Gall Types Research Articles

Molecular phylogenetics and the evolution of host plant associations in the nematode genus Fergusobia (Tylenchida: Fergusobiinae)

Fergusobia nematodes (Tylenchida: Fergusobiinae) and Fergusonina flies (Diptera: Fergusoninidae) are putative mutualists that develop together in galls formed in meristematic tissues of many species of the plant family Myrtaceae in Australasia. Fergusobia nematodes were sampled from a variety of myrtaceous hosts and gall types from Australia and one location in New Zealand between 1999 and 2006. Evolutionary relationships of these isolates were inferred from phylogenetic analyses of the DNA sequences of the nuclear ribosomal DNA near-full length small subunit (up to 1689 bp for 21 isolates), partial large subunit D2/D3 domain (up to 889 bp for 87 isolates), partial mitochondrial cytochrome oxidase subunit I (618 bp for 82 isolates), and combined D2/D3 and mtCOI (up to 1497 bp for 66 isolates). The SSU data supported a monophyletic Fergusobia genus within a paraphyletic Howardula. A clade of Drosophila-associated Howardula, including Howardula aoronymphium, was the closest sequenced sister group. Phylogenetic analysis of sequences from D2/D3 and mtCOI, separately and combined, revealed many monophyletic clades within Fergusobia. The relationships inferred by D2/D3 and mtCOI were congruent with some exceptions. Well-supported clades were generally consistent with host plant species and gall type. However, phylogenetic analysis suggested host switching or putative hybridization events in many groups, except the lineage of shoot bud gallers on the broad-leaved Melaleuca species complex.

Minimal insect herbivory for the Lower Permian Coprolite Bone Bed site of north-central Texas, USA, and comparison to other Late Paleozoic floras

An examination of 598 leaves from the Lower Permian (late Sakmarian) Coprolite Bone Bed (CBB) site in north-central Texas, USA, reveals low herbivory levels based on analyses of foliar surface-area removed (0.25%) and frequency of herbivorized leaves (15.6%). These values contrast with a similar study from a somewhat younger (mid-Artinskian) nearby site where analogous values are 2.55% and 31.8%, respectively. As at the younger site, when compared to all other co-occurring plant taxa, CBB pteridosperms were overwhelmingly herbivorized, particularly the peltasperm Autunia cf. conferta and the medullosan Odontopteris cf. lingulata, the latter preserving an exceptionally high herbivory level of 3.31%. These two host-plant taxa accounted for 96.8% of all herbivorized leaves and 96.4% of all leaf surface area removed by insects. For the bulk flora, four subgroups of feeding were documented: margin feeding (70.1% of all occurrences), hole feeding (24.1%), and minor skeletonization (earliest occurrence), and galling. Distinctive gall types, one on the midveinal region of A. cf. conferta and the other on a branchlet of Walchia piniformis (also occurring in the European Early Permian) add to an existing but depauperate insect gall record for the Pennsylvanian and Permian. Emerging evidence indicates that herbivory intensity was spatiotemporally heterogeneous across fluvially-associated landscapes during the Early Permian in both western Euramerica (Texas, USA) and western Gondwana (Paraná Basin, Brazil), differing by an order of magnitude within each of these areas. Localities with the highest percentages of bulk leaf surface-area removed by herbivores in both realms ranged from 2.39 to 2.97%. This range approximates about a third of modern surface-area removal values by insect herbivores in both subtropical to tropical floras.

Diversity and biosystematics of gall-inducing aphids (Hemiptera: Aphididae) and their galls in the Himalaya

Aphids (Hemiptera) are one of the important groups that induce galls on plants. A review of the gall-inducing aphids and aphid-induced galls in the Himalaya has been made. Altogether, 76 aphid species belonging to the subfamilies Aphidinae, Drepanosiphinae, Eriosomatinae, and Hormaphidinae induce galls both of cataplasmic and prosoplasmic nature on different plant species in the Himalaya. Gall-inducing aphids mostly occur in the Western and Northwestern Himalaya and 33 species are endemic to the Himalaya. Although the specific gall-inducing generation and the galls on the primary host do not occur in the Eastern Himalaya, some aphids that are capable to induce galls elsewhere occur on secondary host plants in that area. Various types of galls on leaves and stems occur. Generally gall-inducing aphids and their host plants are species specific. A few host plants, for examples, Populus ciliata, Prunus cornuta, Pistacia integerrima, Ulmus spp. harbor more than one gall-inducing aphid. Although gall-inducing aphids are mostly holocyclic and heteroecious, a few species such as Hamamelistes miyabei, Hayhurstia atriplicis, Pemphigus siphunculatus, Pterocallis afflnis, Thecabius qffinis, Tinocalloides montanus, are autoecious. Two-year cycle has been observed in some species of Fordini. Resource partitioning among species occurring on the same host plant has also been observed. A few pemphigine species have soldier morphs involved in either gall defense or territorial fighting for selection of gall-site and protecting galls from the invasion of other clones and cleaning the galls. Trophic relationship of aphids and their galls shows that throughout the growth period aphids obtain a steady supply of nutrients. Accumulation of phenolic compounds above a threshold level plays an important role in the immigration of aphids from the galls. Natural enemies associated with gall-inducing aphids are few and that on prosoplasmic galls induced by the species of Baizongia, Epipemphigus, Forda, Kaltenbachiella, Pemphigus, Tetraneura, are limited. Out of the 24 hymenopteran parasitoids known, 9 species are endemic in the Himalaya. In comparison, all predators are non-specific and none is endemic. Predators include cocconellids (13 species), neuropterans (6 species), anthocorieds (7 species), and syrphids (5 species). Biological studies on these natural enemies have also been reviewed.

Gall morpho-type corresponds to separate species of gall-inducing thrips (Thysanoptera: Phlaeothripidae)

CSIRO Entomology, GPO Box 1700, Canberra ACT 2601, AustraliaReceived 13 December 2004; accepted for publication 5 December 2005Kladothrips rugosus Froggatt has previously been considered a single polyphagous species that, in Australia,induces galls on several species of Acacia, with the gall structure varying both within and between hosts. On Acaciapapyrocarpa, two types of gall are induced by this species, one with the surface ridged but the other with the surfacesmooth. Using sequence data from cytochrome oxidase subunit I (CO I) and elongation factor-1 alpha gene frag-ments, we show that the thrips inducing these two gall-types are genetically distinct and comprise separate lineages.Uncorrected ‘ p’ distances calculated from CO I gene fragments were 0.000 and 0.006 within lineages and 0.074 and0.078 between lineages. The between-lineage distances are comparable with distances between morphologically dis-tinct species of other Acacia gall-thrips. Re-examination of adult thrips from the two gall types revealed consistentdifferences in body colour, as well as in body sculpture. Together with observations on gall founding behaviour, thesedata indicate that the thrips populations in the two gall types on A. papyrocarpa are reproductively isolated andshould be considered as separate species. The form from smooth galls on A. papyrocarpa is therefore described asKladothrips nicolsoni sp. nov., although the form from ridged galls can be considered only as ‘K. rugosus agg.’.These inconsistencies in the taxonomic status of the various units within the K. rugosus species complex are dis-cussed, although most of them cannot be distinguished morphologically at present. © 2006 The Linnean Society ofLondon, Biological Journal of the Linnean Society, 2006, 88, 555–563.

Comparative anatomy of gall development on Gypsophila paniculata induced by bacteria with different mechanisms of pathogenicity

Galls induced on Gypsophila paniculata by Pantoea agglomerans pv. gypsophilae (Pag) and Agrobacterium tumefaciens (At), bacteria with different mechanisms of pathogenicity, were compared morphologically and anatomically. The pathogenicity of Pag is dependent on the presence of an indigenous plasmid that harbors hrp gene cluster, genes encoding Hop virulence proteins and biosynthetic genes for auxin (IAA) and cytokinins (CKs), whereas that of At involves host transformation. The Pag-induced gall was rough, brittle and exhibited limited growth, in contrast to the smooth, firm appearance and continuous growth of the At-induced gall. Anatomical analysis revealed the presence of cells with enlarged nuclei and multiple nucleoli, giant cells and suberin deposition in Pag that were absent from At-induced galls. Although circular vessels were observed in both gall types, they were more numerous and the vascular system was more organized in At. An aerenchymal tissue was observed in the upper part of the galls. Ethylene emission from Pag galls, recorded 6 days after inoculation, was eight times as great as that from non-infected controls. In contrast, a significant decrease in ethylene production was observed in Gypsophila cuttings infected with Pag mutants deficient in IAA and CK production. The results presented are best accounted for by the two pathogens having distinct pathogenicity mechanisms that lead to their differential recognition by the host as non-self (Pag) and self (At).

Resource partitioning and exploitative competition in stem‐galling midges mediated by the host plant

Abstract Izeniola obesula Dorchin and Stefaniola defoliata Dorchin (Diptera, Cecidomyiidae) are two cecidomyiid species inducing multichambered galls in young shoots of the salt marsh plant, Suaeda monoica Gmelin (Chenopodiaceae). The purpose of this work was to study the relationship between the two species, which co‐occur in time and space, and may therefore potentially compete for plant resources.Characterization of the resources available to ovipositing females revealed that shoots in apical positions are more vigorous than shoots in basal positions, but that the two species of gall midges react to this variability of resources in different ways, as reflected by the patterns of gall distribution. Izeniola obesula galls were primarily induced in the younger, more rapidly growing shoots, whereas those of S. defoliata were predominantly induced in older, less vigorous shoots. Nevertheless, despite the general partitioning of resources, a certain amount of niche overlap was found, resulting in the occasional induction of an S. defoliata gall proximal to that of I. obesula in the same shoot. Co‐occurrence of the two types of galls in time and space did not have apparent effect on S. defoliata galls, but did have a strong adverse impact on young I. obesula galls, 60% of which were killed without producing adult midges, and the remaining 40% produced a much smaller number of adults. These effects are attributed to asymmetric interspecific competition that is mediated by the plant, resulting from the difference in stem tissues utilized by the larvae of the two species. It is concluded that preponderance of vacant niches, low densities of galls, and small niche overlap between the species do not preclude the occurrence of interspecific exploitative competition in this system, although its role in shaping the populations of the species is limited.

Morphogenesis of galls induced by Baccharopelma dracunculifoliae (Hemiptera: Psyllidae) on Baccharis dracunculifolia (Asteraceae) leaves

The commonest insect gall on Baccharis dracunculifolia (Asteraceae) leaves is induced by Baccharopelma dracunculifoliae (Hemiptera, Psyllidae). The gall-inducing insect attacks young leaves in both the unfolded and the fully expanded stages. Four developmental phases were observed in this type of gall: 1) A folding phase, during which the leaf lamina folded upward alongside the midrib and the edges of the upper portion of the leaf approached each other, forming a longitudinal slit. A single chamber was formed on the adaxial surface of the leaf; 2) A swelling phase, in which the folded leaf tissues thickened and the edges of the leaf drew closer together, narrowing the slit. In this phase the gall matured, turning succulent, fusiform and pale green. The single nymphal chamber was lined with white wax and was able to house from one to several nymphs; 3) A dehiscence phase, characterized by the opening of the slit to release inducers; and 4) A senescence phase, when the gall turned dark and dry. The dermal system of the mature gall was composed of a single-layered epidermis. The mesophyll was swollen, and the swelling was due mainly to hyperplasia of the parenchyma. The vascular tissues along the midrib vein were conspicuous and the perivascular fibers resembled parenchymal cells. The hypertrophied secretory cavities contained low lipophylic content. This gall does not form nutritive tissue, but salivary sheaths left by the inducers were observed near the parenchyma, vascular bundles and secretory cavities. This study complements our current knowledge of gall biology and sheds further light on the plasticity of plant tissues stimulated by biotic factors.

Adaptive radiation of gall-inducing insects

Summary The adaptive radiation of four taxa of gall-inducing insects is compared: sawflies (Hymenoptera: Tenthredinidae), oak gall wasps (Hymenoptera: Cynipidae), aphids (Homoptera: Aphididae), and gall midges (Diptera: Cecidomyiidae). The sawflies, with only three genera but many species per genus, colonized many adaptive zones. Many sibling species have been recently recognized. Such characteristics suggest a dynamic evolutionary state of radiation. Innovations in the substrates used for oviposition by sawflies, probably involving ovipositional accidents, have enabled evolution from free-feeding ancestors into diverse gall types and galling sites – from leaf edge to leaf lamina, leaf midrib, petiole, bud, and stem. Host shifting among species of willows (Salix) has been extensive and opportunistic. The oak gall wasps, like the sawflies, colonized many adaptive zones, in terms of galling sites on the plant and diverse gall types. The gall wasps include large genera, and use a geographically widespread host-plant genus rich in species, with largely opportunistic colonization of new hosts. The gall-inducing aphids on Pistacia in Israel show radiation into many adaptive zones, with different gall types and galling sites on the host plant, even though the radiation is much less extensive than in sawflies and gall wasps. A major limiting factor in this smaller radiation appears to be the low richness of Pistacia species and the host specificity of the galling aphids to this plant genus. The gall midges are similar to the sawflies and gall wasps with many large genera. Their radiation is much greater than in the related fungus-feeding midges, indicating the importance of a rich host flora for insect radiation. The study of adaptive radiation in gall-inducing insect taxa offers many opportunities for comparative studies in evolutionary biology.

Nine new species of Dasineura (Diptera: Cecidomyiidae) from flowers of Australian Acacia (Mimosaceae)

Abstract. Thirteen species of Australian acacias are invasive plants in agricultural and native vegetation areas of South Africa. Biological control programmes for Australian acacias in South Africa have been implemented and are aimed at suppressing reproductive vigour and, in some cases, vegetative growth of these weeds. Gall‐forming midges are under consideration as potential biological control agents for invasive acacias in South Africa. Entomological surveys in southern Australia found a diverse cecidomyiid fauna associated with the buds, flowers and fruits of Acacia species. Nine new Dasineura species are described and two species, D. acaciaelongifoliae (Skuse) and D. dielsi Rübsaamen, are redescribed. The newly described taxa are D. fistulosasp.n., D. furcatasp.n., D. glaucasp.n., D. glomeratasp.n., D. oldfieldiisp.n., D. oshanesiisp.n., D. piliferasp.n., D. rubiformissp.n. and D. sulcatasp.n. All eleven species induce galls on ovaries and prevent the formation of fruit. Two general types of gall are caused. Type A comprises woody, tubular galls with larvae living inside ovaries (D. acaciaelongifoliae, D. dielsi, D. fistulosa, D. furcata, D. glauca, D. glomerata, D. oldfieldii). Type B includes soft‐tissued, globose galls that belong to four subtypes: inflated, baglike, hairy galls with larvae living between ovaries (D. pilifera); pyriform, pubescent swellings with larvae living inside ovaries (D. rubiformis); globose, hairy, swellings with larvae living superficially on ovaries in ovoid chambers (D. oshanesii); and inconspicuous, glabrous swellings with larvae living superficially on ovaries in shallow groovelike chambers (D. sulcata). The gall types are associated with a particular pupation pattern. In type A galls, larvae pupate within larval chambers in galls, whereas in type B galls pupation takes place between ovaries in galls or in the soil beneath the host tree. Gall midges responsible for the same general gall type are morphologically related and differ from species causing the other gall type. Phylogenetic analysis of a 410 bp fragment of the mitochondrial cytochrome b gene supports the division of the gall midge species into two groups except for D. sulcata, which appears as a subgroup of the group causing type A galls. The interspecific divergence values in group A species were between 0.5 and 3.9% with intraspecific divergence estimates of 0–0.2%. Gall midges causing type B galls had interspecific divergence values of 4.6–7.3% and intraspecific divergence values of 0–3.7%. Closely related biology and morphology together with low cytochrome b divergence estimates suggest a more recent speciation in group A when compared with species of group B. Dasineura rubiformis and D. dielsi are proposed as potential biological control agents for Acacia mearnsii De Wild. and Acacia cyclops A. Cunn. ex G. Don, respectively, in South Africa due to their narrow host range and ability to form high population densities that reduce seed formation. Both species produce galls with low biomass, which makes them compatible with commercial exploitation of their host species in Africa.

Anatomy of Cranberry Stem Gall and Localization of Bacteria in Galls

ABSTRACT Cranberry stem gall is characterized by tumors that girdle stems, thereby killing all distal leaves, flowers, and fruit. Bacteria that produce high levels of the plant growth hormone indole-3-acetic acid (IAA) are associated with and believed to cause cranberry stem gall. The anatomy of naturally occurring galls on woody cranberry plants and galls caused by inoculation of micropropagated cranberry plants with Pantoea agglomerans strain 4/99 was consistent with elevated levels of IAA in plants. Field galls exhibited hypertrophy and hyperplasia of tissue external to the vascular cambium, resulting in extensive stem swelling and splitting of the periderm. Similarly, galls on micropropagated plants contained enlarged cortical parenchyma cells. The current year's xylem vessels in field galls were narrow and dense compared with xylem vessels of healthy stems. Curved xylem elements apparently developed de novo within field galls and galls on inoculated plants. Cavities and fissures in both types of galls contained dense aggregates of bacteria. Treatment of micropropagated plants with synthetic IAA caused hypertrophy of cortical parenchyma and formation of adventitious roots. The results support the hypothesis that IAA-producing bacteria cause cranberry stem gall.

Response of a gall wasp community to genetic variation in the host plant Quercus crispula: a test using half-sib families

Abstract The structure of a herbivore community may change consistently along the genetic cline of a host plant, change at particular points along the cline, or respond independently of the cline. To reveal such relationships between a gall wasp community and genetic variation in the host plant Quercus crispula, we examined patterns in the species richness and abundance of gall wasps along a genetic cline of the host plant, using 12 half-sib families from six different regions. The genetic relationships among the half-sib families of Q. crispula were quantified on the basis of leaf morphology, which represented a morphological cline from leaves typical of Q. crispula to leaves resembling another oak species, Q. dentata. The morphological cline could be regarded as a genetic cline caused by a history of hybridization with Q. dentata. The mean numbers of gall types varied among the half-sib families, but did not show a consistent increase or decrease along the genetic cline. This pattern could be explained by the fact that responses to host plant variation differed among the gall wasp species. The half-sib families were classified into three groups based on an ordination analysis of the species composition of the gall wasp community that to some extent also reflected the genetic cline of Q. crispula. This suggests that the species composition of gall wasps changed intermittently along the genetic cline, rather than gradually and consistently along the cline.

Host range and host preference of a flea weevil, Orchestes hustachei, parasitizing aphid galls

Although larvae of flea weevils (Curculioninae: Rhamphini) have been known to be leaf miners, larvae of the rhamphine weevil Orchestes hustachei have been found in aphid galls of four Tetraneura species on Ulmus davidiana and in galls of Paracolopha morissoni on Zelkova serrata. This study clarified the feeding habits of O. hustachei larvae and evaluated gall selection by ovipositing females to test the hypothesis of host race formation on their hosts, Tetraneura and Paracolopha galls. When weevil larvae were placed in half-cut galls, they always fed on aphids rather than on gall tissue. When given gall tissue only, all larvae failed to reach adulthood. The number of aphids surviving in a parasitized gall decreased significantly with the development of the weevil larvae. These results suggest that O. hustachei larvae use aphids as their major food source. In the field, ovipositing females did not discern between four Tetraneura species on U. davidiana, in spite of a large difference in suitability as food. Paracolopha morrisoni was introduced into Hokkaido approximately 100 years ago, together with the host plant Z. serrata. It is probable that P. morrisoni has recently come to be used as a host by O. hustachei in Hokkaido. Host choice experiments using Tetraneura sp. O and P. morrisoni galls indicated that female weevils from Z. serrata preferred P. morrisoni to Tetraneura sp. O galls, while females from U. davidiana selected the two types of gall randomly. On Z. serrata, female weevils selected larger P. morrisoni galls, while on U. davidiana, females did not show a preference for gall size. These results suggest that a host shift to P. morrisoni galls may have led to an initial stage of host race formation between the weevil population using Tetraneura galls on U. davidiana, and that using P. morrisoni galls on Z. serrata.

The evolution of host plant manipulation by insects: molecular and ecological evidence from gall-forming aphids on Pistacia

One of the most striking characteristics of gall-forming insects is the variability in gall position, morphology, and complexity. Our knowledge of the driving forces behind the evolutionary divergence of gall types is limited. Natural enemies, competition, and behavioral constraints might be involved. We present a cladogram, based on sequences of COI and COII (1952 bp), of mitochondrial DNA for the evolution of 14 species of gall-forming aphids (Fordinae). These insects induce five gall types with remarkable morphological variation on Pistacia spp. hosts. The parsimony cladogram divides the Fordinae into three lineages, Fordini and Baizongiini, and a third (new) sister group including the previously Fordini member, Smynthurodes betae (West). We then use ecological data to trace and explain the evolution of gall morphology. The aphids seem to have evolved gradually towards better ability to manipulate their host plant, induce stronger sinks, and gain higher reproductive success. We suggest that the ancestral gall type was a simple, open, “pea”-sized gall located on the leaflet midvein. Some Fordini and S. betae evolved a two-gall life cycle, inducing a new gall type on the leaflet margin. The Baizongiini improved the manipulation of their host by inducing larger galls near the midvein, with stronger sinks supporting thousands of aphids. Similar gall types are induced at similar sites on different Pistacia hosts suggesting control of the aphids on gall morphology and frequent host shifts. Thus, even extreme specialization (specific gall and host) is flexible.

Occurrence and characterization of entomogen galls in plants from natural vegetation areas in Delfinópolis, MG, Brazil.

In the present work we aimed to register the occurrence of galls, inductors, inquilines, and parasitoids in plants of three natural vegetation areas in Delfinópolis, MG, Brazil. Results obtained showed 22 types of galls collected from leaf, vein leaf, petioles, stem, and inflorescence of nineteen species belonging to fifteen distinct families. Concerning gall morphology, the following were collected: globoid, conicle, discoidal, fusiform, shell-shape, indefinite, and one substituition of an ovary by an immature. As principal inducers were found insects of the families Cecidomyiidae (Diptera), Psyllidae, and Diaspididae (Sternorrhyncha/Hemiptera). As parasitoids the most common are of the Chalcidoidea superfamily (Hymenoptera) and, as occasional inquilines, Polyxenidae (Diplopoda) and Psocodea (Psocoptera). The results of this study contribute to existing of knowledge host-plant diversity and gall-associated insects in rocky fields, cerrado, and gallery forests.

Complex interactions envolving a gall midge Myrciamyia maricaensis Maia (Diptera, Cecidomyiidae), phytophagous modifiers and parasitoids

Myrciamyia maricaensis Maia, 1995 (Diptera, Cecidomyiidae) induces a gall in lateral and apical shoots in the plant Myrcia lundiana Kiaersk (Myrtaceae) which is used and modified by two eulophid wasps species. In both cases the gall former species suffer high rate of attack exceeding the importance of parasitoid species as mortality factors. In this study these interactions are described and their effects as mortality of gall former. The intensity of occurrence of the two eulophid species as modifiers and of microhymenopteran parasitoids, and the relative importance of these species as mortality agents of the M. maricaensis larvae is compared. This comparison reveals that two modifiers species found in the gall tissue modification causing the death of the M. maricaensis larva and it is a more important factor of mortality than the cecidomyiid larva parasitism. The fluctuation of the number of each type of gall along the year was monitored in the research field and confirmed in numerical and in synchronic terms of occurrence of the galls; the importance of the species of the gall modifier eulophids, particularly one of these species, as factors of mortality of the M. maricaensis larvae and justified our comparing the relationship between these species and M. maricaensis as similar to the parasitoid-host relationship. The gall shape modification by one of the eulophids allows the occurrence of other inquiline insect species, what means that this gall modification becomes it more heterogeneous and allows the increase of the species richness to the system.

Phylogeny of the Baldratiina (Diptera: Cecidomyiidae) inferred from morphological, ecological and molecular data sources, and evolutionary patterns in plant–galler relationships

The phylogeny of the gall-midge subtribe Baldratiina (Diptera: Cecidomyiidae) was reconstructed from molecular (partial sequence of the mitochondrial 12S rDNA), morphological and ecological data sets, using 16 representative species of most of the genera. The morphological and ecological data were combined in a single character matrix and analyzed separately from the molecular data, resulting in an eco-morphological cladogram and a molecular cladogram. Attributes of galls and host associations were superimposed on the molecular cladogram in order to detect possible trends in the evolution of these traits. The cladograms resulting from the two independent analyses were statistically incongruent, although both provide evidence for the monophyly of the genera Baldratia and Careopalpis and the paraphyly of the genera Stefaniola and Izeniola. The results suggest a minor impact of the morphological characters traditionally used in the classification of the Baldratiina, whereas ecological data had a major impact on the phylogenetic inference. Mapping of gall and host attributes on the molecular cladogram suggests that multi-chambered stem galls constitute the ancestral state in the subtribe, with several subsequent shifts to leaf galls. It is concluded that in contrast to other studied groups of gall insects, related baldratiine species induce different types of galls, attesting to speciation driven by gall-type shifts at least as often as host shifts.

Evolution of the gall-forming plant parasitic nematodes (Tylenchida: Anguinidae) and their relationships with hosts as inferred from Internal Transcribed Spacer sequences of nuclear ribosomal DNA

Phylogenetic relationships among gall-forming plant parasitic nematodes of the subfamily Anguininae are reconstructed by maximum parsimony and maximum likelihood analyses. Sequences of the ITS of rDNA from 53 populations and species of gall-forming nematodes and five populations of the Ditylenchus dipsaci species complex were analysed. The phylogenetic trees strongly support monophyly of the genus Anguina and show nonmonophyly for the genera Mesoanguina and Heteroanguina. Morphological and biological characters are generally congruent with the anguinid groups identified in the rDNA phylogeny. Analyses of evolution of different gall types among anguinids reveal that there are apparent evolutionary trends in gall evolution: from abnormal swelling and growth of infested plant organs toward small localised galls, and from infestation of vegetative toward generative organs. Our study demonstrates that the main anguinid groups are generally associated with host plants belonging to the same or related systematic groups. The comparison of the ITS phylogenies of anguinids parasitising Poaceae and their host grasses shows a high level of cospeciation events.

Gall-feeding habits in Lepidoptera of Japan. I : Three different types of galls

Gall-feeding habits in Lepidoptera of Japan. I : Three different types of galls

Morphogenesis of stem gall tissues induced by larvae of two cecidomyiid species (Diptera: Cecidomyiidae) onSuaeda monoica(Chenopodiaceae)

Izeniola obesula Dorchin and Stefaniola defoliata Dorchin (Diptera: Cecidomyiidae: Lasiopterini) are monophagous gall midges each inducing a unique kind of gall on stems of the salt marsh plant Suaeda monoica Gmelin (Chenopodiaceae). The morphogenesis of these two types of galls was studied in relation to the life history of the midges as observed both in the field and the laboratory. Izeniola obesula larvae penetrate the pith parenchyma through the growing shoot apex, causing intensive cell proliferation and inducing differentiation of novel vascular tissues and a sclerenchyma sheath around their chambers. Vascular differentiation in this gall originates from the larval chamber, a phenomenon attributed to local stimulation by the larva. It is suggested that the sclerenchyma layer in these galls is also induced by insect activity. Stefaniola defoliata larvae penetrate the stem laterally and reside inside the primary phloem, causing proliferation of phloem parenchyma, and are later encapsulated by secondary xylem tissue. Both galls are associated with a symbiotic fungus that grows along the inner walls of the larval chambers. The possible hormonal mechanisms controlling morphogenesis of the galls are discussed.Key words: gall morphogenesis, phytohormones, sclerenchyma, vascular differentiation.

Community structure, survival and mortality factors in arctic populations of Eupontania leaf gallers

We studied survival, mortality factors, and community structure of nine species of leaf-galling sawflies, Eupontania spp., living on ten willow species (Salix spp.) at six sites on the Russian arctic tundra. The sawfly species represented two different gall types: the viminalis-type, which forms pea-shaped galls on the underside of leaf blades, and the vesicator-type, which forms bean-shaped galls on both sides of the leaf blade. Gall communities in the northernmost site had only one parasitoid species, but up to six parasitoids were found at the southernmost site. Inquiline parasitoids were encountered only in the two southern sites. Survival of the larvae varied between 20.0 and 82.8% among galler species at different sites. Parasitoids were the most important mortality factor for the sawflies. They caused mortality of 7.8-65.4%, depending on galler species and site, and it was highest in the northernmost site. Plant-specific mortality varied from 1.7 to 28.4% by galler species and it tended to decrease towards the north. Mortality from parasitoids was greater in the vesicator-type gallers than in the viminalis-type gallers. The total mortality caused by parasitoids in the arctic communities does not appear to differ from that in the diverse southern communities of Eupontania in Middle Europe, Scandinavia and North America, despite the assemblage having only a few members in the Arctic. The largest difference between the southern and the northern communities was the lack of inquiline parasitoids in the north. Our data do not support the hypothesis that abiotic, rather than biotic, factors would be more important in determining the abundance of populations of herbivorous insects in the harsh arctic environment.