Publications

molecular evidence against phylogenetically distinct host races of the pea aphid (acyrthosiphon pisum).	pea aphid (acyrthosiphon pisum) clones have been shown to be adapted to particular host plant species but it is unknown whether there are host races. a 1101 base pair region of the mitochondrial cytochrome oxidase i gene (coi) was sequenced for 21 pea aphid clones that had been collected from different host plants in canada and the u.s.a. only five closely related mitochondrial haplotypes were found. a maximum likelihood phylogeny was estimated for these five haplotypes and four related aphid sp ...	1998	9924789
the developmental strategy of an idiobiont ectoparasitoid, dendrocerus carpenteri : influence of variations in host quality on offspring growth and fitness.	dendrocerus carpenteri (curtis) (hymenoptera: megaspilidae) is a solitary hyperparasitoid, which attacks prepupal and pupal stages of hymenopteran parasitoids inside mummified aphids. the larva feeds externally on the host, which is envenomed by the female at oviposition. to evaluate the influence of variations in host quality on the growth, development and fitness of d. carpenteri, we varied the size and developmental stage of the primary parasitoid host (aphidius ervi haliday), which was reare ...	1998	28307914
interactions between an introduced and indigenous coccinellid species at different prey densities.	coccinella septempunctata l. (coleoptera: coccinellidae), a palearctic coccinellid, has established and rapidly spread throughout the united states. this quantitative examination of larval interactions between c. septempunctata and coleomegilla maculata (degeer) (coleoptera: coccinellidae), a nearctic coccinellid, was conducted under controlled prey densities. larvae of both coccinellid species are affected by a limited diet [one pea aphid per day acyrthosiphon pisum (harris) (homoptera: aphidid ...	1998	28308499
the role of vision and color in the close proximity foraging behavior of four coccinellid species.	the role of vision and color in close-proximity foraging behavior was investigated for four species of lady beetles: coccinella septempunctata, hippodamia convergens, harmonia axyridis, and coleomegilla maculata. the effect of light level and color cues on consumption rates varied among the four predator species. the consumption rates of these predators on the pea aphid acyrthosiphon pisum (harris) was measured under light and dark conditions. c. septempunctata,h. convergens, and ha. axyridis co ...	1998	28308464
interspecific variation in the escape responses of aphids: effect on risk of predation from foliar-foraging and ground-foraging predators.	a series of laboratory experiments was conducted to determine the effect of interspecific differences on prey defensive behavior on the susceptibility of two aphid species (acyrthosiphon pisum and a. kondoi) to a ground-foraging predator, harpalus pennsylvanicus, and a foliar-foraging predator, coccinella septempunctata. these organisms are representative of a biologically and economically important predator/prey system in alfalfa. the primary defensive behavior of both aphid species toward c. s ...	1998	28308458
implications of predator foraging on aphid pathogen dynamics.	the foraging behavior of starved and nonstarved second and fourth instar coccinella septempunctata larvae on dead acyrthosiphon pisum aphids, either infected with the entomopathogenic fungus erynia neoaphidis (sporulating) or uninfected, was examined. larvae searched for longer and fed less when presented with infected rather than uninfected a. pisum. although no sporulating infected aphids were completely consumed, both adult and larval ladybirds can still be considered as intraguild predators. ...	1998	9538028
host regulation effects of ovary fluid and venom of aphidius ervi (hymenoptera: braconidae).	the host regulation effects of venom and ovary fluid of the endophagous braconid aphidius ervi haliday on the pea aphid, acyrthosiphon pisum (harris), have been studied. extracts of ovaries and of venom glands were injected into nonparasitized 4th instar pea aphids, both separately and mixed. aphids treated with parasitoid material died as 4th instars, often showing developmental arrest. in contrast, control aphids that received an injection of pringle's saline solution regularly moulted to the ...	1998	12769873
host cell allometry and regulation of the symbiosis between pea aphids, acyrthosiphon pisum, and bacteria, buchnera.	the symbiotic bacteria buchnera in aphids are borne in cells, called bacteriocytes, in the insect haemocoel. the number and median volume of bacteriocytes in pre-reproductive adult insects varied significantly among 14 parthenogenetic clones of the pea aphid acyrthosiphon pisum. after logarithmic transformation of the data, the relationship of both number and median volume of bacteriocytes with aphid weight for the clones could be described by common regression lines with slopes significantly gr ...	1998	12769945
method to immobilize the aphid-pathogenic fungus erynia neoaphidis in an alginate matrix for biocontrol	erynia neoaphidis is an important fungal pathogen of aphid pests worldwide. there have been few reported attempts to formulate this natural agent for use in biocontrol. in the current study, factors involved in the immobilization of e. neoaphidis hyphae in an alginate matrix were investigated. hyphae of two isolates cultured in liquid medium were 220 to 620 &mgr;m in length and 7 to 19 &mgr;m in diameter with a 74 to 83% cytoplasmic content. the optimal concentration of low-viscosity sodium algi ...	1998	9797274
physical and genetic map of the genome of buchnera, the primary endosymbiont of the pea aphid acyrthosiphon pisum.	the genome of buchnera, an endosymbiotic bacterium of the pea aphid acyrthosiphon pisum, was characterized by pulse-field gel electrophoresis (pfge) as a circular dna molecule of 657 kb. the enzymes i-ceui, cpoi, apai, smai, naei, sacii, mlui, fspi, and nrui were used to cleave the dna of buchnera into fragments of suitable size for pfge analysis. a physical map of the buchnera genome, including restriction fragments from seven of these enzymes, was constructed using double cutting, partial dige ...	1999	9929382
the role of rdna genes in x chromosome association in the aphid acyrthosiphon pisum.	silver staining of mitotic metaphases of the aphid a. pisum reveals the presence of argentophilic bridges connecting the two x chromosomes. the presence of nucleolar material connecting sex chromosomes seems to be quite a common phenomenon in organisms belonging to very different phyla, and suggests a role of nucleolar proteins in chromosome association and disjunction. in somatic cells of a. pisum, bridges connecting x chromosomes are detectable not only after silver staining but also after cma ...	1999	10382287
low genetic diversity among pea aphid (acyrthosiphon pisum) biotypes of different plant affiliation.	genetic diversity in the pea aphid acyrthosiphon pisum was investigated by a restriction fragment length polymorphism (rflp) analysis of three maternally inherited genomes (mitochondrial dna and plasmids of the symbiotic bacteria buchnera). twenty-nine parthenogenetic clones of three a. pisum biotypes, defined by their capacity to use the legume crops pea, alfalfa and red clover, respectively, were analysed, and a total of 67 restriction sites was scored. no restriction site variation in the mit ...	1999	10383681
effects of fungal infection on the alarm response of pea aphids	pea aphids (acyrthosiphon pisum, homoptera: aphididae) infected with the fungal pathogen erynia neoaphidis (zygomycetes: entomophthorales) were less sensitive to the aphid alarm pheromone (e)-beta-farnesene than uninfected aphids. approximately 83% of the healthy aphids and 45% of the infected aphids (2 and 3 days post-inoculation) responded to the alarm pheromone. the percentage of nonresponding aphids increased as the disease progressed. when squeezed (simulated attack) healthy aphids and aphi ...	1999	10388549
isolation and characterization of apse-1, a bacteriophage infecting the secondary endosymbiont of acyrthosiphon pisum.	a bacteriophage infecting the secondary endosymbiont of the pea aphid acyrthosiphon pisum was isolated and characterized. the phage was tentatively named bacteriophage apse-1, for bacteriophage 1 of the a. pisum secondary endosymbiont. the apse-1 phage particles morphologically resembled those of species of the podoviridae. the complete nucleotide sequence of the bacteriophage apse-1 genome was elucidated, and its genomic organization was deduced. the genome consists of a circularly permuted and ...	1999	10489345
faba bean necrotic yellows virus (genus nanovirus) requires a helper factor for its aphid transmission.	purified faba bean necrotic yellows virus (fbnyv; genus nanovirus) alone is not transmissible by its aphid vector, acyrthosiphon pisum, regardless of whether it is acquired from artificial diets or directly microinjected into the aphid's hemocoel. the purified virus contains all of the genetic information required for its infection cycle as it readily replicated in cowpea protoplasts and systemically infected vicia faba seedlings that were biolistically inoculated using gold particles coated wit ...	1999	10489354
aphids, predators and parasitoids.	a number of studies have demonstrated the role of herbivore-induced release of plant volatiles in mediating foraging behaviour of aphid parasitoids, particularly with the parasitoid aphidius ervi, its aphid host acyrthosiphon pisum and the aphid food plant vicia faba. these studies have shown that feeding by the aphid alters the composition of volatiles released by the plant and that these compounds act as synomones for the foraging parasitoid. of particular interest is the species-specificity o ...	1999	10549548
variability and parasitoid foraging efficiency: a case study of pea aphids and aphidius ervi.	when a parasitoid is searching for hosts, not all hosts are equally likely to be attacked. this variability in attack probability may affect the parasitoid functional response. using a collection of experiments, we quantified the functional response of aphidius ervi (hymenoptera: braconidae), an insect parasitoid of the pea aphid acyrthosiphon pisum (homoptera: aphididae). we measured variability in the number of hosts attacked by a foraging parasitoid both among plants and within plants. at the ...	1999	10600611
acetone preservation: a practical technique for molecular analysis.	in attempts to establish a convenient and reliable method for field collection and archival preservation of insects and their endosymbiotic microorganisms for molecular analysis, acetone, ethanol, and other organic solvents were tested for dna preservability of the pea aphid acyrthosiphon pisum and its intracellular symbiotic bacterium buchnera sp. after 6 months' storage, not only the band of high-molecular-size dna but also the bands of rrna were well preserved in acetone, ethanol, 2-propanol, ...	1999	10620236
provision of riboflavin to the host aphid, acyrthosiphon pisum, by endosymbiotic bacteria, buchnera.	differential cdna display and quantitative rt-pcr suggested that the riboflavin synthase complex of the aphid endosymbiont, buchnera, is active only when the symbiotic system is maintained and well organized in young hosts. since this finding suggested the provision of riboflavin by buchnera, we examined the effect of dietary riboflavin on the performance of symbiotic and aposymbiotic aphids using chemically-defined diets. our results indicate: (1) dietary riboflavin is slightly detrimental to y ...	1999	12770389
identification, characterization, and relatedness of luteovirus isolates from forage legumes.	abstract virus isolates from forage legumes collected from eight different states were identified as luteoviruses closely related to soybean dwarf luteovirus dwarfing (sbdv-d) and yellowing (sbdv-y) described in japan. all isolates produced reddened leaf margins in subterranean clover and were transmitted in a persistent manner by acrythosiphon pisum, but not by aulacorthum solani. specific monoclonal antibodies raised against sbdv-y were differentially reactive with endemic isolates. immunoblot ...	1999	18944749
fate of dietary sucrose and neosynthesis of amino acids in the pea aphid, acyrthosiphon pisum, reared on different diets	the fate of sucrose, the major nutrient of an aphid's natural food, was explored by radiolabeling in the pea aphid acyrthosiphon pisum. to investigate the influence of nitrogen quality of food on amino acid neosynthesis, pea aphids were reared on two artificial diets differing in their amino acid composition. the first (diet a) had an equilibrated amino acid balance, similar to that derived from analysis of aphid carcass, and the other (diet b) had an unbalanced amino acid composition similar to ...	1999	10482723
importance of population structure at the time of toxicant exposure.	populations in nature often consist of a mixture of stages and ages, yet toxicological studies even demographic studies, usually evaluate one starting life stage. in this study it was asked whether the starting age/stage structure of a population at the time of initial pesticide exposure influenced the impact that pesticides have on population growth rates. this question was answered by exposing differently structured populations of two terrestrial arthropod species, the two-spotted spider mite, ...	1999	10090817
essential versus alternative foods of insect predators: benefits of a mixed diet.	although many predatory insects appear to be opportunistic generalists in their selection of prey, only a subset of prey species may in fact serve as "essential foods" capable of supporting immature growth and adult reproduction. it has been suggested that other, "alternative foods" serve only to maintain the predator when essential foods are not available, but little research has evaluated the significance of a mixed diet of essential and alternative foods for predator growth or reproduction. h ...	1999	28307878
evolution of an aphid-parasitoid interaction: variation in resistance to parasitism among aphid populations specialized on different plants.	the evolution of associations between herbivorous insects and their parasitoids is likely to be influenced by the relationship between the herbivore and its host plants. if populations of specialized herbivorous insects are structured by their host plants such that populations on different hosts are genetically differentiated, then the traits affecting insect-parasitoid interactions may exhibit an associated structure. the pea aphid (acyrthosiphon pisum) is a herbivorous insect species comprised ...	1999	28565548
reproductive isolation between sympatric races of pea aphids. i. gene flow restriction and habitat choice.	determining the extent and causes of barriers to gene flow between genetically divergent populations or races of single species is an important complement to post facto analyses of the causes of reproductive isolation between recognized species. sympatric populations of pea aphids (acyrthosiphon pisum harris, homoptera: aphididae) on alfalfa and red clover are highly genetically divergent and locally adapted. here, hierarchical estimates of population structure based on fst suggest that gene exc ...	1999	28565574
coleomegilla maculata (coleoptera: coccinellidae) predation on pea aphids promoted by proximity to dandelions.	the impact of a predator on its prey may depend on the presence of other species in the community. in particular, if predators are attracted to areas containing one prey species, another prey species may suffer greater predation if it occurs in the same areas. if the predator is omnivorous, this may occur even if one prey species is an animal and the other is a plant. we investigated the role of local dandelion densities on the impact of the predator coleomegilla maculata on pea aphids in alfalf ...	2000	28547224
chromosome analysis and molecular characterization of highly repeated dnas in the aphid acyrthosiphon pisum (aphididae, hemiptera).	despite the interest in aphid biology, information on chromatin organization of their holocentric chromosomes is still limited to few species. in order to fill this gap, we have performed an extensive survey on pea aphid mitotic chromosomes using both classical and molecular cytogenetic techniques. our results after silver, cma3 and dapi-staining, c-banding and fluorescent in situ hybridization (fish) using 28s rdna and 5s rdna as probes evidenced a tendency of repetitive dnas to be concentrated ...	2000	11138948
reproductive isolation between divergent races of pea aphids on two hosts. ii. selection against migrants and hybrids in the parental environments.	sympatric races of pea aphids on alfalfa and red clover are highly ecologically specialized and significantly reproductively isolated. much of the restriction of gene flow between the specialized populations is due to habitat choice behavior of the winged colonizers (via 1999). here, we document additional pre- and postmating reproductive isolation through selection against migrants and hybrids in the parental environments. first, a group of randomly chosen genotypes from each race that were exp ...	2000	11108590
clones of pea aphid, acyrthosiphon pisum (hemiptera: aphididae) distinguished using genetic markers, differ in their damaging effect on a resistant alfalfa cultivar.	cuf 101, a resistant cultivar of alfalfa, was exposed to 15 clones of acyrthosiphon pisum harris collected from alfalfa fields in three regions of france (east, south, central west) to determine whether the level of resistance varied across the different clones. the survival of alfalfa seedlings infested at the cotyledon stage was assessed using a standardized method. although no difference in seedling mortality was detected between clones grouped by region, there was a significant variation amo ...	2000	10948361
leaf surface waxbloom in pisum sativum influences predation and intra-guild interactions involving two predator species.	suppression of shared prey populations by insect predators can be influenced by interactions among these predators (intra-guild interactions). intra-guild interactions among predators attacking herbivores may be influenced by plant characteristics, but this possibility has not been examined. plant surface waxes are a ubiquitous and variable morphological feature that are known to affect insect predator behavior, and potentially in- fluence inter-predator interactions. to test this possibility we ...	2000	28308186
effect of nymphal diet on adult predation behavior in orius majusculus (heteroptera: anthocoridae).	the predatory bug orius majusculus (reuter) was reared on 2 different diets during the nymphal stages. the 1st group was exclusively offered eggs of ephestia kuehniella zeller (lepidoptera: pyralidae), a standard diet for o. majusculus production. the 2nd group was exclusively offered 4th instars of the pea aphid, acyrtosiphon pisum (harris). subsequently, adult predatory behavior in experimental arenas containing a. pisium was recorded using 2 video cameras. one camera permitted observation of ...	2000	10826169
salivary proteins of aphids, a pilot study on identification, separation and immunolocalisation.	salivary proteins (sps) of schizaphis graminum, acyrthosiphon pisum and myzus persicae were studied after probing and feeding on different artificial diets. salivary sheaths as well as apical lumps of saliva were found, presumably representing subsequently excreted saliva of different types. phenoloxidase, pectinase and peroxidase activities were detected by staining the enzyme-converted products, thus confirming these enzyme activities found earlier by others. proteinase and cellulase were not ...	2000	10818245
living on a high sugar diet: the fate of sucrose ingested by a phloem-feeding insect, the pea aphid acyrthosiphon pisum.	the natural diet of aphids, plant phloem sap, generally contains high concentrations of sucrose. when pea aphids (acyrthosiphon pisum) were fed on chemically defined diets containing sucrose radiolabelled in the glucose or fructose moiety, 2 to 12-fold and 87 to 110-fold more radioactivity was recovered from the tissues and honeydew, respectively, of aphids that ingested [u-(14)c-glucose]-sucrose than from those ingesting [u-(14)c-fructose]-sucrose. the total radioactivity recovered was 70% of t ...	2000	12770238
molecular characterization of the leucine plasmid from buchnera aphidicola, primary endosymbiont of the aphid acyrthosiphon pisum.	the complete sequence of the leucine plasmid of buchnera aphidicola from the aphid acyrthosiphon pisum (pleu-bap) is reported. its gene organization was concordant with those of other leucine plasmids of buchnera from aphids of the aphidini and macrosiphini tribes. three inverted repeats are present in pleu-bap. two of them are also present in pleu from the family aphididae: (i) sir1, located downstream the leucine operon, resembles a rho-independent terminator of transcription, and (ii) lir1, l ...	2000	10688696
prephenate dehydratase from the aphid endosymbiont (buchnera) displays changes in the regulatory domain that suggest its desensitization to inhibition by phenylalanine.	buchnera aphidicola, the prokaryotic endosymbiont of aphids, complements dietary deficiencies with the synthesis and provision of several essential amino acids. we have cloned and sequenced a region of the genome of b. aphidicola isolated from acyrthosiphon pisum which includes the two-domain aroq/phea gene. this gene encodes the bifunctional chorismate mutase-prephenate dehydratase protein, which plays a central role in l-phenylalanine biosynthesis. two changes involved in the overproduction of ...	2000	10781569
the influence of parasitism on wing development in male and female pea aphids.	wing formation in presumptive alate morphs (virginoparae and males) was observed for the pea aphid, acyrthosiphon pisum, exposed to attack by the parasitoid, aphidius ervi, at different stages of host development. morphological abnormalities in parasitized aphids such as complete apterization (development of a wingless form), formation of rudimentary wing buds, and deformed wings indicate a possible disruption of the endocrine system. changes in the body shape and the number of olfactory seconda ...	2000	10802097
host castration by aphidius ervi venom proteins.	the braconid aphidius ervi haliday (hymenoptera, braconidae) is an endophagous parasitoid of the pea aphid, acyrthosiphon pisum (harris) (homoptera, aphididae). parasitized host aphids show different degrees of castration, a response that is total when parasitoid oviposition takes place in first instar hosts. deleterious effects on the host reproductive system are already evident by 24h following parasitization, before egg hatching. the effect of parasitoid venom on a. pisum ovaries has been stu ...	2000	10802117
the secondary endosymbiotic bacterium of the pea aphid acyrthosiphon pisum (insecta: homoptera).	the secondary intracellular symbiotic bacterium (s-symbiont) of the pea aphid acyrthosiphon pisum was investigated to determine its prevalence among strains, its phylogenetic position, its localization in the host insect, its ultrastructure, and the cytology of the endosymbiotic system. a total of 14 aphid strains were examined, and the s-symbiont was detected in 4 japanese strains by diagnostic pcr. two types of eubacterial 16s ribosomal dna sequences were identified in disymbiotic strains; one ...	2000	10877764
behavioural thermoregulation in acyrthosiphon pisum (homoptera: aphididae): the effect of parasitism by aphidius ervi (hymenoptera: braconidae).	the effects of parasitisation by aphidius ervi on the thermoregulatory behaviour of the pea aphid acyrtosiphon pisum were studied in alfalfa fields and in an experimental thermal gradient. in the field, mummies were found exclusively on the adaxial surface of the upper leaves, and aphids in the mid canopy. the adaxial surface of the upper leaves was ca. 2 degrees c hotter that the mid-canopy. in the thermal gradient, the thermal effect (selected minus exposure temperature) was higher in magnitud ...	2001	11163929
spiroplasma symbiont of the pea aphid, acyrthosiphon pisum (insecta: homoptera).	from a laboratory strain of the pea aphid, acyrthosiphon pisum, we discovered a previously unknown facultative endosymbiotic bacterium. molecular phylogenetic analysis based on 16s ribosomal dna revealed that the bacterium is a member of the genus spiroplasma. the spiroplasma organism showed stable vertical transmission through successive generations of the host. injection of hemolymph from infected insects into uninfected insects established a stable infection in the recipients. the spiroplasma ...	2001	11229923
independent origins and horizontal transfer of bacterial symbionts of aphids.	many insect groups have obligate associations with primary endosymbionts: mutualistic bacteria that are maternally transmitted and derived from an ancient infection. often, the same insects are hosts to 'secondary' bacterial symbionts which are maternally transmitted but relatively labile within host lineages. to explore the dynamics of secondary symbiont associations in aphids, we characterized bacteria infecting 15 species of macrosiphine aphids using dna sequencing, diagnostic polymerase chai ...	2001	11251800
rickettsia associated with male-killing in a buprestid beetle.	many populations of the buprestid leaf-mining beetle, brachys tessellatus, from central south carolina, usa, show highly skewed sex ratios, ranging from 1.3 to 6.0 females per male. we have identified a rickettsia bacterium that is associated with sex ratio distortion (srd) and selective killing of male embryos in b. tessellatus. molecular assays of infection by this bacterium are highly associated with srd within families, and treatment with an antibiotic (tetracycline) increases the number of ...	2001	11520350
clonal variation and covariation in aphid resistance to parasitoids and a pathogen.	the potential rate of evolution of resistance to natural enemies depends on the genetic variation present in the population and any trade-offs between resistance and other components of fitness. we measured clonal variation and covariation in pea aphids (acyrthosiphon pisum) for resistance to two parasitoid species (aphidius ervi and a. eadyi) and a fungal pathogen (erynia neoaphidis). we found significant clonal variation in resistance to all three natural enemies. we tested the hypothesis that ...	2001	11681735
comparison of complete nucleotide sequences of genomic rnas of four soybean dwarf virus strains that differ in their vector specificity and symptom production.	soybean dwarf virus (sbdv) is divided into four strains, namely ys, yp, ds and dp. ys and yp cause yellowing in soybeans, while ds and dp cause dwarfing. ys and ds are transmitted by aulacorthum solani, while yp and dp are transmitted by acyrthosiphon pisum. to clarify the taxonomic relationship between the four strains and to classify sbdv into an appropriate genus in the luteoviridae, we determined the complete nucleotide sequences of genomic rnas of four isolates belonging to each of the stra ...	2001	11722012
featured organism: reductive evolution in bacteria: buchnera sp., rickettsia prowazekii and mycobacterium leprae.	obligate intracellular bacteria commonly have much reduced genome sizes compared to their nearest free-living relatives. one reason for this is reductive evolution: the loss of genes rendered non-essential due to the intracellular habitat. this can occur because of the presence of orthologous genes in the host, combined with the ability of the bacteria to import the protein or metabolite products of the host genes. in this article we take a look at three such bacteria whose genomes have been ful ...	2001	18628941
individual and population variation in invertebrates revealed by inter-simple sequence repeats (issrs).	pcr-based molecular markers are well suited for questions requiring large scale surveys of plant and animal populations. inter-simple sequence repeats or issrs are analyzed by a recently developed technique based on the amplification of the regions between inverse-oriented microsatellite loci with oligonucleotides anchored in microsatellites themselves. issrs have shown much promise for the study of the population biology of plants, but have not yet been explored for similar studies of animals. ...	2001	15455068
interactions between extrafloral nectaries, aphids and ants: are there competition effects between plant and homopteran sugar sources?	broad bean (vicia faba), an annual plant bearing extrafloral nectaries (efn) at the base of the upper leaves, is regularly infested by two aphid species, aphis fabae and acyrthosiphon pisum. efn and a. fabae are commonly attended by the ant, lasius niger, while ac. pisum usually remains uninfested. sugar concentration and sugar composition of extrafloral nectar did not change significantly after aphid infestation. the sugar concentration was significantly higher in efn (c. 271 µg µl(-1)) than in ...	2001	24577698
genetic linkage of ecological specialization and reproductive isolation in pea aphids.	the evolution of ecological specialization generates biological diversity and may lead to speciation. genetic architecture can either speed or retard this process. if resource use and mate choice have a common genetic basis through pleiotropy or close linkage, the resulting genetic correlations can promote the joint evolution of specialization and reproductive isolation, facilitating speciation. here we present a model of the role of genetic correlations in specialization and speciation, and tes ...	2001	11528477
why short-term bioassays are not meaningful--effects of a pesticide (imidacloprid) and a metal (cadmium) on pea aphids (acyrthosiphon pisum harris).	the life-table study on effects of a heavy metal, cd (100 and 200 mg kg-1 soil), and an insecticide, imidacloprid (4 and 40 g a.i. ha-1), on pea aphids revealed significant effects of both chemicals on life history traits and population dynamics. substantial differences in the action of the two chemicals and between the two doses of imidacloprid were observed. the pesticide caused high mortality at the beginning of the experiment, however some aphids were able to live for as long as control inse ...	2001	11383475
an aphid-borne bacterium allied to the secondary symbionts of whitefly.	bacterial 16s rdna amplified by pcr from the pea aphid acyrthosiphon pisum included a sequence with >98% similarity to secondary symbionts in the whitefly bemisia tabaci. the 'pea aphid bemisia-like bacterium' (pabs) and b. tabaci secondary symbionts are estimated to have diverged 17-34 million years ago, a time considerably more recent than the common ancestor of aphids and whitefly and suggestive of horizontal transmission of this bacterial lineage. pabs was scored in both the gut and ovaries ...	2001	11377772
glutathione s-transferases of aulacorthum solani and acyrthosiphon pisum: partial purification and characterization.	glutathione s-transferases (gst) play an important role in the detoxification of many substances including allelochemicals from plants. brassicaceae plants contain glucosinolates and emit volatile isothiocyanates which affect the gst system. a comparison of the gst of two aphid species, the generalist aulacorthum solani found on brassicaceae and the fabaceae specialist acyrthosiphon pisum, was made to try to explain their respective feeding behaviour. differences of gst were determined among the ...	2001	11337260
effect of temperature and cultivar on pea aphid, acyrthosiphon pisum (hemiptera: aphididae) life history.	life history parameters of the pea aphid, acyrthosiphon pisum were studied at five constant temperatures on two cultivars of peas, scout and sancho. the development and mortality of juveniles and the life-span, age-specific fecundity and survivorship of adult aphids were recorded and used to construct life tables. the juvenile development period (from birth to adulthood) was longest at 11.9 degrees c (16.8 days on cv. scout and 16.2 days on cv. sancho) and shortest at 26.7 degrees c (8.5 days on ...	2001	11228587
a sex-linked locus controls wing polymorphism in males of the pea aphid, acyrthosiphon pisum (harris).	discrete variation in wing morphology is a very common phenomenon in insects and has been used extensively in the past 50 years as a model to study the ecology and evolution of dispersal. wing morph determination can be purely genetic, purely environmental, or some combination of the two. the precise genetic determinants of genetically based wing morph variation are unknown. here we explore the genetic basis of wing polymorphism in the pea aphid, which can produce either winged or wingless males ...	2002	12399992
costs of resistance in insect-parasite and insect-parasitoid interactions.	most, if not all, organisms face attack by natural enemies and will be selected to evolve some form of defence. resistance may have costs as well as its obvious benefits. these costs may be associated with actual defence or with the maintenance of the defensive machinery irrespective of whether a challenge occurs. in this paper, the evidence for costs of resistance in insect-parasite and insect-parasitoid systems is reviewed, with emphasis on two host-parasitoid systems, based on drosophila mela ...	2002	12622330
the genetic architecture of ecological specialization: correlated gene effects on host use and habitat choice in pea aphids.	genetic correlations among phenotypic characters result when two traits are influenced by the same genes or sets of genes. by reducing the degree to which traits in two environments can evolve independently (e.g., lande 1979; via and lande 1985), such correlations are likely to play a central role in both the evolution of ecological specialization and in its link to speciation. for example, negative genetic correlations between fitness traits in different environments (i.e., genetic trade-offs) ...	2002	18707371
an experimental validation of orphan genes of buchnera, a symbiont of aphids.	although buchnera sp. aps, an intracellular symbiont of pea aphids, is a close relative of escherichia coli, its genome has been extensively modified because of its prolonged intracellular life. in our previous studies on the buchnera genome, computer analysis predicted three "orphan" genes, yba2, yba3, and yba4, which are open reading frames (orfs) with no homologs in the database. in this paper, we successfully validated all these orphan genes by rt-pcr and northern hybridization. the present ...	2002	11890702
estimating population size and transmission bottlenecks in maternally transmitted endosymbiotic bacteria.	many species of bacterial endosymbionts are acquired by animal hosts before birth, through direct transmission from mothers to eggs or embryos. this vertical transmission imposes a reduction in numbers or "bottleneck," and the size of this bottleneck affects the population structure and evolution of symbiotic lineages. we have estimated the size of the transmission bottleneck in buchnera, the bacterial symbiont of aphids, using basic light and electron microscopy techniques. by serial-sectioning ...	2002	12087426
influence of temperature on pea aphid acyrthosiphon pisum (hemiptera: aphididae) resistance to natural enemy attack.	the ability to resist or avoid natural enemy attack is a critically important insect life history trait, yet little is understood of how these traits may be affected by temperature. this study investigated how different genotypes of the pea aphid acyrthosiphon pisum harris, a pest of leguminous crops, varied in resistance to three different natural enemies (a fungal pathogen, two species of parasitoid wasp and a coccinellid beetle), and whether expression of resistance was influenced by temperat ...	2002	12191444
diversity and geographic distribution of secondary endosymbiotic bacteria in natural populations of the pea aphid, acyrthosiphon pisum.	in addition to the essential intracellular symbiotic bacterium buchnera, several facultative endosymbiotic bacteria called collectively secondary symbionts (s-symbionts) have been identified from the pea aphid acyrthosiphon pisum. we conducted an extensive and systematic survey of s-symbionts in japanese local populations of a. pisum using a specific pcr detection technique. five s-symbionts of a. pisum, pass, paus, pabs, rickettsia and spiroplasma, and two facultative endosymbionts universally ...	2002	12296954
plant-to-plant communication mediating in-flight orientation of aphidius ervi.	broad bean plants (viciafaba) infested by the pea aphid, acyrthosiphonpisum, play akey role in the in-flightorientation of the parasitoidaphidius ervi, by producing host-induced synomones (his). these volatiles are herbivore-specific and are systemically released from insect-free parts of an infested plant, suggesting the existence of an elicitor circulating throughout the plant. this study was designed to investigate whether the plant metabolic changes, leading to his biosynthesis and emission, ...	2002	12449500
pea aphid clonal resistance to the endophagous parasitoid aphidius ervi.	the physiological mechanism of resistance to the endophagous braconid aphidius ervi haliday (hymenoptera, braconidae) by a pink clone (pc) of acyrthosiphon pisum (harris) (homoptera, aphididae) has been investigated. comparative data on parasitoid development and associated host biochemical changes in the resistant pc aphids and in a susceptible green clone (gc) of a. pisum are reported. when the pc aphids were attacked as early 4th instars, the developing parasitoid larvae showed a strongly red ...	2002	12770044
metabolic and symbiotic interactions in amino acid pools of the pea aphid, acyrthosiphon pisum, parasitized by the braconid aphidius ervi.	aphidius ervi haliday (hymenoptera, braconidae) is an endophagous parasitoid of the pea aphid, acyrthosiphon pisum (harris) (homoptera, aphididae). this parasitoid strongly redirects host reproduction and metabolism to favour nutrition and development of its juvenile stages. parasite-regulated biosynthesis and mobilization of nitrogen metabolites determine a significant increase of host nutritional suitability. the aim of the present study was mainly to investigate the temporal changes of a. pis ...	2002	12770078
facultative bacterial symbionts in aphids confer resistance to parasitic wasps.	symbiotic relationships between animals and microorganisms are common in nature, yet the factors controlling the abundance and distributions of symbionts are mostly unknown. aphids have an obligate association with the bacterium buchnera aphidicola (the primary symbiont) that has been shown to contribute directly to aphid fitness. in addition, aphids sometimes harbor other vertically transmitted bacteria (secondary symbionts), for which few benefits of infection have been previously documented. ...	2003	12563031
selection by phage display of a variant mustard trypsin inhibitor toxic against aphids.	the mustard trypsin inhibitor, mti-2, is a potent inhibitor of trypsin with no activity towards chymotrypsin. mti-2 is toxic for lepidopteran insects, but has low activity against aphids. in an attempt to improve the activity of the inhibitor towards aphids, a library of inhibitor variants was constructed and cloned into the prlac3 phagemid vector. the library of 9.3 x 107 independent colonies was created by randomisation of a stretch of five consecutive codons in the reactive site. repeated sel ...	2003	12581313
effect of spatial heterogeneity on the role of coccinella septempunctata as an intra-guild predator of the aphid pathogen pandora neoaphidis.	the foraging behavior of starved and non-starved adult and larval coccinella septempunctata on groups of plants in the presence of pandora neoaphidis-infected acyrthosiphon pisum, uninfected aphids or a mixture of these two prey types was compared. in general results of these studies confirmed the results of previous work comparing foraging behavior on a smaller spatial scale in petri dishes. however, behaviors were modified in response to spatial complexity, prey quality, and the host plant. st ...	2003	12623308
a novel computerised image analysis method for the measurement of production of conidia from the aphid pathogenic fungus erynia neoaphidis.	a semi-automated method has been developed for the quantification and measurement of conidia discharged by the aphid pathogen erynia neoaphidis. this was used to compare conidiation by e. neoaphidis-mycosed pea aphid cadavers, mycelial plugs cut from agar plates, mycelial pellets from shake flasks and by mycelial pellets from different phases of liquid batch fermenter culture. aphid cadavers discharged significantly more and significantly smaller conidia than plugs or pellets. the volume of coni ...	2003	12644230
extraordinary proliferation of microorganisms in aposymbiotic pea aphids, acyrthosiphon pisum.	aposymbiotic pea aphids, which were deprived of their intracellular symbiotic bacterium, buchnera, exhibit growth retardation and no fecundity. high performance liquid chromatographic (hplc) analysis revealed that these aposymbiotic aphids, when reared on broad bean plants, accumulated a large amount of histamine. to assess the possibility of extraordinary proliferation of microorganisms other than buchnera, we enumerated eubacteria and fungi in aphids using the real-time quantitative pcr method ...	2003	12676551
characterization of a high-affinity binding site for the pea albumin 1b entomotoxin in the weevil sitophilus.	the toxicity of the pea albumin 1b (pa1b), a 37 amino-acid peptide extracted from pea seeds, for cereal weevils (sitophilus oryzae, sitophilus granarius and sitophilus zeamais) was recently discovered. the mechanism of action of this new entomotoxin is still unknown and potentially involves a target protein in the insect tissues. this work describes the characterization of a high-affinity binding site for pa1b in a microsomal fraction of sitophilus spp. extracts. purified pa1b was labeled to a h ...	2003	12755698
xerocomus chrysenteron lectin: identification of a new pesticidal protein.	xerocomus chrysenteron is an edible mushroom with insecticidal properties. in an earlier work, we found that proteins are responsible for this toxicity. here we describe the purification of a approximately 15 kda lectin, named xcl, from the mushroom. its cdna and gdna were cloned by pcr strategies and a recombinant form was expressed in escherichia coli. sequence alignments and sugar specificity showed that this protein is the third member of a new saline-soluble lectin family present in fungi. ...	2003	12787928
elucidation of the transmission patterns of an insect-borne bacterium.	quantitative data on modes of transmission are a crucial element in understanding the ecology of microorganisms associated with animals. we investigated the transmission patterns of a gamma-proteobacterium informally known as pea aphid bemisia-like symbiont (pabs), also known as t-type, which is widely but not universally distributed in natural populations of the pea aphid, acyrthosiphon pisum. the vertical transmission of pabs to asexual and sexual morphs and sexually produced eggs was demonstr ...	2003	12902222
host-based divergence in populations of the pea aphid: insights from nuclear markers and the prevalence of facultative symbionts.	in north america, the pea aphid acyrthosiphon pisum encompasses ecologically and genetically distinct host races that offer an ideal biological system for studies on sympatric speciation. in addition to its obligate symbiont buchnera, pea aphids harbour several facultative and phylogenetically distant symbionts. we explored the relationships between host races of a. pisum and their symbiotic microbiota to gain insights into the historical process of ecological specialization and symbiotic acquis ...	2003	12964998
developmental origin and evolution of bacteriocytes in the aphid-buchnera symbiosis.	symbiotic relationships between bacteria and insect hosts are common. although the bacterial endosymbionts have been subjected to intense investigation, little is known of the host cells in which they reside, the bacteriocytes. we have studied the development and evolution of aphid bacteriocytes, the host cells that contain the endosymbiotic bacteria buchnera aphidicola. we show that bacteriocytes of acyrthosiphon pisum express several gene products (or their paralogues): distal-less, ultrabitho ...	2003	14551917
diversity of bacteria associated with natural aphid populations.	the bacterial communities of aphids were investigated by terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis analysis of 16s rrna gene fragments generated by pcr with general eubacterial primers. by both methods, the gamma-proteobacterium buchnera was detected in laboratory cultures of six parthenogenetic lines of the pea aphid acyrthosiphon pisum and one line of the black bean aphid aphis fabae, and one or more of four previously described bacterial tax ...	2003	14660369
facultative symbionts are associated with host plant specialization in pea aphid populations.	the pea aphid, acyrthosiphon pisum, shows significant reproductive isolation and host plant specialization between populations on alfalfa and clover in new york. we examine whether specialization is seen in pea aphids in california, and whether fitness on alternative host plants is associated with the presence of bacterial symbionts. we measured the fitness of alfalfa- and clover-derived aphids on both types of plants and found no evidence for specialization when all aphid lineages were consider ...	2003	14667385
transmission of symbiotic bacteria buchnera to parthenogenetic embryos in the aphid acyrthosiphon pisum (hemiptera: aphidoidea).	all phloem-feeding aphids have an absolute requirement for their primary bacterial symbionts buchnera sp. the bacteria are transmitted vertically to either embryos in the viviparous morph or to eggs in the oviparous morph, with the implication that the symbiont population regularly passes through a genetic 'bottleneck', i.e. only a small proportion of the maternal symbiont population is transmitted to offspring. in this paper, we visualise this process in viviparous aphids using a specific immun ...	2003	18089009
the n-terminal region of the readthrough domain is closely related to aphid vector specificity of soybean dwarf virus.	abstract it has been speculated that the n-terminal half of the readthrough domain (rtd) encoded by open reading frame 5 of soybean dwarf virus (sbdv) is related to the vector specificity. to further investigate this hypothesis, transmissibility via aphids was tested on 17 sbdv isolates and comparisons of the deduced amino acid sequences of the coat protein (cp) and other proteins encoded by the rtd were made between these isolates. isolates were distinguished into four strains: ys, causing yell ...	2003	18943620
plant waxy bloom on peas affects infection of pea aphids by pandora neoaphidis.	this study examined the effects of the surface wax bloom of pea plants, pisum sativum, on infection of pea aphids, acyrthosiphon pisum, by the fungal pathogen pandora neoaphidis. in prior field surveys, a higher proportion of p. neoaphidis-killed pea aphids (cadavers) had been observed on a pea line with reduced wax bloom, as compared with a sister line with normal surface wax bloom. laboratory bioassays were conducted in order to examine the mechanisms. after plants of each line infested with a ...	2003	14726238
changing partners in an obligate symbiosis: a facultative endosymbiont can compensate for loss of the essential endosymbiont buchnera in an aphid.	almost all aphids harbour an endosymbiotic bacterium, buchnera aphidicola, in bacteriocytes. buchnera synthesizes essential nutrients and supports growth and reproduction of the host. over the long history of endosymbiosis, many essential genes have been lost from the buchnera genome, resulting in drastic genome reduction and the inability to live outside the host cells. in turn, when deprived of buchnera, the host aphid suffers retarded growth and sterility. buchnera and the host aphid are ofte ...	2003	14728775
diapause in the pea aphid (acyrthosiphon pisum) is a slowing but not a cessation of development.	many insects undergo a period of arrested development, called diapause, to avoid seasonally recurring adverse conditions. whilst the phenology and endocrinology of insect diapause have been well studied, there has been comparatively little research into the developmental details of diapause. we investigated developmental aspects of diapause in sexually-produced embryos of the pea aphid, acyrthosiphon pisum.	2003	12908880
midgut adaptation and digestive enzyme distribution in a phloem feeding insect, the pea aphid acyrthosiphon pisum.	transmission electron micrographs of the pea aphid midgut revealed that its anterior region has cells with an apical complex network of lamellae (apical lamellae) instead of the usual regularly-arranged microvilli. these apical lamellae are linked to one another by trabeculae. modified perimicrovillar membranes (mpm) are associated with the lamellae and project into the lumen. trabeculae and mpm become less conspicuous along the midgut. the most active a. pisum digestive enzymes are membrane-bou ...	2003	12770012
the interplay between density- and trait-mediated effects in predator-prey interactions: a case study in aphid wing polymorphism.	natural enemies not only influence prey density but they can also cause the modification of traits in their victims. while such non-lethal effects can be very important for the dynamic and structure of prey populations, little is known about their interaction with the density-mediated effects of natural enemies. we investigated the relationship between predation rate, prey density and trait modification in two aphid-aphid predator interactions. pea aphids (acyrthosiphon pisum, harris) have been ...	2003	12698353
effects of a simple plant morphological mutation on the arthropod community and the impacts of predators on a principal insect herbivore.	plant features that enhance predator effectiveness can be considered extrinsic-resistance factors because they result in reduced insect herbivory. in this paper we test the hypothesis that reduced epicuticular wax (ew) in pisum sativum l. is an extrinsic-resistance factor contributing to field resistance to acyrthosiphon pisum (harris). we monitored pea aphid populations in the field on reduced ew and normal ew near isolines of peas for two seasons and confirmed that aphid populations are lower ...	2003	12647102
toxicity to the pea aphid acyrthosiphon pisum of anti-chymotrypsin isoforms and fragments of bowman-birk protease inhibitors from pea seeds.	aphids feed on a protein-poor diet and are insensitive to several serine protease inhibitors. however, among the bowman-birk family of plant trypsin inhibitors (bbi), some members display significant toxicity to the pea aphid acyrthosiphon pisum. a bbi isoform purified from pea seeds (psti-2) displays an ic50 of 41 microm and a lc50 of 48 microm at 7 days. our data show that the chymotrypsin-directed active site from these bifunctional inhibitors is responsible for this activity, and that artifi ...	2003	12609515
identification of a gene overexpressed in aphids reared under short photoperiod.	most aphids develop a cyclic parthenogenesis life-cycle. after several generations of viviparously produced parthenogenetic females, follows a single annual generation of sexual individuals, usually in autumn, that mate and lay the sexual eggs. shortening of photoperiod at the end of the summer (together with temperature) is a key factor inducing the sexual response. currently no genes involved in the cascade of events that lead to the appearance of sexual forms have been reported. after a diffe ...	2003	12609514
a comparison of parthenogenetic and sexual embryogenesis of the pea aphid acyrthosiphon pisum (hemiptera: aphidoidea).	aphids exhibit divergent modes of embryogenesis during the sexual and asexual phases of the life cycle. to explore how a single genome can give rise to these alternative developmental modes, we have initiated embryological studies of the pea aphid, acyrthosiphon pisum. here we present a detailed description of parthenogenetic, viviparous embryonic development in the pea aphid. we compare and contrast development of the parthenogenetic embryo with that of the embryo resulting from sexual reproduc ...	2003	12548543
nutritional plasticity of the predatory ladybeetle harmonia axyridis (coleoptera: coccinellidae): comparison between natural and substitution prey.	the predatory coccinellid harmonia axyridis is a polyphagous species, efficient at controlling certain aphid species and already commercialized in europe for that purpose. the complete development of this predator can be accomplished using the aphid acyrthosiphon pisum or ephestia kuehniella eggs as substitution prey. biochemical analyses were conducted on the proteins, lipids, and carbohydrates of these two different prey species. e. kuehniella eggs were 2 times richer in amino acids than a. pi ...	2003	12529863
binding of the insecticidal lectin concanavalin a in pea aphid, acyrthosiphon pisum (harris) and induced effects on the structure of midgut epithelial cells.	concanavalin a (lectin from canavalia ensiformis l., cona) has previously been shown to act as a feeding inhibitor for acyrthosiphon pisum, the pea aphid. in the present study a range of histochemical and biochemical techniques were used to elucidate the target tissues and binding sites of the lectin in the aphid. diet uptake was evaluated using a radioactive tracer (14c-methylated inulin) and demonstrated that adults were capable of ingesting high quantities of the toxin (approx. 1 microg over ...	2004	15670861
per os efficacy of ajuga extracts against sucking insects.	we studied the efficacy of water-soluble extracts from four ajuga spp on the post-embryonic development of two exopterygota (sucking insect) species. to allow comparison between different ajuga species, results are expressed in terms of quantity of plant extracted per litre of test solution. crude methanolic extracts of all ajuga plants tested, with the exception of a genevensis, showed considerable per os efficacy against larvae of both dysdercus cingulatus f and acyrthosiphon pisum (harris) ev ...	2004	15532684
olfactory responses to aphid and host plant volatile releases: (e)-beta-farnesene an effective kairomone for the predator adalia bipunctata.	the volatiles released from several aphid and host plant species, alone or associated, were studied for their infochemical role in prey location. using a four-arm olfactometer, the attraction of several combinations of three aphid (myzus persicae, acyrthosiphon pisum, and brevicoryne brassicae) and three plant (vicia faba, brassica napus, and sinapis alba) species toward adalia bipunctata larvae and adults was observed. both predatory larvae and adults were attracted only by a. pisum and m. pers ...	2004	15260221
delineating the effects of a plant trait on interactions among associated insects.	plant traits can affect ecological interactions between plants, herbivores, and predators. our study tests whether reduced leaf wax in peas alters the interaction between the pea aphid ( acyrthosiphon pisum), a foliar-foraging predator (a lady beetle, hippodamia convergens) and a ground-foraging predator (a ground beetle, poecilus scitulus). we performed a 2 x 2 x 2 factorial experiment in which wax level, presence of h. convergens, and presence of p. scitulus were manipulated. experimental aren ...	2004	14740292
rapid quantification of juvenile hormones and their metabolites in insect haemolymph by liquid chromatography-mass spectrometry (lc-ms).	a simple, fast and sensitive method was developed for routine determination of juvenile hormone (jh), jh diols and jh acids in insect haemolymph, by liquid chromatography-mass spectrometry (lc-ms). sample clean-up involves the precipitation of proteins by methanol/isooctane (1:1, v/v), centrifugation and partial evaporation of the organic solvents. since jh is bound to a carrier protein in the haemolymph, a binding protein (bp) assay was performed to ensure jh is removed during precipitation. th ...	2004	15057500
the role of semiochemicals in the avoidance of the seven-spot ladybird, coccinella septempunctata, by the aphid parasitoid, aphidius ervi.	the role of semiochemicals in mediating intraguild interactions between the seven-spot ladybird, coccinella septempunctata, and the aphid parasitoid, aphidius ervi, was investigated. female parasitoids avoided leaves visited by c. septempunctata adults and larvae during the previous 24 hr. ethanol extracts of c. septempuntata adults and larvae also induced avoidance responses by a. ervi. two of the hydrocarbons identified by gas chromatography (gc) and coupled gc-mass spectrometry (gc-ms), n-tri ...	2004	15303317
the evolutionary fate of nonfunctional dna in the bacterial endosymbiont buchnera aphidicola.	reduction of the genome size in endosymbiotic bacteria is the main feature linked to the adaptation to a host-associated lifestyle. we have analyzed the fate of the nonfunctional dna in buchnera aphidicola, the primary endosymbiont of aphids. at least 164 gene losses took place during the recent evolution of three b. aphidicola strains, symbionts of the aphids acyrthosiphon pisum (bap), schizaphis graminum (bsg), and baizongia pistacia (bbp). a typical pattern starts with the inactivation of a g ...	2004	15317875
plum pox in north america: identification of aphid vectors and a potential role for fruit in virus spread.	abstract thirteen aphid species were tested for their ability to transmit pennsylvania isolates of plum pox virus (ppv) collected in columbia (penn-3), franklin (penn-4), and york (penn-7) counties, pa. four species, aphis fabae, a. spiraecola, brachycaudus persicae, and myzus persicae, consistently transmitted ppv in preliminary transmission tests. two species, metopolophium dirhodum and rhopalosiphum padi, were occasional inefficient vectors. toxoptera citricida, from florida, also was an effe ...	2004	18943108
the population genetics of a biological control introduction: mitochondrial dna and microsatellie variation in native and introduced populations of aphidus ervi, a parisitoid wasp.	introductions of biological control agents may cause bottlenecks in population size despite efforts to avoid them. we examined the population genetics of aphidius ervi (hymenoptera: braconidae), a parasitoid that was introduced to north america from western europe in 1959 to control pea aphids. to explore the phylogeographical relationships of a. ervi we sequenced 1249 bp of mitochondrial dna (mtdna) from 27 individuals from the native range and 51 individuals from the introduced range. most ind ...	2004	14717891
arthropod diversity in peas with normal or reduced waxy bloom.	crop traits can alter economically important interactions between plants, pests, and biological control agents. for example, a reduced waxy bloom on the surface of pea plants alters interactions between pea aphids and their natural enemies. in this study, we assess whether the effect of wax reduction extends beyond the 2 or 3 arthropod species closely associated with the plants and into the structure of the broader arthropod community of over 200 taxa at our site. we sampled arthropods on lines ...	2004	15861234
regulation of transcription in a reduced bacterial genome: nutrient-provisioning genes of the obligate symbiont buchnera aphidicola.	buchnera aphidicola, the obligate symbiont of aphids, has an extremely reduced genome, of which about 10% is devoted to the biosynthesis of essential amino acids needed by its hosts. most regulatory genes for these pathways are absent, raising the question of whether and how transcription of these genes responds to the major shifts in dietary amino acid content encountered by aphids. using full-genome microarrays for b. aphidicola of the host schizaphis graminum, we examined transcriptome respon ...	2005	15937185
rickettsia symbiont in the pea aphid acyrthosiphon pisum: novel cellular tropism, effect on host fitness, and interaction with the essential symbiont buchnera.	in natural populations of the pea aphid acyrthosiphon pisum, a facultative bacterial symbiont of the genus rickettsia has been detected at considerable infection frequencies worldwide. we investigated the effects of the rickettsia symbiont on the host aphid and also on the coexisting essential symbiont buchnera. in situ hybridization revealed that the rickettsia symbiont was specifically localized in two types of host cells specialized for endosymbiosis: secondary mycetocytes and sheath cells. e ...	2005	16000822
response of the entomopathogenic fungus pandora neoaphidis to aphid-induced plant volatiles.	we used a model plant-aphid system to investigate whether the aphid-specific entomopathogenic fungus pandora neoaphidis responds to aphid-induced defence by the broad-bean plant, vicia faba. laboratory experiments indicated that neither in vivo sporulation, conidia size nor the in vitro growth of p. neoaphidis was affected by acyrthosiphon pisum-induced v. faba volatiles. the proportion of conidia germinating on a. pisum feeding on previously damaged plants was significantly greater than on aphi ...	2005	16005016
pandora neoaphidis transmission and aphid foraging behaviour.	pandora neoaphidis is an aphid-specific entomopathogen that produces infective conidia. as aphid movement increases, so does the likelihood of contact with conidia. volatile distress signals released in response to aphid infestation as an indirect defence against herbivory may affect aphid foraging and, therefore, the fungus-aphid interaction. in this study, two different methods were used to investigate the effect of plant volatiles and p. neoaphidis-sporulating cadavers on (1) the colonisation ...	2005	16039666