Fossil oak galls preserve ancient multitrophic interactions

Trace fossils of insect feeding have contributed substantially to our understanding of the evolution of insect-plant interactions. The most complex phenotypes of herbivory are galls, whose diagnostic morphologies often allow the identification of the gall inducer. Although fossil insect-induced galls over 300Myr old are known, most are two-dimensional impressions lacking adequate morphological detail either for the precise identification of the causer or for detection of the communities of specialist parasitoids and inquilines inhabiting modern plant galls. Here, we describe the first evidence for such multitrophic associations in Pleistocene fossil galls from the Eemian interglacial (130000-115000 years ago) of The Netherlands. The exceptionally well-preserved fossils can be attributed to extant species of Andricus gallwasps (Hymenoptera: Cynipidae) galling oaks (Quercus), and provide the first fossil evidence of gall attack by herbivorous inquiline gallwasps. Furthermore, phylogenetic placement of one fossil in a lineage showing obligate host plant alternation implies the presence of a second oak species, Quercus cerris, currently unknown from Eemian fossils in northwestern Europe. This contrasts with the southern European native range of Q. cerris in the current interglacial and suggests that gallwasp invasions following human planting of Q. cerris in northern Europe may represent a return to preglacial distribution limits.     

Stem galls affect oak foliage with potential consequences for herbivory

Abstract.   1. On two dates, foliar characteristics of pin oak, Quercus palustris , infested with stem galls caused by the horned oak gall, Callirhytis cornigera , were investigated, and the consequences for subsequent herbivory assessed.
2. Second-instar caterpillars of the gypsy moth, Lymantria dispar , preferred foliage from ungalled trees.
3. Ungalled trees broke bud earlier than their galled counterparts.
4. Galled trees produced denser leaves with higher nitrogen and tannin concentrations, but foliar carbohydrates did not differ among galled and ungalled trees.
5. Concentrations of foliar carbohydrates in both galled and ungalled trees increased uniformly between the two assay dates. Nitrogen concentrations were greater in leaves from galled trees, and decreased uniformly in galled and ungalled trees over time. Foliar tannins were also greater in foliage from galled trees early in the season; however, foliar tannins declined seasonally in galled tissue so that by the second assay date there was no difference in tannin concentrations between galled and ungalled foliage.
6. In spite of differences in foliar characteristics, performance of older, fourth instar gypsy moth caterpillars did not differ between galled and ungalled trees.     

Discovery of an oak gall wasp (Hymenoptera: Cynipidae) inducing galls on deciduous oak trees in India

We report for the first time the occurrence of an oak gall wasp Andricus mukaigawae (Mukaigawa) (Hymenoptera: Cynipidae) on the deciduous oak Quercus griffithii Hook. F & Thomson ex Miq. in India. Andricus mukaigawae is the only cynipid species that has been observed to induce galls on deciduous oak species in India to date. In addition, this is the first record of a gall wasp species with a distribution extending all the way from the eastern Palearctic region to the Indian subcontinent, suggesting the existence of a close relationship between cynipid faunas on deciduous oak trees in the two regions.     

Biomass,production and nutrient distribution of a natural oak forest in central Korea

Biomass, production, and nutrient distribution of a pure Quercus variabilis Bl. stand (stand 1) and two mixed Q. variabilis–Q. mongolica Fisch. stands (stand 2 and 3) were investigated in central Korea. Stand 1 naturally occurred on a site with a southern aspect while stand 2 and stand 3 occurred on sites with a northern aspect. Total (overstory+understory vegetation) biomass (tha^-1) and annual production (tha^–1year^–1) were 137.8 and 11.1 for stand 1, 216.2 and 16.6 for stand 2, and 253.3 and 19.7 for stand 3. Nutrient contents (kgha^–1) in the vegetation were distributed as follows: K, 478–860; N, 471–839; Ca, 428–791; Mg, 72–125; Na, 77–141; and P, 37–71, and were greatest in stand 3 followed by stand 2, and stand 1. Stand density influenced the differences in biomass, annual production and nutrient contents in the vegetation. Forest floor dry mass and N content (kgha^–1) were 13400 and 169 for stand 1, 10400 and 133 for stand 2, and 11200 and 127 for stand 3. Total amounts of N, P and Na in the ecosystem were greatest in the upper 40cm of mineral soil followed by the vegetation and forest floor. However, the vegetation contained a greater amount of K than the mineral soil. It appeared that microenvironments, such as, aspect influenced the distribution of natural oak species within a relatively small area and resulted in differences in biomass, production and nutrient distribution among the stands.     

虫瘿多样性及其与寄主植物和环境间关系

虫瘿是自然界极常见的生物现象,凝聚着昆虫与植物间显著、复杂而密切的协同关系。本文主要阐述了致瘿昆虫的主要类群及其在植物上的致瘿部位、虫瘿外部形态、虫瘿发育过程、虫瘿内部结构、虫瘿寄主植物多样性以及虫瘿空间分布规律等,探讨了致瘿昆虫和寄主植物间相互关系,以及影响虫瘿空间分布的环境因素等。最后对目前虫瘿生物学存在的问题及以后的研究方向进行了讨论,以期为有害虫瘿的控制和有益虫瘿的开发与利用,以及致瘿昆虫与寄主植物间协同演化关系、致瘿昆虫的致瘿机理等研究奠定一定的理论基础。     

Genetic transformation of selected mature cork oak (Quercus suber L.) trees

A transformation system for selected mature cork oak (Quercus suber L.) trees using Agrobacterium tumefaciens has been established. Embryos obtained from recurrent proliferating embryogenic masses were inoculated with A. tumefaciens strains EHA105, LBA4404 or AGL1 harbouring the plasmid pBINUbiGUSint [carrying the neomycin phosphotransferase II (nptII) and -glucuronidase (uidA) genes]. The highest transformation efficiency (4%) was obtained when freshly isolated explants were inoculated with A. tumefaciens strain AGL1. Evidence of stable transgene integration was obtained by PCR for the nptII and uidA genes, Southern blotting and expression of the uidA gene. The transgenic embryos were germinated and successfully transferred to soil.Abbreviations BA N⁶-Benzyladenine - GUS -Glucuronidase - MSSH Expression-proliferation medium - NAA -Naphthaleneacetic acid - nptII Neomycin phosphotransferase gene - uidA -Glucuronidase gene     

Tournament ABC analysis of the western Palaearctic population history of an oak gall wasp,Synergus umbraculus

Approximate Bayesian computation (ABC) is a powerful and widely used approach in inference of population history. However, the computational effort required to discriminate among alternative historical scenarios often limits the set that is compared to those considered more likely a priori. While often justifiable, this approach will fail to consider unexpected but well‐supported population histories. We used a hierarchical tournament approach, in which subsets of scenarios are compared in a first round of ABC analyses and the winners are compared in a second analysis, to reconstruct the population history of an oak gall wasp, Synergus umbraculus (Hymenoptera, Cynipidae) across the Western Palaearctic. We used 4,233 bp of sequence data across seven loci to explore the relationships between four putative Pleistocene refuge populations in Iberia, Italy, the Balkans and Western Asia. We compared support for 148 alternative scenarios in eight pools, each pool comprising all possible rearrangements of four populations over a given topology of relationships, with or without founding of one population by admixture and with or without an unsampled “ghost” population. We found very little support for the directional “out of the east” scenario previously inferred for other gall wasp community members. Instead, the best‐supported models identified Iberia as the first‐regional population to diverge from the others in the late Pleistocene, followed by divergence between the Balkans and Western Asia, and founding of the Italian population through late Pleistocene admixture from Iberia and the Balkans. We compare these results with what is known for other members of the oak gall community, and consider the strengths and weaknesses of using a tournament approach to explore phylogeographic model space.     

Quercus tuitensis (Fagaceae, Quercus sect. Lobatae), a new deciduous oak from western Jalisco, Mexico

Quercus tuitensis, a deciduous red oak known only from the Sierra El Tuito on the Pacific slopes of western Jalisco, Mexico, is described, illustrated, and compared toQ. praineana Trel. In addition,Q. aequivenulosa andQ. coffeaecolor are reaffirmed as synonyms ofQ. praineana.     

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.     

Morphogenesis of insect-induced plant galls: facts and questions

Insect-induced galls (‘galls’ hereafter) represent highly regulated growth manifestations on plants. They present unique geometrical forms, which are, usually, unknown in the normal plant system. Galls are the best examples for modified natural structures that arise solely because of messages from an alien organism - the insect. Galls develop as an extension of the host-plant phenotype. But how the physiological networks and signal-activated subsystems work in coordination in expressing galls that serve the nutritional and shelter needs of the inducing insect are unclear. In galls and bacteria-induced tumors, the basic developmental events are essentially similar. However, tightly regulated specific differentiation processes occur in galls, making them different from tumors. Moreover variations in differentiation patterns occur in galls induced by insects of different taxonomic groups. While providing an overview of the control of shape and structure in galls, this article identifies the unanswered questions in gall morphogenesis.By analyzing the recognizable steps in gall morphogenesis, viz., gall initiation, stimulus recognition in host plants, signal transduction in host plants, growth of galls, and qualitative differentiation in galls, I have indicated that the insect saliva flushed on the wounded plant site alters the subcellular environment of cells and thus places it in a state of chemical shock. This shock induces osmotic changes, which establishes the first recognizable stage in gall induction. To repair the wound and neutralize the osmotic-change induced stress, the plant responds by establishing from one to a few metaplasied cell(s). Localized metabolic changes spread, from these cells, not throughout the involved plant organ, but in a limited manner around the immediate site of insect occurrence. When the shock is of low intensity, the plant responds with the development of one or more metaplasied cell(s) and gall development starts; when the shock factor is of high intensity, the cells under the insect action die, rejecting the inducing insect, defending plant tissue. These changes dictate the new morphogenetic events. Insects feed on gall tissue continuously for a specific period (synchronizing with their life history) and therefore, the osmotic-change related stress prevails for that span of time, which in turn triggers a sequence of plant-mediated changes including synthesis of growth promotors. Osmotic stress affects electrical properties of the plasma membrane and impacts on IAA activity, which in turn, alters H⁺-transport systems. During the physical action of insect feeding, the host-cell wall breaks down, and the degenerated wall materials act as elicitors.Using galls (e.g., ‘cecidial shoots’ on leaves, modified vegetative buds) induced on species of south and south-east Asian Dipterocarpaceae by different Beesoniidae (Coccoidea) as model complexity in gall morphogenesis is discussed. Manipulatory experimental studies done on the regeneration of epiphyllous buds on Pteridium, Begonia, and a Helianthus hybrid indicate that insect-induced neoplasmic shoots that arise on the leaves of tropical Dipterocarpaceae fall into the morphogenetic regulation of leaf, yet maintaining their freedom of differentiation. Even though a gall is a part of the plant - a multicellular organism made of the same genetic material - organismal development generates a range of cell types with dictated functions fitting into of Waddington's epigenetic-landscape model. As of today, our knowledge stops here.Plants as living systems display different strategies to mitigate and neutralize stress. Although these strategies exist in their genetic constitution, they are mediated by complex molecular interactions. Plants have a flexible short-term strategy to respond to stress; organisms that can modify gene expression reversibly have an advantage in evolutionary terms, since they can avoid rearrangements and species diversification. Mechanisms of DNA methylation and histone modifications possibly regulate inheritance of stress ‘memories’. Inherited genetic traits also play a role in gall morphogenesis, followed by roles played by correlating morphogenetic factors. An articulated reconstruction of the developmental process commencing from either one or a group of metaplasied cells that gets transmitted through subsequent growth promoter-mediated cell expansion, until the commitment of the metaplastic cell and those in its neighbourhood enabling the start of ‘novel’ cell-cycle patterns, cell multiplication, programmed differentiation, and control is needed to explain symmetry - a morphogenetic phenomenon that makes the insect-induced galls distinct from the bacteria-induced tumors.     

Effect of the Herbicide Atrazine on the Bean Leaf Lipids

Eight-day-old bean plants, grown in a nutrient solution, were sprayed with 10⁻⁵, 10⁻⁴, 10⁻³, and 10⁻² M atrazine. The lipid changes in primary and trifoliate leaves were studied 6 d after the herbicide application. The atrazine treatment inhibited the growth of the trifoliate leaves, and decreased photosynthetic and transpiration rates, the stomatal conductance, and the total lipid content. Atrazine treatment increased 16:0 and 18:3 acids and decreased trans-3-hexadecenoic and 18:2 acids in the phospholipids. The herbicide also increased 16:0 and 18:1 acids in glycolipids and decreased 18:3 acid in monogalactosyl diacylglycerols and digalactosyl diacylglycerols. In most cases the marked changes in fatty acid composition of the main lipid classes were observed at 10⁻⁴ and 10⁻³ M atrazine. This revised version was published online in June 2006 with corrections to the Cover Date.     

松针鞘瘿蚊在黑松冠层的空间分布特征与脱瘿节律研究

为掌握松针鞘瘿蚊Thecodiplosis japonensis幼虫在黑松冠层的分布特征和脱瘿节律,本文采用标准株调查法,调查了松针鞘瘿蚊幼虫在冠层的不同方位的虫口密度.采用陷阱法,调查了不同时期越冬幼虫的下树数量.结果表明,在黑松树冠的顶梢、上层、中层、下层,松针受害率分别为67.42％、68.59％、52.22％和...