Gall‐forming insect species richness along a non‐scleromorphic vegetation rainfall gradient in South Africa: The importance of plant community composition

Abstract Currently there is no single accepted hypothesis to explain gall‐forming insect species richness at a particular locality. Hygrothermal stress, soil nutrient availability, plant species richness, plant structural complexity, plant family or genus size, and host plant geographical range size have all been implicated in the determination of gall‐forming insect species richness. Previous studies of such richness at xeric sites have included predominantly scleromorphic vegetation, usually on nutrient‐poor soils. This study is the first to investigate gall‐forming insect species richness of xeric, non‐scleromorphic vegetation. Two habitat types were sampled at each of five localities across a rainfall gradient in the savanna biome of South Africa. The habitat types differed with respect to plant species composition and topography. Gall‐forming insect species richness did not increase with increasing hygrothermal stress or decreasing soil fertility. Rather, gall‐forming insect species richness was largely dependent on the presence of Terminalia sericea as well as other members of the Combretaceae and Mimosaceae. Plots where all these taxa were present had the highest gall‐forming insect species richness, up to 15 species, whereas plots with none of these taxa had a maximum of four galling‐insect species. Despite herb, shrub and tree strata not differing in gall‐forming insect species richness, insect galls were more common on woody than non‐woody plants. Also, stem galls were more frequent than apical or leaf galls. An alternative hypothesis to explain local gall‐forming insect species richness is suggested: galling insects may preferentially select those plant species with characteristics such as chemical toxicity, mechanical strength, degree of lignification or longevity that can be manipulated to benefit the galler. Thus plant community composition should be considered when attempting to explain gall‐forming insect species richness patterns.     

Effects of host plant architecture on colonization by galling insects

Abstract: To study the abundance and occurrence of herbivore insects on plants it is important to consider plant characteristics that may control the insects. In this study the following hypotheses were tested: (i) an increase of plant architecture increases species richness and abundance of gall‐inducing insects and (ii) plant architecture increases gall survival and decreases parasitism. Two hundred and forty plants of Baccharis pseudomyriocephala Teodoro (Asteraceae) were sampled, estimating the number of shoots, branches and their biomass. Species richness and abundance of galling insects were estimated per module, and mortality of the galls was assessed. Plant architecture influenced positively species richness, abundance and survival of galls. However, mortality of galling insects by parasitoids was low (13.26%) and was not affected by plant architecture, thus suggesting that other plant characteristics (a bottom‐up pressure) might influence gall‐inducing insect communities more than parasitism (a top‐down pressure). The opposite effect of herbivore insects on plant characteristics must also be considered, and such effects may only be assessed through manipulative experiments.     

Direct and indirect interactions involving ants, insect herbivores, parasitoids, and the host plant Baccharis dracunculifolia (Asteraceae)

Abstract.  1. The relative importance of direct and indirect interactions in controlling organism abundance is still an unresolved question. This study investigated the role of the direct and indirect interactions involving ants, aphids, parasitoids, and the host plant Baccharis dracunculifolia (Asteraceae) on a galling herbivore Baccharopelma dracunculifoliae (Homoptera: Psyllidae).
2. The effects of these interactions on the galling herbivore's performance were evaluated by an exclusion experiment during two consecutive generations of the galling insect.
3. Ants had a direct negative effect on the performance of the galling herbivore by reducing the number of nymphs per gall. In contrast, ants had no indirect effects on gall mortality through the associated parasitoids.
4. Aphids negatively affected gall development, suggesting that galls and aphids might be partitioning photoassimilates and nutrients moving throughout host-plant tissues.
5. In addition, galls that developed during the rainy season were heavier, indicating that variation in the host plant, due to weather changes, can affect the development of B. dracunculifoliae galls. However, variation in the development of B. dracunculifoliae galls due to presence of aphids or the weather changes did not affect parasitoid attack.
6. These results suggest that direct interactions between ants and galls influenced galling insect abundance, whereas numerical indirect effects involving galling insects, ants, aphids, and host plants were less conspicuous.     

A plant pathogen causes extensive mortality in an invasive insect herbivore

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Host plant effects on the development and survivorship of the galling insect Neopelma baccharidis (Homoptera: Psyllidae)

In this study, the mortality factors acting upon the galling psyllid Neopelma baccharidis Burckhardt (Homoptera) caused by its host plant, Baccharis dracunculifolia De Candole (Asteraceae) were analysed. In March 1999, 982 galls of the same cohort were randomly marked on 109 individuals of B. dracunculifolia in the field. Galls were censused each month during their development, from April to August, and dead galls were collected and analysed for mortality factors. Gall dehiscence rates were calculated for each month. The major mortality source of N. baccharidis was gall dropping (13.2% of the original cohort), which is probably a normal outcome of previous mortality caused by the other factors observed in this study. Unknown factors killed 11.7% of this gall population and were ascribed to plant resistance during gall development. Empty galls represented 7.7% of the observed mortality and may be a consequence of egg retention or egg mortality/abortion related to variations in plant quality. Shoot mortality was high during the dry season and killed 7.5% of the galls, but this impact was minimized after the third month from gall formation due to the ability of nymphs to accelerate development and emerge from galls on dying shoots. However, the size of dehisced galls on dead shoots tended to be smaller, possibly affecting adult performance. Mortality of N. baccharidis attributed to B. dracunculifolia strongly controlled the galling insect population, killing 40.7% of the original cohort of galls. Plant‐mediated mortality was caused by often neglected factors acting predominantly during the first 3 months of development, which are critical to gall survivorship. These results reinforce the importance of bottom‐up forces in plant‐insect systems.     

Host plant intraspecific variation determines gall traits

• Galls display a multiplicity of traits, including colours, which are driven by pigment accumulation. Their conspicuousness has attracted researchers' attention and several hypotheses have been raised. However, plants themselves vary intra-specifically, including in their pigment concentrations. As galls are a result of host tissue development, colours may be a by-product of the host's own traits, being more conspicuous simply because the sites where galls develop already have the predisposition to accumulate more pigment. Here, we call this the host variation hypothesis.
• We test this hypothesis using the system of galls induced by Palaeomystella oligophaga on Macairea radula host plant. Using spectrophotometry, we calculated the Anthocyanin Reflectance Index (ARI) of gall projections, which are responsible for their characteristic colours. We tested the influence of occupant identity (galling insect or any natural enemy), gall volume, parenchyma thickness, height from the ground, ARI of leaf, ARI of gall surface and ARI of the respective stem.
• We corroborated the host variation hypothesis since the anthocyanin content in stems and in galls' projections were positively related. Moreover, anthocyanin in galls' projections was positively related to anthocyanin in the gall surface and negatively related to gall volume and parenchyma thickness. This shows that, besides the host specificities, galls' own traits may also be responsible for pigment accumulation, influencing their colours.
• In this study, using colour as an example, we show that although galls tend to be considered complex expressions of galling insects' stimuli, their traits may be simply influenced by previous and specific attributes of the host organs.

     

Hypersensitivity of Fagus sylvatica L. against leaf galling insects

Hypersensitivity is known as a localized resistance of plants against pathogens. It also can be detected in response to galling insects, i.e., in the area immediately adjacent to the site of oviposition and attempted penetration by the galling larva. This host response includes morphological and histological changes that cause the death of the attacked tissue. It is observed as a rounded dark brown halo around the gall induction site. We provide the first observation on the occurrence and possible relevance of this induced mechanism by which one of the most common tree species in Germany, Fagus sylvatica L., resists attack by two of its most common galling insects, Mikiola fagi and Hartigiola annulipes (Diptera: Cecidomyiidae). Galls induced by these cecidomyiids were extremely common in the studied area in beech forests around Darmstadt, Germany. The availability of resources (leaves on a stem) was a poor predictor of attack by the galling insects as well as for gall abundance (galls successfully formed). Hypersensitive reaction was the most important factor acting against the galling population studied. More than 77% of the attempts of the insects to induce galls on F. sylvatica resulted in failure and consequently the death of the galling larvae. Therefore, few live galls remained to be found and destroyed by natural enemies. This corroborates the view that in galling insect–host plant system interactions plant-driven factors may play a major role in determining herbivore failure and success, and perhaps the resulting community structure.     

Indirect competitive effects of stemborers on a gall community

Interspecific competition between phytophagous insects using the same host plant occurs frequently and can strongly affect population densities of competing species. Competition between gallmakers and stemborers could be especially intense because both types of herbivore are unable to avoid competition by relocation during their immature stages. For apical meristem gallmakers the main result of competition is likely to be the interruption of resources to the gall by the stemborers' devouring of stem contents. The proximate effect of such competition could be to reduce gall size, thereby increasing the number of chambers per gall unit volume, and reducing the size and potential reproductive output of the gallformer. In addition, smaller galls may be more susceptible to attack from size‐limited parasitoids, resulting in a second indirect effect of competition. Using a community of galling and stemboring insects on the saltmarsh shrub Iva frutescens L. (Asteraceae), we measured for indirect effects of competition. We examined the primary indirect effect of competition on gall midge crowding and the secondary effects on parasitism rates and parasitoid guild composition. Results indicated that galls co‐occurring with stemborers were smaller, crowding of gall inhabitants was 22% greater, and the composition of the parasitoid guild was altered relative to galls on unbored stems. The overall parasitism rate was not different between galls on bored vs. unbored stems. These results show that competition resulting from the presence of stemborers has the potential to affect the gall midge Asphondylia borrichiae Rossi & Strong (Diptera: Cecidomyiidae) and secondarily to affect its guild of hymenopteran parasitoids.     

Plant module size and dose of gall induction stimulus influence gall induction and galler performance

Several different hypotheses attribute large variations in gall abundance and galler performance to variations in plant growth rate and/or module size. The plant vigor hypothesis (PVH) predicts that galler performance will be greatest on large, fast‐growing plant modules due to their large, rapidly dividing cells that allow them to make large galls, where survival and size of survivors are usually greater. The optimal module size hypothesis (OMSH) predicts that galler performance will be greatest on intermediate‐sized modules, based on a tradeoff between ease of gall induction on small modules and increased resource availability in large modules. Here, we evaluate predictions of the PVH and OMSH during a two‐year field study by examining gall induction and full gall development success, as well as subsequent galler performance in successfully developed galls, using a shoot galling adelgid, Adelges abietis, on white spruce Picea glauca. In addition, we tested whether increased dose of gall induction stimulus on different sized modules, achieved by observing differing A. abietis densities per bud, could increase the rate of successful gall induction, as predicted by the OMSH. Galls of A. abietis appeared to be induced by a dose‐dependent stimulus from fundatrices in spring. Furthermore, the critical stimulus dose required to induce a gall appeared to increase with shoot length. These findings support the OMSH and not the PVH. Galler performance (gall volume and the number of gallicolae that emerged from each gall) in successfully developed galls was positively related to shoot length, supporting both the PVH and OMSH. We conclude that the PVH represents one component of the more inclusive OMSH, which considers both ease of gall induction on different‐sized modules and the effect of plant module size on gall size.     

The occurrence and effectiveness of hypersensitive reaction against galling herbivores across host taxa

1. Hypersensitive reaction is an important type of induced defence by which the plant elicits a defence response to pathogens and insects. Hypersensitive reaction has been argued to be the most common plant resistance mechanism against insect herbivores that have intimate associations with their host plants. 2. The work reported here attempted to establish how important and widespread hypersensitive reaction might be against gall‐forming species across host taxa. 3. Hypersensitive reaction was the most important mortality factor against gall formation across host plant taxa in seven out of eight cases. 4. The number of insect galls correlated with the size of the leaves but module (leaf) size was a weak factor influencing the incidence of plant hypersensitive reaction to galling. 5. Insect galls and hypersensitive reactions occurred in genetically distant as well as geographically widespread host plant taxa.     

The applicability of the plant vigor and resource regulation hypotheses in explaining Epiblema gall moth–Parthenium weed interactions

A basic question in insect–plant interactions is whether the insects respond to, or regulate plant traits, or a complex mixture of the two. The relative importance of the directions of the influence in insect–plant interactions has therefore been articulated through both the plant vigor hypothesis (PVH) and the resource regulation hypothesis (RRH). This study tested the applicability of these hypotheses in explaining the interactions between Parthenium hysterophorus L. (Asteraceae) and its stem‐galling moth, Epiblema strenuana Walker (Lepidoptera: Tortricidae). Parthenium plants exposed to galling were sampled at three sites in north Queensland, Australia, over a 2‐year period, and the relationship between gall abundance and plant vigor (plant height, biomass, flowers per plant, and branches per plant) was studied. To test the predictions of PVH and RRH, the vigor of parthenium plants protected from galling using insecticides was compared to galled plants and plants that escaped from galling. The vigor of ungalled plants was less than the vigor of galled plants. The higher plant vigor in galled plants was not due to galling, as was evident from insecticide exclusion trials. The insect seemed to preferentially gall the more vigorous plants. These findings support the predictions of the PVH and are contrary to those of RRH. Since gall abundance is linked to plant vigor, galling may have only a limited impact on the vigor of parthenium. This has implications for weed biological control. If the objective of biological control is to regulate the population of a plant by a galling insect, a preference for more vigorous plants by the insect is likely to limit its ability to regulate plant populations. This may explain the paucity of successes against biocontrol of annual weeds using gall insects.     

Phenotypic plasticity and similarity among gall morphotypes on a superhost,Baccharis reticularia (Asteraceae)

Understanding factors that modulate plant development is still a challenging task in plant biology. Although research has highlighted the role of abiotic and biotic factors in determining final plant structure, we know little of how these factors combine to produce specific developmental patterns. Here, we studied patterns of cell and tissue organisation in galled and non‐galled organs of Baccharis reticularia, a Neotropical shrub that hosts over ten species of galling insects. We employed qualitative and quantitative approaches to understand patterns of growth and differentiation in its four most abundant gall morphotypes. We compared two leaf galls induced by sap‐sucking Hemiptera and stem galls induced by a Lepidopteran and a Dipteran, Cecidomyiidae. The hypotheses tested were: (i) the more complex the galls, the more distinct they are from their non‐galled host; (ii) galls induced on less plastic host organs, e.g. stems, develop under more morphogenetic constraints and, therefore, should be more similar among themselves than galls induced on more plastic organs. We also evaluated the plant sex preference of gall‐inducing insects for oviposition. Simple galls were qualitative and quantitatively more similar to non‐galled organs than complex galls, thereby supporting the first hypothesis. Unexpectedly, stem galls had more similarities between them than to their host organ, hence only partially supporting the second hypothesis. Similarity among stem galls may be caused by the restrictive pattern of host stems. The opposite trend was observed for host leaves, which generate either similar or distinct gall morphotypes due to their higher phenotypic plasticity. The Relative Distance of Plasticity Index for non‐galled stems and stem galls ranged from 0.02 to 0.42. Our results strongly suggest that both tissue plasticity and gall inducer identity interact to determine plant developmental patterns, and therefore, final gall structure.     

Cytological and histochemical gradients on two <Emphasis Type="BoldItalic">Copaifera langsdorffii</Emphasis> Desf. (Fabaceae)—Cecidomyiidae gall systems

Previous ultrastructural and histochemical analysis proposed patterns in the accumulation of substances in galls of Diptera: Cecidomyiidae in some plant species of the temperate region. Similar analyses were done to verify the conservativeness of these patterns in the Neotropical region, where a great number of species of Cecidomyiidae is responsible for a wide diversity of morphotypes. Two gall morphotypes induced by Cecidomyiidae in a unique host plant, Copaifera langsdorffii, were studied. The gradients of carbohydrates and the activity of invertases and acid phosphatases were similar, but the cytological gradients and distribution of proteins evidenced that the sites of the induction as well as the amount of neoformed tissues may be peculiar to each gall system. The production of lipids just in the secretory cavities either in the non-galled or galled tissues indicated a potentiality of the host plant which could not be manipulated by the galling insects. Further, the absence of nucleus in the nutritive tissue, an exclusive feature of the horn-shaped galls, indicates cell death attributed to the feeding habit of the galling herbivore.     

Leaf gall polymorphism and molecular phylogeny of a new Bruggmanniella species (Diptera: Cecidomyiidae: Asphondyliini) associated with Litsea acuminata (Lauraceae) in Taiwan,with ecological comparisons and a species description

Two types of cecidomyiid leaf galls, cup‐shaped and umbrella‐shaped, occur on Litsea acuminata (Lauraceae) in Taiwan. Based on the concept of gall shapes as “extended phenotypes” of gall inducers, these two types could be induced by different gall midge species. However, galls with intermediate shapes between the two types were recently discovered, which implies that possible genetic exchanges occur between the gall inducers of both types. To clarify the taxonomic status of gall midges responsible for the two types of galls on L. acuminata, we undertook taxonomic, molecular phylogenetic and ecological studies. Our findings show that the two gall types are induced by the same Bruggmanniella species and the species is new to science. We describe the species forming this range of galls as Bruggmanniella litseae sp. n. , and compare their geographical distribution, galling position and morphometry. Based on our results, a possible evolutionary scenario of B. litseae sp. n. is discussed.     

Nutrition as a facilitator of host‐race formation: the shift of a stem‐boring beetle to a gall host

1. The importance of host‐race formation to herbivorous insect diversity depends on the likelihood that successful populations can be established on a new plant host. A previously unexplored ecological aid to success on a novel host is better nutritional quality. The role of nutrition was examined in the shift of the stem‐boring beetle Mordellistena convicta to fly‐induced galls on goldenrod and the establishment there of a genetically distinct gall host race. 2. First, larvae of the host race inhabiting stems of Solidago gigantea were transplanted into stems and galls of greenhouse‐grown S. gigantea plants. At the end of larval development, the mean mass of larvae transplanted to galls was significantly greater than the mass of larvae transplanted to stems, indicating a likely nutritional benefit during the shift. This advantage was slightly but significantly diminished when the gall‐inducing fly feeding at the centre of the gall died early in the season. Additionally, there was a suggestion of a trade‐off in the increased mortality of smaller beetle larvae transplanted into galls. 3. In a companion experiment, S. gigantea gall‐race beetle larvae were likewise transplanted to S. gigantea stems and galls. Besides the expected greater mass in galls, the larvae also exhibited adaptations to the gall nutritional environment: larger inherent size, altered tunnelling behaviour, and no diminution of mass pursuant to gall‐inducer mortality. 4. In a third line of inquiry, chemical analyses of field‐collected S. gigantea plants revealed higher levels of mineral elements important to insect nutrition in galls as compared with stems.     

Spatiotemporal fluctuations in natural selection acting on the gall‐parasitic aphid Tetraneura sorini

The measurement of the selection gradient is crucial for understanding the magnitude of selection acting directly on a trait and predicting the evolutionary trajectory of that trait. This study evaluated the selection gradient acting on the morphology of the gall‐parasitic aphid Tetraneura sorini during the galling process and compared the strength among populations. Gall formers (first instars) frequently fight with conspecifics or heterospecifics for usurping incipient galls using their well‐developed hind legs. First instars that successfully acquired galls were found within galls, whereas those that failed were found dead on leaf surfaces. Selection gradients were estimated using logistic stepwise regression and partial least square (PLS) regression. Calculated selection differentials indicated that first instars that secured galls were larger in body size than failed individuals through all populations. However, selection gradients on weapon traits varied largely among populations or among years in the same population. We confirmed microevolutionary changes in the relationship between traits, which accorded with the expectation from changes in the selection gradients. When gall formers were transferred onto developing buds individually, individuals that successfully induced galls had smaller body size than failed individuals. Available evidence suggests that the selection gradient on body size becomes higher with an increasing proportion of T. sorini in the Tetraneura species community. Thus, we concluded that more intense fighting with conspecifics leads to stronger selective pressure on body size, but that selective pressure for each trait is variable depending on differences in the tactics and species composition among populations.     

Vigour of a dioecious shrub and attack by a galling herbivore

1. The pattern of attack by the leaf‐galling insect Neopelma baccharidis (Homoptera: Psyllidae) was studied in three populations of the dioecious shrub Baccharis dracunculifolia (Asteraceae) in south‐eastern Brazil. The plant vigour hypothesis, which predicts higher rates of attack and increased herbivore performance on the longest plant shoots, was tested. This work also provides further information for the study of differential herbivory in dioecious plants. 2. In total, 9200 shoots were collected randomly from 46 male and 47 female plants belonging to the three populations. Shoot length, number of leaves per shoot, rate of galling, and survival of psyllids did not differ between male and female plants. Another population on the Campus of the Federal University of Minas Gerais was used only to determine the pattern of shoot growth. 3. The hypothesis of sex‐mediated herbivory was not corroborated in this study. 4. The frequency of galling increased with increasing shoot length, as predicted by the plant vigour hypothesis. Nevertheless, the number of oviposition sites (leaf buds) increased with shoot length. 5. The performance of the galling herbivore was not related to shoot length in the plant populations studied. 6. In conclusion, Neopelma baccharidis did not select shoots based on length only.     

Testing the nutrition hypothesis for the adaptive nature of insect galls: does a non‐adapted herbivore perform better in galls?

Abstract.  1. The nutrition hypothesis for the adaptive nature of galls states that gall-inducing insects control the nutrient levels in galls to their own benefit. Although the nutrition hypothesis is widely accepted, there have been few empirical tests of this idea.
2. A novel method is presented for testing the nutrition hypothesis that links manipulation of gall nutrient levels by the gall inducer to herbivore performance. The effects of adaptation and nutritional advantage are separated by using a herbivore that is adapted to a host plant susceptible to galling but one which never enters the gall environment.
3.  Hellinsia glenni (Cashatt), a plume moth (Pterophoridae) and one of its host plants provide an excellent system for testing the nutrition hypothesis because H. glenni larvae feed internally on the relatively nutrient-poor stems of a goldenrod, Solidago gigantea , but do not venture into the nutrient-rich galls induced on that plant by a tephritid fly, Eurosta solidaginis . The nutrition hypothesis was tested by transplanting early-instar H. glenni larvae into galls and stems of S. gigantea to determine if the larvae transplanted to galls would perform better compared with those larvae transplanted to stems.
4. The results support the nutrition hypothesis for the adaptive nature of galls. Hellinsia glenni achieved greater final mass in the gall environment compared with the final mass larvae achieved in the stem environment. There was also evidence that the quality of gall tissue is controlled by the gall inducer, which has not been previously demonstrated for mature E. solidaginis galls.     

Post‐gall induction performance of Adelges Abietis (L.) (Homoptera: Adelgidae) is influenced by clone,shoot length,and density of colonising gallicolae

1. We evaluated the effect of clone (one susceptible and one resistant clone), shoot length, crown level, and gallicola density on post‐gall induction performance of Adelges abietis. Galls that had been successfully induced by one fundatrix on a range of shoot sizes were selected, and the number of gallicolae that could colonise the gall was manipulated. 2. Post‐induction gall development success was inversely related to shoot length and was higher on the susceptible clone than on the resistant clone. As gallicola density did not influence the proportion of galls that successfully completed development, reduced post‐induction gall development on large shoots was not likely to be result of an insufficient stimulus from gallicolae. 3. Clone was the only factor that significantly influenced gall volume and galls were larger on the susceptible clone than on the resistant clone. As gall volume did not increase when more gallicolae attempted to colonise a gall, competition within a gall increased. Gallicola survival was inversely related to the number of colonising gallicolae. Our results suggest that gall size may be limiting at natural densities. 4. Previous studies report positive relationships between gall induction success and fundatrix density, and between gall size and fundatrix density. As each fundatrix produces one egg mass of gallicolae, this study suggests that there may be a trade‐off between the successful induction of a large gall and subsequent survival of gallicolae. 5. In the present study, clone influenced all measures of post‐gall induction performance. Performance was always higher on the susceptible than on the resistant clone.     

The protein content of tissues in cynipid galls (Hymenoptera: Cynipidae): Similarities between cynipid galls and seeds

Cynipid galls are examples of induced plant development, where the gall inducer is in control of cell differentiation and morphogenesis of a new plant organ. This study concentrates on the tissues of the larval chamber common to all cynipid galls. The protein content of the inner gall tissue was compared to that of non‐gall plant tissues. We investigated three oak and two rose galls and their respective host plants. Total protein signatures of inner gall tissues were different from those of non‐gall plant tissues, and among the five galls. N‐terminal sequences were obtained for two abundant proteins from the inner gall tissues of D. spinosa and A. quercuscalicis, which were common to all galls, at 62 and 43 kDa. Database queries suggest the 62 kDa protein to be homologous to a protein disulphide isomerase (PDI), and the 43 kDa protein to be homologous to NAD‐dependent formate dehydrogenase (FDH). A naturally biotinylated protein was detected at 33 kDa during Western analyses with streptavidin. Western analyses revealed the presence of the biotinylated protein and PDI in the inner gall tissues of all five galls, while FDH was only detected in A. quercuscalicis and A. fecundator. PDI was also common to all non‐gall tissues, while FDH was not detected in non‐gall tissues, and the biotinylated protein was only detected in seeds. The proteins identified in the inner gall tissue suggest that (a) inner gall tissues in some galls are under respiratory stress, and (b) cynipid gall formation might involve the ectopic expression of seed‐specific proteins.