabolite profile and restructure the cell wall to enable the formation of galls, providing insights into the mechanism of gall induction and the extent to which plants can be entirely reprogrammed to form unique structures and organs.

Key to the North American tribes and genera of herb, rose, bramble, and inquiline gall wasps (Hymenoptera, Cynipoidea, Cynipidaesensu lato)

Robust keys exist for the family-level groups of Cynipoidea. However, for most regions of the world, keys to genera are not available. To address this gap as it applies to North America, a fully illustrated key is provided to facilitate identification of the tribes and genera of rose gall, herb gall, and inquiline gall wasps known from the region. For each taxon covered, a preliminary diagnosis and an updated overview of taxonomy, biology, distribution, and natural history are provided.

Discovery of a new species of Synergus (Hymenoptera, Cynipidae, Synergini) based on morphology and molecular data

A new species of gall inquiline, Synergusdilatatussp. nov., is described from Hubei Province, China. Morphological descriptions, photographs and biological information are provided. Mitochondrial cytochrome oxidase (COI) sequences of the new species were newly obtained and a molecular species delimitation analysis of 12 species of Synergus performed using the ASAP method recovered 16 molecular operational taxonomic units, providing support for recognition of the new species. The results also highlight a few conflicts between morphological and molecular species delimitations in Synergus.

Microbiome and plant cell transformation trigger insect gall induction in cassava

Several specialised insects can manipulate normal plant development to induce a highly organised structure known as a gall, which represents one of the most complex interactions between insects and plants. Thus far, the mechanism for insect-induced plant galls has remained elusive. To study the induction mechanism of insect galls, we selected the gall induced by Iatrophobia brasiliensis (Diptera: Cecidomyiidae) in cassava (Euphorbiaceae: Manihot esculenta Crantz) as our model. PCR-based molecular markers and deep metagenomic sequencing data were employed to analyse the gall microbiome and to test the hypothesis that gall cells are genetically transformed by insect vectored bacteria. A shotgun sequencing discrimination approach was implemented to selectively discriminate between foreign DNA and the reference host plant genome. Several known candidate insertion sequences were identified, the most significant being DNA sequences found in bacterial genes related to the transcription regulatory factor CadR, cadmium-transporting ATPase encoded by the cadA gene, nitrate transport permease protein (nrtB gene), and arsenical pump ATPase (arsA gene). In addition, a DNA fragment associated with ubiquitin-like gene E2 was identified as a potential accessory genetic element involved in gall induction mechanism. Furthermore, our results suggest that the increased quality and rapid development of gall tissue are mostly driven by microbiome enrichment and the acquisition of critical endophytes. An initial gall-like structure was experimentally obtained in M. esculenta cultured tissues through inoculation assays using a Rhodococcus bacterial strain that originated from the inducing insect, which we related to the gall induction process. We provide evidence that the modification of the endophytic microbiome and the genetic transformation of plant cells in M. esculenta are two essential requirements for insect-induced gall formation. Based on these findings and having observed the same potential DNA marker in galls from other plant species (ubiquitin-like gene E2), we speculate that bacterially mediated genetic transformation of plant cells may represent a more widespread gall induction mechanism found in nature.

Re-establishment of the Nearctic oak cynipid gall wasp genus Feron Kinsey, 1937 (Hymenoptera: Cynipidae: Cynipini), including the description of six new species

The Nearctic cynipid oak gall wasp genus Feron Kinsey, comb. rev., is re-established with 34 species: F. albicomus (Weld, 1952), comb. nov., F. amphorus (Weld, 1926), comb. nov., F. apiarium (Weld, 1944), comb. nov., F. atrimentum (Kinsey, 1922), comb. nov., F. bakkeri (Lyon, 1984), comb. nov., F. caepula (Weld, 1926), comb. nov., F. californicum (Beutenmueller, 1911), comb. nov., F. clarkei (Bassett, 1890), comb. nov., F. comatum (Weld, 1952), comb. nov., F. crystallinum (Bassett, 1900), comb. nov., F. cylindratum (Kinsey, 1937), comb. nov., F. discale (Weld, 1926), comb. nov., F. discularis (Weld, 1926), comb. nov., F. dumosae (Weld, 1957), comb. nov., F. gigas (Kinsey, 1922), comb. nov., F. izabellae Melika, Nicholls & Stone, sp. nov., F. kingi (Bassett, 1900), comb. nov., F. parmula (Bassett, 1900), comb. nov., F. pattersonae (Fullaway, 1911), comb. nov., F. roberti Melika, Nicholls & Stone, sp. nov., F. rucklei Melika, Nicholls & Stone, sp. nov., F. scutellum (Weld, 1930), comb. nov., F. serranoae Pujade-Villar & Cuesta-Porta, sp. nov., F. splendens (Weld, 1919), comb. nov., F. stellare (Weld, 1926), comb. nov., F. stellulum (Burnett, 1974), comb. nov., F. sulfureum (Weld, 1926), comb. nov., F. syndicorum Pujade-Villar & Cuesta-Porta, sp. nov., F. tecturnarum (Kinsey, 1920), comb. nov., F. tetyanae Melika, sp. nov., F. tibiale Kinsey, 1937, comb. rev., F. tubifaciens (Weld, 1926), comb. nov., F. verutum Kinsey, 1937, comb. rev., and F. vitreum Kinsey, 1937, comb. rev. Most species are known only from the asexual generation; F. clarkei, F. comatum, and F. dumosae are known only from the sexual generation, while both generations are recognised for F. atrimentum, F. crystallinum, F. gigas, F. kingi, and F. pattersonae. Matching of alternate sexual and asexual generations is established for the first time for F. kingi and F. pattersonae (= Andricus pedicellatus (Kinsey, 1922), syn. nov.) based on molecular data (both cytb and ITS2 sequences). Morphological descriptions, re-descriptions, diagnoses, and a key to species are given, as well as data on DNA sequences, biology, phenology, and distribution.

Revision of the Amphibolips niger group with the description of a new species (Hymenoptera: Cynipini)

Amphibolips is currently divided into two species-groups, clearly differentiated by adult and gall morphology. The niger group of Amphibolips species is revised. This complex includes eight species: A. gumia Kinsey, A. jubatus Kinsey, A. elatus Kinsey, A. maturus Kinsey, A. nebris Kinsey, A. niger Kinsey, A. pistrix Kinsey and A. ufo Cuesta-Porta & Pujade-Villar sp. nov. We provide descriptions of new species and re-descriptions of known species, diagnoses, keys to complexes and species. The possibility of the niger complex belonging to a new genus is also discussed.

The complete mitochondrial genome and gene rearrangements in a gall wasp species, Dryocosmus liui (Hymenoptera: Cynipoidea: Cynipidae)

Mitochondrial genomes (mitogenomes) have been widely used in comparative and evolutionary genomics, molecular evolution, phylogenetics, and population genetics, but very limited information is available for the family Cynipidae. In this report, we describe the mitogenome of Dryocosmus liui Pang, Su et Zhu, providing the first complete mitogenomic data for a cynipid gall wasp species. The mitogenome of D. liui is 16,819 bp in length, and contains the typical set of 37 genes. Two control regions were detected, with the second being a perfect inverted repeat of the major portion of the first. Gene rearrangements were found in transfer RNA (tRNA) genes, protein-coding genes (PCGs) and ribosomal RNA (rRNA) genes, compared with the putative ancestral mitogenome. Similar to two other Cynipidae species with mitogenome data available, D. liui has a novel tRNA gene cluster trnL1-trnI-trnL2-trnW-trnM-trnQ between nad1 and nad2. Phylogenetic analysis based on sequences of PCGs and rRNA genes with D. liui included obtained topologies identical to previous studies supporting the a relationship of (Cynipoidea , (Platygastroidea, Proctotrupoidea)) within the monophyletic Proctotrupomorpha and (Cynipidae, Figitidae), Ibaliidae) within the Cynipoidea.

Molecular Aspects of Gall Formation Induced by Mites and Insects

Recent publications on gall formation induced on the leaves of dicotyledonous flowering plants by eriophyoid mites (Eriophyoidea) and representatives of four insect orders (Diptera, Hemiptera, Hymenoptera, Lepidoptera) are analyzed. Cellular and molecular level data on the stimuli that induce and sustain the development of both mite and insect galls, the expression of host plant genes during gallogenesis, and the effects of these galling arthropods on photosynthesis are considered. A hypothesis is proposed for the relationship between the size of galls and the volume of secretions injected by a parasite. Multistep, varying patterns of plant gene expression and accompanying histo-morphological changes in the transformed gall tissues are apparent. The main obstacle to better elucidating the nature of the induction of gallogenesis is the impossibility of collecting a sufficient amount of saliva for analysis, which is especially important in the case of microscopic eriophyoids. The use of modern omics technologies at the organismal level has revealed a spectrum of genetic mechanisms of gall formation at the molecular level but has not yet answered the questions regarding the nature of gall-inducing agents and the features of events occurring in plant cells at the very beginning of gall growth.

Cynipidae (Hymenoptera, Cynipoidea) fauna of Burdur province (Türkiye)

Field studies were conducted between September 2020 and June 2022 to assess the gall wasp (Hymenoptera: Cynipidae) fauna of Burdur province (Southwestern Türkiye). A total of 69 species in 18 genera were recorded. Gall samples were collected from 150 samples collected in 100 different localities in the surveyed area. The identified species include three new records (Andricus melikai Pujade-Villar & Kwast, 2002; A. pseudocecconii Melika, Tavakoli & Stone, 2022; Saphonecrus undulatus (Мауr, 1872)) for the Turkish cynipid fauna. As a result of this study, 44 species of the current Turkish cynipid fauna were recorded from Burdur province for the first time. A checklist of the species and their host plants and/or host galls recorded in the study area is provided. The gall wasp richness and geomorphic-topographic structure of Burdur province is discussed.

Extinction Threat to a Previously Undescribed Species of Gall Wasp (Hymenoptera: Cynipidae) and Two Associated Parasitoid Species (Hymenoptera: Braconidae and Eulophidae) on a Threatened Rose

Diplolepis ogawai Abe and Ide sp. nov. (Hymenoptera: Cynipidae) induces galls on Rosa hirtula (Regel) Nakai (Rosales: Rosaceae), which is endemic to a restricted area of Honshu, the main island of Japan. The gall is induced mainly on the leaf of R. hirtula in spring and the mature gall falls to the ground in early summer. The gall-inducing wasp emerges from the gall on the ground in the following spring, suggesting that D. ogawai is univoltine. From spring to summer, the braconid Syntomernus flavus Samartsev and Ku and the eulophid Aprostocetus sp. are parasitic on the larva of D. ogawai in the gall, and the adult wasp of both parasitoid species emerges from the gall on the ground in summer. For S. flavus, this is the first distribution record in Japan and the first host record. Since R. hirtula is threatened with extinction by succession and deforestation, D. ogawai and its two parasitoid wasp species are considered to be at risk of coextinction with the threatened rose. In the event that the population size of this rose species is further reduced, D. ogawai and its parasitoids may -become extinct prior to the extinction of R. hirtula. To conserve these three wasp species associated with R. hirtula, protection of remnant vegetation where individuals of this threatened rose species grow is necessary.

Extreme acidity in a cynipid gall: a potential new defensive strategy against natural enemies

The morphology of insect-induced galls contributes to defences of the gall-inducing insect species against its natural enemies. In terms of gall chemistry, the only defensive compounds thus far identified in galls are tannins that accumulate in many galls, preventing damage by herbivores. Intrigued by the fruit-like appearance of the translucent oak gall (TOG; Amphibolips nubilipennis, Cynipidae, Hymenoptera) induced on red oak (Quercus rubra), we hypothesized that its chemical composition may deviate from other galls. We found that the pH of the gall is between 2 and 3, making it among the lowest pH levels found in plant tissues. We examined the organic acid content of TOG and compared it to fruits and other galls using high-performance liquid chromatography and gas chromatography-mass spectrometry. Malic acid, an acid with particularly high abundance in apples, represents 66% of the organic acid detected in TOGs. The concentration of malic acid was two times higher than in other galls and in apples. Gall histology showed that the acid-containing cells were enlarged and vacuolized just like fruits mesocarp cells. Accumulation of organic acid in gall tissues is convergent with fruit morphology and may constitute a new defensive strategy against predators and parasitoids.

Antioxidant, Cytotoxicity, Apoptotic Properties of Extracts of Andricus sternlichti galls and Their Phenolic Characterisation by HPLC

Quercus L. galls have been used in Western and Eastern cultures for various diseases in traditional medicine. Galls are also used in the East for many purposes, including consumption as food, commercial inks, leather tanning. In the current study, Andricus sternlichti Bellido, Pujade-Villar & Melika, 2003 galls were extracted in different solvents. The possible antioxidant effects of gall extracts were determined using 7 different methods (β-carotene-linoleic acid assay, Phosphomolybdenum assay, DPPH and ABTS radical scavenging activity, CUPRAC and FRAP assay, Metal Chelating activity) to support each other. Total phenolic, flavonoid and tannin amounts of extracts are calculated by using standard curves. In addition, HPLC method used to characterize the phenolic component with 15 different standards. The MIA PaCa-2 cell lines was preferred to identify possible cytotoxic activities of galls. Expression of some genes (Bax, Bcl-2, FAS, BID, caspase-3, caspase-8, caspase-9, caspase-10, FADD, TRADD) role in the apoptosis was determined to investigate apoptotic effects of extracts. According the results, the gall extracts of A. sternlichti may be considered as a potential source of biological agents for their antioxidant capacity and rich bioactive compounds. The gall extracts exhibit antiproliferative activity via regulating expressions of apoptotic genes.

Plant Gall Diversity in Burned Semi-natural Grasslands in Japan

We surveyed woody plants, including oaks and chestnuts (Quercus L. and Castanea Mill.), and recorded the inhabiting galls induced by oak gall wasps (Hymenoptera: Cynipidae: Cynipini) at seven Japanese semi-natural grassland sites maintained by traditional regular burning with two of the seven abandoned grassland areas. Woody plants were established in all burned and abandoned grasslands. Oak species were found at four of the seven sites. In total, 15 types of cynipid galls were recorded at all four sites where oak species were found. However, the occurrence of species was site-specific for host trees and cynipid galls. Although a few ecological studies of oak gall wasps inhabiting grassland environments, which have rapidly decreased in recent decades, have been conducted, this study suggests that semi-natural grasslands may be potential habitats for oak gall wasps and their host trees, and we provide a checklist of oak gall wasps with host oak records in semi-natural grasslands throughout Japan.

A new species of Andricus Hartig, 1840 (Hymenoptera, Cynipidae) from China, with references to DNA taxonomy and Wolbachia infection

In the present paper, a new species of cynipid gall wasp, Andricuselodeoides Liu & Pang, is described from several provinces in southern China. The new species is closely related to the recently redescribed A.mairei (Kieffer, 1906). In addition to differences in adult and gall morphology, the new species is also readily separated by COI sequences, with a 6.2-8.9% genetic distance between populations of the new species and those of A.mairei. A contrasting difference in sex ratios was also observed between the two species, with A.elodeoides extremely female-biased (95.5-97.8% female) while A.mairei male-biased to more balanced (5.4-43.5% female). PCR screening for Wolbachia infection further revealed contrasting infection rates between populations of A.elodeoides and A.mairei: the Wolbachia infection rate was 0% in A.elodeoides and 100% in A.mairei. Cytoplasmic incompatibility induced by Wolbachia is proposed as a potential mechanism of speciation of the sympatric A.elodeoides and A.mairei.

Speciation in Nearctic oak gall wasps is frequently correlated with changes in host plant, host organ, or both

Quantifying the frequency of shifts to new host plants within diverse clades of specialist herbivorous insects is critically important to understand whether and how host shifts contribute to the origin of species. Oak gall wasps (Hymenoptera: Cynipidae: Cynipini) comprise a tribe of ∼1000 species of phytophagous insects that induce gall formation on various organs of trees in the family Fagacae-primarily the oaks (genus Quercus; ∼435 sp.). The association of oak gall wasps with oaks is ancient (∼50 my), and most oak species are galled by one or more gall wasp species. Despite the diversity of both gall wasp species and their plant associations, previous phylogenetic work has not identified the strong signal of host plant shifting among oak gall wasps that has been found in other phytophagous insect systems. However, most emphasis has been on the Western Palearctic and not the Nearctic where both oaks and oak gall wasps are considerably more species rich. We collected 86 species of Nearctic oak gall wasps from most of the major clades of Nearctic oaks and sequenced >1000 Ultraconserved Elements (UCEs) and flanking sequences to infer wasp phylogenies. We assessed the relationships of Nearctic gall wasps to one another and, by leveraging previously published UCE data, to the Palearctic fauna. We then used phylogenies to infer historical patterns of shifts among host tree species and tree organs. Our results indicate that oak gall wasps have moved between the Palearctic and Nearctic at least four times, that some Palearctic wasp clades have their proximate origin in the Nearctic, and that gall wasps have shifted within and between oak tree sections, subsections, and organs considerably more often than previous data have suggested. Given that host shifts have been demonstrated to drive reproductive isolation between host-associated populations in other phytophagous insects, our analyses of Nearctic gall wasps suggest that host shifts are key drivers of speciation in this clade, especially in hotspots of oak diversity. Although formal assessment of this hypothesis requires further study, two putatively oligophagous gall wasp species in our dataset show signals of host-associated genetic differentiation unconfounded by geographic distance, suggestive of barriers to gene flow associated with the use of alternative host plants.

New herb gall wasps from Iran (Hymenoptera: Cynipidae)

Five new gall wasp species, Aulacidea koeiana Melika, Tavakoli & Stone, sp. nov., A. lorestanica Melika, Tavakoli & Stone, sp. nov., A. piroziae Melika, Stone & Pujade-Villar, sp. nov., Phanacis strigosa Melika, Stone & Tavakoli, sp. nov., P. tavakolii Melika, Stone & Pujade-Villar, sp. nov. are described from Lorestan, Iran. Descriptions, diagnoses, plus information on biology and host associations are given for all new species, and we provide the first description of the male of Isocolus beheni Melika & Karimpour, 2008.  

Novel Gene Rearrangements in the Mitochondrial Genomes of Cynipoid Wasps (Hymenoptera: Cynipoidea)

Cynipoidea is a medium-sized superfamily of Hymenoptera with diverse lifestyles. In this study, 16 mitochondrial genomes were newly sequenced, 11 of which were the first obtained mitochondrial genomes in the family Liopteridae and four subfamilies (Anacharitinae, Aspicerinae, Figitinae, and Parnipinae) of Figitidae. All of the newly sequenced mitogenomes have unique rearrangement types within Cynipoidea, whereas some gene patterns are conserved in several groups. nad5-nad4-nad4L-nad6-cytb was remotely inverted and two rRNA genes were translocated to nad3 downstream in Ibaliidae and three subfamilies (Anacharitinae, Eucoilinae, and Parnipinae within Figitidae); two rRNA genes in Aspicerinae, Figitinae, and Liopteridae were remotely inverted to the cytb-nad1 junction; rrnL-rrnS was translocated to the cytb-nad1 junction in Cynipidae. Phylogenetic inference suggested that Figitidae was a polyphyletic group, while the Ibaliidae nested deep within Cynipoidea and was a sister-group to the Figitidae. These results will improve our understanding of the gene rearrangement of the mitogenomes and the phylogenetic relationships in the Cynipoidea.

Global phylogeny of the inquilinous gall wasp tribe Synergini (Hymenoptera: Cynipoidea: Cynipidae): first insights and establishment of a new cynipid tribe

Previous phylogenetic studies of the tribe Synergini were focused on Palaearctic material, in which the genus Synergus was recovered as monophyletic, despite evidence of non-monophyly when global sampling is considered. A global molecular phylogeny of Synergini, including sequenced material from Nearctic and Neotropical realms, is presented herein for the first time. We assembled DNA data for 120 specimens: 104 representing all genera belonging to Synergini, except for the rare monospecific genus Agastoroxenia (ingroup), and 16 belonging to five other tribes of Cynipidae (outgroup). We obtained sequences for four genes: cytochrome c oxidase subunit I (COI), cytochrome b (Cytb), 28S region D2 (28S D2) and 28S region D3 (28S D3). The evaluated analyses support the non-monophyly of both Saphonecrus and Synergus (with Nearctic and Neotropical Synergus resolved into three clades separated from the Palaearctic species), as well as the monophyly of the rest of the genera in Synergini. Furthermore, the results suggest that neither Saphonecrus s.s. nor Synergus s.s. are present in the New World. The future challenges to separate the clades of Saphonecrus and Synergus into new taxa are discussed. Lastly, Rhoophilus was shown to belong to a new tribe, Rhoophilini trib. nov., on the basis of molecular, morphological and biological data.

New species of Nearctic oak gall wasps (Hymenoptera: Cynipidae, Cynipini)

Twenty nine new species of cynipid oak gall wasps from the Nearctic region (America north of Mexico) are described: Andricus archboldi Melika & Abrahamson, sp. nov., A. catalinensis Melika, Nicholls & Stone, sp. nov., A. chapmanii Melika & Abrahamson, sp. nov., A. chiricahuensis Melika, Nicholls & Stone, sp. nov., A. coconinoensis Melika, Nicholls & Stone, sp. nov., A. columbiensis Melika, Nicholls & Stone, sp. nov., A. cooki Melika, Nicholls & Stone, sp. nov., A. fitzpatricki Melika & Abrahamson, sp. nov., A. highlandensis Melika, Nicholls & Stone, sp. nov., A. mellificus Nicholls, Stone & Melika, sp. nov., A. menkei Melika & Abrahamson, sp. nov., A. mogollonensis Melika, Nicholls & Stone, sp. nov., A. nichollsi Melika & Stone, sp. nov., A. schickae Nicholls, Melika & Stone, sp. nov., A. torreyaensis Melika & Abrahamson, sp. nov., A. williami Melika, Nicholls & Stone, sp. nov., Antron lovellae Melika, Nicholls & Stone, sp. nov., A.tomkursari Melika, Nicholls & Stone, sp. nov., Dryocosmus archboldi Melika & Abrahamson, sp. nov., Loxaulus virginianae Melika & Buss, sp. nov., Neuroterus alexandrae Nicholls & Melika, sp. nov., N. aliceae Melika, Nicholls & Stone, sp. nov., N. bussae Melika & Nicholls, sp. nov., N. oblongifoliae Nicholls, Stone & Melika, sp. nov., N. quaili Melika, Nicholls & Stone, sp. nov., N. rosieae Melika, Nicholls & Stone, sp. nov., N. stonei Melika & Nicholls, sp. nov., Zapatella abrahamsoni Melika, sp. nov., Z. brooksvillei Melika & Abrahamson, sp. nov.. Alternate asexual and sexual generations are described for four species, Andricus archboldi Melika & Abrahamson, sp. nov., A. fitzpatricki Melika & Abrahamson, sp. nov., A. schickae Nicholls, Melika & Stone, sp. nov., Neuroterus aliceae Melika, Nicholls & Stone, sp. nov.. Descriptions, diagnoses, plus information on biology and host associations are given for all new species. All taxa are supported by morphological data; matching of generations is established using DNA sequence data. We also demonstrate that Neuroterus niger var. alimas Kinsey should be considered as a nomen dubium.  

Ultraconserved elements-based systematics reveals evolutionary patterns of host-plant family shifts and phytophagy within the predominantly parasitoid braconid wasp subfamily Doryctinae

Phytophagy has promoted species diversification in many insect groups, including Hymenoptera, one of the most diverse animal orders on Earth. In the predominantly parasitoid family Braconidae, an association with insect-induced, plant galls in angiosperms have been reported in three subfamilies, but in particular in the Doryctinae, where it has been recorded to occur in species of ten genera. Allorhogas Gahan is the most species-rich of these genera, with its species having different phytophagous strategies. Here we conducted a comprehensive phylogenomic study for the doryctine gall-associated genera, with an emphasis on Allorhogas, using ultraconserved elements (UCEs). Based on this estimate of phylogeny we: (1) evaluated their taxonomic composition, (2) estimated the timing of origin of the gall-associated clade and divergence of its main subclades, and (3) performed ancestral state reconstruction analyses for life history traits related to their host-plant association. Our phylogenetic hypothesis confirmed Allorhogas as polyphyletic, with most of its members being nested in a main clade composed of various subclades, each comprising species with a particular host-plant family and herbivorous feeding habit. The origin of gall-association was estimated to have occurred during the late Oligocene to early Miocene, with a subsequent diversification of subclades during the middle to late Miocene and Pliocene. Overlap in divergence timing appears to occur between some taxa and their host-associated plant lineages. Evolution of the feeding strategies in the group shows "inquilinism-feeding" as the likely ancestral state, with gall-formation in different plant organs and seed predation having independently evolved on multiple occasions.

Catalogue of Rose Gall, Herb Gall, and Inquiline Gall Wasps (Hymenoptera: Cynipidae) of the United States, Canada and Mexico

Background

Cynipidae (Hymenoptera: Cynipoidea) is a diverse group of wasps, many of which are capable of inducing plants to make galls, novel structures that protect and nourish the wasps' larvae. Other cynipids, especially those species in Ceroptresini and Synergini, are understood to be usurpers of galls made by other cynipids. The North American cynipid fauna has not been fully catalogued since 1979, but there is renewed interest in revising the taxonomy and in doing research that sheds light on the mechanisms of gall induction, the evolution of this life history, and their ecological interactions more broadly. Significant taxonomic changes have impacted the group since 1979, thereby warranting a new catalogue.

New information

The current state of knowledge of species classified in Aulacideini, Ceroptresini, Diastrophini, Diplolepidini, Phanacidini and Synergini in the United States, Canada, and Mexico is summarised in catalogue format. We report 323 names, including 170 valid species of rose gall wasps, herb gall wasps, and inquiline gall wasps, classified in 12 genera, from the United States, Canada, and Mexico. Current taxonomic status, distribution, host associations, and vernacular names are listed for each species. The catalogue also includes the original description of galls for many species of gall-inducer, as well as atomised characterisations of different gall traits as key-value pairs. For most galling species without existing vernacular names, new vernacular names are proposed.

Design and Testing of Effective Primers for Amplification of the orf7 Gene of Phage WO Associated with Andricus hakonensis

Simple Summary

Andricus hakonensis is thought to contain the most complex and diverse phage types known and should be an ideal model material for studying interactions among bacteriophages, bacteria and eukaryotes. As shown in previous studies, existing primers are not effective enough to amplify all virus groups in A. hakonensis. Based on a comprehensive analysis of all virus groups reported to date, we designed a relatively conservative primer for virus detection. This primer can accurately and efficiently detect the presence of phage WO in arthropod hosts. Using gene alignment, clear evidence was provided for the existence of hitherto unreported base deletions, which are an important cause of diversity in phage WO associated with A. hakonensis.

Abstract

Phage WO was first characterized in Wolbachia, an obligate intracellular Rickettsiales known for its ability to regulate the reproduction of arthropod hosts. In this paper, we focus on the study of virus diversity in Andricus hakonensis and the development of highly effective primers. Based on the existing Wolbachia genome sequence, we designed primers (WO-TF and WO-TR) to amplify the full-length orf7 gene of phage WO. Surprisingly, sequencing results showed a high abundance of other phage WO groups in A. hakonensis, in addition to the four groups previously identified. The results also showed that A. hakonensis contained most of the known types of orf7 genes (I, III, IV, V and VI) and the level of diversity of harbored phage WO was very high. Therefore, we speculated that existing primers were not specific enough and that new primers for the detection of phage WO were needed. Based on the existing orf7 gene sequence, we designed specific detection primers (WO-SUF and WO-SUR). Sequencing results showed that the primers effectively amplified all known types of phage WO. In addition to amplifying most of the known sequences, we also detected some new genotypes in A. hakonensis using the new primers. Importantly, all phage WO groups could be efficiently detected. Combined with the results of previous studies, our results suggest that A. hakonensis contains the largest number of phage types (up to 36 types). This study is novel in that it provides practical molecular evidence supporting base deletions, in addition to gene mutations and genetic recombination, as an important cause of phage WO diversity.

A new genus of Nearctic oak gall wasp, Grahamstoneia Melika amp; Nicholls, gen. nov. (Hymenoptera: Cynipidae, Cynipini)

A new genus, Grahamstoneia Melika Nicholls, gen. nov., with one new species, G. humboldti Melika Nicholls, sp. nov., asexual generation, is described. This new taxon occurs in the south-western Nearctic, inducing galls on two species within Quercus section Protobalanus (Q. vacciniifolia Kellogg and Q. chrysolepis Liebm.), an ecology and distribution shared with the closely related genus Heteroecus Kinsey. Descriptions, diagnoses, biology, and host associations for the new genus and species are given. The new taxon is supported by morphological and molecular data.

A Case of Intragenic Recombination Dramatically Impacting the Phage WO Genetic Diversity in Gall Wasps

The phage WO was characterized in Wolbachia, a strictly intracellular bacterium causing several reproductive alterations in its arthropod hosts. This study aimed to screen the presence of Wolbachia and phage WO in 15 gall wasp species from six provinces of southern China to investigate their diversity and prevalence patterns. A high incidence of Wolbachia infection was determined in the gall wasp species, with an infection rate of 86.7% (13/15). Moreover, seven species had double or multiple infections. All Wolbachia-infected gall wasp species were found to harbor phage WO. The gall wasp species infected with a single Wolbachia strain were found to harbor a single phage WO type. On the contrary, almost all species with double or multiple Wolbachia infections harbored a high level of phage WO diversity (ranging from three to 27 types). Six horizontal transfer events of phage WO in Wolbachia were found to be associated with gall wasps, which shared identical orf7 sequences among their respective accomplices. The transfer potentially took place through gall inducers and associated inquilines infected with or without Wolbachia. Furthermore, 10 putative recombination events were identified from Andricus hakonensis and Andricus sp2, which harbored multiple phage WO types, suggesting that intragenic recombination was the important evolutionary force, which effectively promoted the high level of phage WO diversity associated with gall wasps.

Ecology and Evolution of Gall-Inducing Arthropods: The Pattern From the Terrestrial Fossil Record

Insect and mite galls on land plants have a spotty but periodically rich and abundant fossil record of damage types (DTs), ichnotaxa, and informally described gall morphotypes. The earliest gall is on a liverwort of the Middle Devonian Period at 385 million years ago (Ma). A 70-million-year-long absence of documented gall activity ensues. Gall activity resumes during the Pennsylvanian Period (315 Ma) on vegetative and reproductive axial organs of horsetails, ferns, and probably conifers, followed by extensive diversification of small, early hemipteroid galler lineages on seed-plant foliage during the Permian Period. The end-Permian (P-Tr) evolutionary and ecological crisis extinguished most gall lineages; survivors diversified whose herbivore component communities surpassed pre-P-Tr levels within 10 million years in the mid-to late Triassic (242 Ma). During the late Triassic and Jurassic Period, new groups of galling insects colonized Ginkgoales, Bennettitales, Pinales, Gnetales, and other gymnosperms, but data are sparse. Diversifying mid-Cretaceous (125–90 Ma) angiosperms hosted a major expansion of 24 gall DTs organized as herbivore component communities, each in overlapping Venn-diagram fashion on early lineages of Austrobaileyales, Laurales, Chloranthales, and Eurosidae for the Dakota Fm (103 Ma). Gall diversification continued into the Ora Fm (92 Ma) of Israel with another 25 gall morphotypes, but as ichnospecies on a different spectrum of plant hosts alongside the earliest occurrence of parasitoid attack. The End-Cretaceous (K-Pg) extinction event (66 Ma) almost extinguished host–specialist DTs; surviving gall lineages expanded to a pre-K-Pg level 10 million years later at the Paleocene-Eocene Thermal Maximum (PETM) (56 Ma), at which time a dramatic increase of land surface temperatures and multiplying of atmospheric pCO2 levels induced a significant level of increased herbivory, although gall diversity increased only after the PETM excursion and during the Early Eocene Climatic Optimum (EECO). After the EECO, modern (or structurally convergent) gall morphotypes originate in the mid-Paleogene (49–40 Ma), evidenced by the Republic, Messel, and Eckfeld floras on hosts different from their modern analogs. During subsequent global aridification, the early Neogene (20 Ma) Most flora of the Czech Republic records several modern associations with gallers and plant hosts congeneric with their modern analogs. Except for 21 gall DTs in New Zealand flora, the gall record decreases in richness, although an early Pleistocene (3 Ma) study in France documents the same plant surviving as an endemic northern Iran but with decreasing associational, including gall, host specificity.

Chromosomes of three gall wasps of the tribe Aylacini (Hymenoptera, Cynipidae)

Chromosomes of two species of the tribe Aylacini (Cynipidae), Isocolus jaceae (Schenck, 1863) and I. scabiosae (Giraud, 1859) (both have 2n = 18) were studied for the first time. In addition, 2n = 20 is confirmed in a member of the same tribe, Aulacidea hieracii (Bouché, 1834). All chromosomes of these gall wasps are biarmed; however, they gradually decrease in size in the case of A. hieracii, whereas a pair of large metacentrics is characteristic of karyotypes of both Isocolus Förster, 1869 species. Chromosomes of the two latter gall wasps are either metacentric or submetacentric, but elements with lower centromeric indices prevail in the karyotype of A. hieracii. Chromomycin A₃ (CMA₃)/DAPI staining revealed single CMA₃-positive bands on a particular pair of chromosomes of all species, and these bands apparently refer to the nucleolus organizing regions (NORs). However, localization of CMA₃-positive bands differs substantially between the studied members of Isocolus and Aulacidea Ashmead, 1897. Together with normal haploid and diploid mitotic divisions, several metaphase plates with 2n = 17 containing a peculiar dicentric chromosome were found in a single male specimen of I. scabiosae; this appears to be the first report of an obvious dicentric in the order Hymenoptera in general. Certain aspects of the chromosome diversity and karyotype evolution within the family Cynipidae and the tribe Aylacini in particular are briefly discussed.

Molecular Identification of Trissolcus japonicus, Parasitoid of the Brown Marmorated Stink Bug, by Species-Specific PCR

The samurai wasp, Trissolcus japonicus (Ashmead), has been proposed as a biocontrol agent against brown marmorated stink bugs (BMSB), due to its ability to parasitize and kill BMSB eggs. However, the wasps' small size makes it challenging for those untrained in morphological identification to determine the wasps' species. To circumvent this problem, a molecular method was created to identify T. japonicus. The method uses species-specific primers, designed in this study, which target the variable region of the mitochondrial Cytochrome Oxidase 1 (CO1) locus. After confirming successful DNA extraction from samples, the PCR amplification using our primers produced 227-bp PCR products for all T. japonicus specimens and no amplification in other microhymenoptera candidates. Additionally, DNA from BMSB-parasitized eggs gave positive PCR amplification, while the control BMSB samples showed no amplification. This indicates that PCR with our primers specifically and sensitively differentiates T. japonicus specimens from other similar wasp species and discriminates between T. japonicus-parasitized and non-parasitized BMSB eggs. Finally, an in silico analysis of CO1 sequences demonstrated that our primers match the sequences of four different haplotypes of T. japonicus, indicating that our diagnostic method could potentially be applied to analyze T. japonicus populations throughout North America, Europe, and parts of Asia.

A Taxonomic Review of the Gall Wasp Genus Saphonecrus Dalla-Torre and Kieffer and other Oak Cynipid Inquilines (Hymenoptera: Cynipidae) from Mainland China, with Updated Keys to Eastern Palaearctic and Oriental Species

After the examination of the oak cynipid inquilines deposited in the Parasitic Hymenoptera Collection of the Agriculture and Forestry University of Zhejiang (ZAFU, China), we provide a revision of the species of Saphonecrus, Lithosaphonecrus, Ufo (Hymenoptera: Cynipidae: Synergini) and Ceroptres (Hymenoptera: Cynipidae: Ceroptresini) found in mainland China. Two new species of Saphonecrus are described: S. albidus Lobato-Vila and Pujade-Villar, sp. nov. and S. segmentatus Lobato-Vila and Pujade-Villar, sp. nov. Four Saphonecrus species (S. gilvus Melika and Schwéger, 2015, S. globosus Schwéger and Tang, 2015, S. leleyi Melika and Schwéger, 2015, and S. nantoui Tang, Schwéger and Melika, 2015) are new records for this region. We also provide new data on the biology and distribution, redescriptions, illustrations and corrections to some of the species, as well as updated keys to Eastern Palaearctic and Oriental species of Saphonecrus and Ufo. Three species of Saphonecrus are considered to have an uncertain status: S. gemmariae (Ashmead, 1885) incertae sedis from the USA, S. excisus (Kieffer, 1904) nomen dubium from India, and S. sinicus Belizin, 1968 incertae sedis from China. The validity of Saphonecrus in the Nearctic region as well as the current status of S. serratus Weld, 1926 from the Philippines and S. favanus Weld, 1944 from the USA are discussed.

One hundred and sixty years of taxonomic confusion resolved: Belonocnema (Hymenoptera: Cynipidae: Cynipini) gall wasps associated with live oaks in the USA

Gall wasps (Hymenoptera: Cynipidae) in the genus Belonocnema induce galls on live oaks (Quercus series Virentes), forming multilocular root galls in the sexual generation and unilocular leaf galls in the asexual generation. Using morphological characters, host records, museum specimens, flight propensity and phylogenetic analysis of published cytochrome c oxidase subunit I (COI) and nuclear SNP data, we resolve the long-standing taxonomic confusion within Belonocnema and recognize three distinct species that are distributed throughout the southern and south-eastern USA: B. fossoria (rev. stat.), B. kinseyi (rev. stat.) and B. treatae, while B. quercusvirens is treated as species inquirenda. The presence of mitonuclear discordance results in the failure of a mitochondrial DNA barcode region to distinguish between B. fossoria and B. treatae, while recognizing B. kinseyi, despite the three species being clearly separated based on morphology and phylogenetic analysis of SNP data. We provide re-descriptions and an updated dichotomous key for both asexual and sexual generations of these widespread species. Finally, as Belonocnema has emerged as a model organism for ecological and evolutionary studies, we clarify the species examined in published studies to date.

Comprehensive phylogenomic analyses re-write the evolution of parasitism within cynipoid wasps

BACKGROUND

Parasitoidism, a specialized life strategy in which a parasite eventually kills its host, is frequently found within the insect order Hymenoptera (wasps, ants and bees). A parasitoid lifestyle is one of two dominant life strategies within the hymenopteran superfamily Cynipoidea, with the other being an unusual plant-feeding behavior known as galling. Less commonly, cynipoid wasps exhibit inquilinism, a strategy where some species have adapted to usurp other species' galls instead of inducing their own. Using a phylogenomic data set of ultraconserved elements from nearly all lineages of Cynipoidea, we here generate a robust phylogenetic framework and timescale to understand cynipoid systematics and the evolution of these life histories.

RESULTS

Our reconstructed evolutionary history for Cynipoidea differs considerably from previous hypotheses. Rooting our analyses with non-cynipoid outgroups, the Paraulacini, a group of inquilines, emerged as sister-group to the rest of Cynipoidea, rendering the gall wasp family Cynipidae paraphyletic. The families Ibaliidae and Liopteridae, long considered archaic and early-branching parasitoid lineages, were found nested well within the Cynipoidea as sister-group to the parasitoid Figitidae. Cynipoidea originated in the early Jurassic around 190 Ma. Either inquilinism or parasitoidism is suggested as the ancestral and dominant strategy throughout the early evolution of cynipoids, depending on whether a simple (three states: parasitoidism, inquilinism and galling) or more complex (seven states: parasitoidism, inquilinism and galling split by host use) model is employed.

CONCLUSIONS

Our study has significant impact on understanding cynipoid evolution and highlights the importance of adequate outgroup sampling. We discuss the evolutionary timescale of the superfamily in relation to their insect hosts and host plants, and outline how phytophagous galling behavior may have evolved from entomophagous, parasitoid cynipoids. Our study has established the framework for further physiological and comparative genomic work between gall-making, inquiline and parasitoid lineages, which could also have significant implications for the evolution of diverse life histories in other Hymenoptera.

Description of three new species of oak gallwasps of the genus Amphibolips Reinhard from Mexico (Hymenoptera, Cynipidae)

Three new species of oak gall wasps of the genus Amphibolips Reinhard, 1865 (Hymenoptera: Cynipidae: Cynipini) are described from Mexico: Amphibolipsmagnigalla Nieves-Aldrey & Castillejos-Lemus, Amphibolipskinseyi Nieves-Aldrey & Castillejos-Lemus and Amphibolipsnigrialatus Nieves-Aldrey & Castillejos-Lemus. The specimens of the first two species were representative of sexual generations and come from the State of Oaxaca, while only a female, collected in the State of Veracruz, is described for A.nigrialatus. The new species induces galls on Quercuszempoaltepecana and Q.sapotifolia (Fagaceae, section Lobatae, red oaks). Descriptions of the diagnostic morphological characteristics of the three species and a key for their identification are provided. The taxonomic relationships of the new species with other species of Amphibolips are discussed; the three new species are closely allied amongst themselves and are related to A.dampfi Kinsey, 1937. With the three newly-described species, the number of Amphibolips in Mexico is increased to 23.

From Inquilines to Gall Inducers: Genomic Signature of a Life-Style Transition in Synergus Gall Wasps

Gall wasps (Hymenoptera: Cynipidae) induce complex galls on oaks, roses, and other plants, but the mechanism of gall induction is still unknown. Here, we take a comparative genomic approach to revealing the genetic basis of gall induction. We focus on Synergus itoensis, a species that induces galls inside oak acorns. Previous studies suggested that this species evolved the ability to initiate gall formation recently, as it is deeply nested within the genus Synergus, whose members are mostly inquilines that develop inside the galls of other species. We compared the genome of S. itoensis with that of three related Synergus inquilines to identify genomic changes associated with the origin of gall induction. We used a novel Bayesian selection analysis, which accounts for branch-specific and gene-specific selection effects, to search for signatures of selection in 7,600 single-copy orthologous genes shared by the four Synergus species. We found that the terminal branch leading to S. itoensis had more genes with a significantly elevated dN/dS ratio (positive signature genes) than the other terminal branches in the tree; the S. itoensis branch also had more genes with a significantly decreased dN/dS ratio. Gene set enrichment analysis showed that the positive signature gene set of S. itoensis, unlike those of the inquiline species, is enriched in several biological process Gene Ontology terms, the most prominent of which is “Ovarian Follicle Cell Development.” Our results indicate that the origin of gall induction is associated with distinct genomic changes, and provide a good starting point for further characterization of the genes involved.

UCE data reveal multiple origins of rose gallers in North America: Global phylogeny of Diplolepis Geoffroy (Hymenoptera: Cynipidae)

Gall wasps in the genus Diplolepis Geoffroy are specialized herbivores that induce galls exclusively on roses. Despite their wide distribution across the Holarctic, little is known about their evolutionary history. Here we present the first phylogenomic tree of global Diplolepis reconstructed using Ultraconserved Elements (UCEs), resulting in a robust phylogeny based on 757 genes. Results support the existence of two principal clades: a Nearctic stem-galler clade, and a Holarctic leaf-galler clade that further splits into two Palearctic groups and one Nearctic group. This topology is congruent with a previous study based on the mitochondrial gene COI, an unexpected result given the common occurrence of mitonuclear discordance in closely related oak gall wasp lineages. Most Diplolepis species were recovered as reciprocally monophyletic, with some notable exceptions such as the D. polita and the D. ignota complex, for which species boundaries remain unresolved. Historical biogeographic reconstruction was unable to pinpoint the origin of Diplolepis, but confirms two independent incursions into the Nearctic. Ancestral state reconstruction analysis highlights the conservatism of gall location on the host plants, as shifts to different host organs are relatively rare. We suggest that Diplolepis were originally leaf gallers, with a Nearctic stem-galler clade undergoing a major plant organ switch onto rose stems. Host organ switch or reversal is uncommon, which suggests a level of conservatism. Our study showcases the resolving power of UCEs at the species level while also suggesting improvements to advance future Cynipoidea phylogenomics. Our results also highlight the additional sampling needed to clarify taxonomic relationships in the Nearctic and eastern Palearctic regions.

A new species of Periclistus Foerster, 1869 from China and review of the tribe Diastrophini (Hymenoptera, Cynipoidea, Cynipidae)

A new species of cynipid gall wasps, Periclistusorientalis Pang, Liu & Zhu, sp. nov., is herein described from Hunan, China in the tribe Diastrophini (Hymenoptera: Cynipoidea: Cynipidae). The phylogenetic relationship between Periclistus and all the other Diastrophini genera, except the recently described XestophanopsisPujade-Villar et al., 2019, was analyzed using a fragment of the mitochondrial COI gene and a fragment of the nuclear 28S gene. A taxonomic key to the known genera of Diastrophini and an updated taxonomic key to the known Eastern Palearctic species of Periclistus were provided. In addition, an updated checklist of the known species of the genus from the world is given.

A New Genus of Oak Gall Wasp, Striatoandricus Pujade-Villar (Hymenoptera: Cynipidae: Cynipini) from America with Descriptions of Two New Mexican Species

A new genus of cynipid oak gall wasp, Striatoandricus Pujade-Villar (Hymenoptera: Cynipidae: Cynipini), is described. Striatoandricus gen. nov. includes four previously described species, Andricus nievesaldreyi n. comb., A. georgei n. comb., A. maesi n. comb., and A. barriosi n. comb., which induce pubescent leaves or twig galls on Quercus belonging to Quercus section. Two new species from México are also described: S. cuixarti Pujade-Villar n. sp. and S. sanchezi Pujade-Villar n. sp. in Quercus section. Descriptions of the genus and diagnostic characters, including DNA sequence data, are presented. This new genus is supported by both morphological and molecular data.

A new Diplolepis Geoffroy (Hymenoptera, Cynipidae, Diplolepidini) species from China: a rare example of a rose gall-inducer of economic significance

A new species of the genus Diplolepis Geoffroy, Diplolepis abei Pujade-Villar & Wang sp. nov. is described on host plant Rosa sertata Rolfe × R. rugosa Thunb. from China with an integrative approach based on molecular and morphological data. Diagnosis, distribution and biology of the new species are included and illustrated. This species is the first known rose gall-inducer of economic importance. A review of Eastern Palearctic species of Diplolepis is given and a key to the Chinese fauna is presented.

Gall-Colonizing Ants and Their Role as Plant Defenders: From 'Bad Job' to 'Useful Service'

Galls are neoformed structures on host plant tissues caused by the attack of insects or other organisms. They support different communities of specialized parasitic insects (the gall inducers), and can also provide refuge to other insects, such as moths, beetles and ants, referred to as secondary occupants. This study focuses on galls induced by the oak gall wasp Andricus quercustozae and secondarily colonized by ants in a mixed oak forest. A field survey and two experiments were carried out to a) study ant (species-specific) preferences for different features of the galls, b) describe differences in gall architecture due to ant activity, c) analyse the effects of the presence of gall-dwelling ants on plant health. The results show that there are differences between ant species in gall colonization and in the alteration of gall opening and inner structure. We verified that gall-dwelling ants protect their host plants efficiently, offering them an indirect defence mechanism against enemies (predators and pathogens). The data suggest a new paradigm in ant–plant relationships mediated by the presence of galls on the plants whose ecological and evolutionary implications are discussed.

Genomic dissection of an extended phenotype: Oak galling by a cynipid gall wasp

Galls are plant tissues whose development is induced by another organism for the inducer's benefit. 30,000 arthropod species induce galls, and in most cases the inducing effectors and target plant systems are unknown. Cynipid gall wasps are a speciose monophyletic radiation that induce structurally complex galls on oaks and other plants. We used a model system comprising the gall wasp Biorhiza pallida and the oak Quercus robur to characterise inducer and host plant gene expression at defined stages through the development of galled and ungalled plant tissues, and tested alternative hypotheses for the origin and type of galling effectors and plant metabolic pathways involved. Oak gene expression patterns diverged markedly during development of galled and normal buds. Young galls showed elevated expression of oak genes similar to legume root nodule Nod factor-induced early nodulin (ENOD) genes and developmental parallels with oak buds. In contrast, mature galls showed substantially different patterns of gene expression to mature leaves. While most oak transcripts could be functionally annotated, many gall wasp transcripts of interest were novel. We found no evidence in the gall wasp for involvement of third-party symbionts in gall induction, for effector delivery using virus-like-particles, or for gallwasp expression of genes coding for plant hormones. Many differentially and highly expressed genes in young larvae encoded secretory peptides, which we hypothesise are effector proteins exported to plant tissues. Specifically, we propose that host arabinogalactan proteins and gall wasp chitinases interact in young galls to generate a somatic embryogenesis-like process in oak tissues surrounding the gall wasp larvae. Gall wasp larvae also expressed genes encoding multiple plant cell wall degrading enzymes (PCWDEs). These have functional orthologues in other gall inducing cynipids but not in figitid parasitoid sister groups, suggesting that they may be evolutionary innovations associated with cynipid gall induction.

Plant galls are induced by organisms that manipulate host plant development to produce novel structures. The organisms involved range from mutualistic (such as nitrogen fixing bacteria) to parasitic. In the case of parasites, the gall benefits only the gall-inducing partner. A wide range of organisms can induce galls, but the processes involved are understood only for some bacterial and fungal galls. Cynipid gall wasps induce diverse and structurally complex galls, particularly on oaks (Quercus). We used transcriptome and genome sequencing for one gall wasp and its host oak to identify genes active in gall development. On the plant side, when compared to normally developing bud tissues, young gall tissues showed elevated expression of loci similar to those found in nitrogen-fixing root nodules of leguminous plants. On the wasp side, we found no evidence for involvement of viruses or microorganisms carried by the insects in gall induction or delivery of inducing stimuli. We found that gall wasps express many genes whose products may be secreted to the host, including enzymes that degrade plant cell walls. Genome comparisons between galling and non-galling relatives showed cell wall-degrading enzymes are restricted to gall inducers, and hence potentially key components of a gall inducing lifestyle.

Host Specialization in Plant-galling Interactions: Contrasting Mites and Insects

Galling arthropods represent one of the most specialized herbivore groups. On an evolutionary scale, different taxa of insects and mites have convergently adapted to a galling lifestyle. In this study, we have used a multi-taxonomic approach to analyze the interaction specialization between gall-inducing mites and insects and their host plants in the Nitra City Park (Nitra, Slovakia). We used four ecological descriptors for describe plant-galling interactions: number of host plant species used by each arthropod species, galling specificity on host plant species (specificity), exclusivity of interactions between galling and plant species (specialization) and overlap of the interactions between arthropod species (similarity). We have found 121 species of gall-inducing arthropods, totaling 90 insects and 31 mites occurring on 65 host plant species. Our results reveal that mites have high specialization and low similarity of interactions in comparison to insects. A multiple-taxonomic comparison showed that these differences are triggered by gall-wasps (Hymenoptera: Cynipidae), the taxon with the lowest levels of specificity of plant-galling interactions (i.e., occurring on different host plant species). Our findings are indicative of different patterns of interaction between distinct gall-inducing arthropods taxa and their host plants, despite the ecological convergence of different taxa to a highly specialized herbivorous habitat.

Heterogony in Cycloneuroterus (Hymenoptera: Cynipidae: Cynipini) From Rearing Experiments and DNA Barcoding

Heterogony was confirmed in the cynipid genus Cycloneuroterus Melika and Tang in rearing experiments with DNA barcoding. These experiments involved Cycloneuroterus gilvus Tang and Melika, which was previously only described from the sexual generation adult. The first rearing experiment was conducted using unidentified asexual generation females collected from Quercus gilva Blume, and gall formation by the sexual generation offspring was confirmed on folded or unfolded young leaves of Q. gilva. The second experiment was conducted using sexual generation males and females reared from the leaf galls collected from Q. gilva, and gall formation by the asexual generation offspring was observed on leaves of Q. gilva. Based on the morphological features of the sexual generation adults and galls, this species was identified as C. gilvus. The species identity of wasp specimens of sexual and asexual generations used in the rearing experiments was cross-checked using DNA barcoding with the partial sequences of the cytochrome c oxidase subunit I (COI) region (658 bp). The asexual generation adult and gall of C. gilvus are described based on these results. The importance of 'closing the life cycle,' in this case a demonstration of heterogony, in oak gall wasps (Cynipini) is discussed.

Development of microsatellite markers for an outbreaking species of oak gall wasp, Zapatella davisae (Hymenoptera: Cynipidae), in the northeastern United States

Populations of the recently described black oak gall wasp, Zapatella davisae Buffington (Hymenoptera: Cynipidae), have been identified as the cause of extensive tree damage and mortality to black oaks, Quercus velutina Lamarck (Fagales: Fagaceae), in the northeastern United States. Relatively little is known, however, about the distribution, phylogenetic placement, and lifecycle of this important tree pest. Therefore, we conducted next-generation sequencing using the Ion Torrent™ PGM (ThermoFisher Scientific, Inc.) platform to develop genomic resources for the study of Z. davisae and for other closely related species of oak gall wasps. Individual sequence reads were aligned, assembled into unique contigs, and the contigs were then utilized for the in silico isolation and development of microsatellite markers. In total, we screened 36 candidate microsatellite loci, of which 23 amplified consistently (five polymorphic and 18 monomorphic). We then examined whether the polymorphic loci could be used to infer whether populations of Z. davisae from Cape Cod and Nantucket are sexual or asexual by calculating several metrics of genetic diversity that might indicate the mode of reproduction. These included testing for statistical deviations from Hardy-Weinberg equilibrium (HWE) and for linkage disequilibrium (LD), observations for the presence of the Meselson effect, and by calculating the probability that clonal individuals are more prevalent than would be expected in a randomly mating population. While we found significant deviations from HWE and more clonal individuals than expected, our estimates of the Meselson effect were inconclusive due to limited sampling, and we found no evidence of LD. Therefore, the sexual/asexual status of Z. davisae populations remains uncertain.