Search

Some leafmining fly species are pests of agricultural and ornamental plants but they also include many species with little economic importance. The taxonomy of leafmining flies is often challenging because of putative cryptic species. Following new outbreaks of Liriomyza (Diptera:Agromyzidae) in Australia, we here characterize 13 dipteran leafminer species collected from Australia based on cytochrome c oxidase subunit 1 (COI) DNA barcodes, and we compare these with overseas data. We confirm barcodes of nine species from the Agromyzidae (Liriomyza sativae, L. huidobrensis, L. trifolii, L. bryoniae, L. chinensis, L. brassicae, L. chenopodii, Phytomyza plantaginis and P. syngenesiae) and one species from the Drosophilidae (Scaptomyza flava); we describe new haplotypes for some of these species. Furthermore, we provide the first DNA barcodes for two species (Cerodontha milleri and Phytoliriomyza praecellens) from the Agromyzidae and one species (Scaptomyza australis) from the Drosophilidae. These findings provide a baseline for DNA-based identification of pest Liriomyza incursions spreading across the Australian east coast in relation to other species already present in Australia.

The diversity of herbivorous insects is attributed to their propensity to specialize on toxic plants. In an evolutionary twist, toxins betray the identity of their bearers when herbivores co-opt them as cues for host-plant finding, but the mechanisms underlying this process are poorly understood. We focused onScaptomyza flava, an herbivorous drosophilid specialized on isothiocyanate (ITC)-producing (Brassicaceae) plants, and identifiedOr67bparalogs that were triplicated as mustard-specific herbivory evolved. Using heterologous systems for the expression of olfactory receptors, we found thatS. flavaOr67bs, but not homologs from microbe-feeding relatives, responded selectively to ITCs, each paralog detecting different ITC subsets. Consistent with this,S. flavawas attracted to ITCs, as wasDrosophila melanogasterexpressingS. flavaOr67b3 in the homologousOr67bolfactory circuit. Thus, our results show that plant toxins were likely co-opted as olfactory attractants through gene duplication and functional specialization (neofunctionalization and subfunctionalization) in drosophilid flies.

Scaptomyza flava (FALLÉN, 1823) M a t e r i a l u n t e r s u c h t: 2♀♀, 14.vi.2007, Bremen, Teiche w Neustädter Hafen [MTB 2818.3+2918.1]; 1♂, 9.vi.2007, Ausgleichsflächen Coldam [MTB 2710.3]; 1♀, 29.vii.2018, Bachbett 1.0 km wnw Sonnenberg [MTB 4229.1]; 1♀, 22.v.2005, Bachtal 500 m s Hankenberge [MTB 3814.2]; 1♀, 5.vii.2008, Badestrand Neuharlingersiel [MTB 2212.3]; 1♂ 1♀, 5.vii.2008, Badestrand sö Vosslaper Groden [MTB 2414.2]; 3♂♂ 3♀♀, 17.v.2007, Bassenfleth [MTB 2323.3]; 1♂, 2.viii.2018, Bodetal sö Braunlage [MTB 4229.4]; 1♀, 9.vii.2006, Bohrenberg 1 km w Salzderhelden [MTB 4125.4]; 1♀, 21.vii.2009, Borkum, Primärdünen und Dünentäler Nordweststrand [MTB 2306.3]; 1♀, 17.vii.2003, Brache bei Hauen [MTB 2408.3]; 2♀♀, 10.vi.2007, Brachfläche Leschede [MTB 3509.4]; 3♂♂, 8.vi.2007, Dollart, Bohrinsel [MTB 2709.1]; 2♂♂ 3♀♀, 8.vi.2007, Dollart, Röhrichte w Pogum [MTB 2609.3]; 1♂, 30.v.2009, Düte bei Brücke L89 s Hellern [MTB 3713.2]; 1♂ 2♀♀, 8.vi.2007, Dyksterhusen bei Bohrinsel [MTB 2709.1]; 1♀, 2.viii.2018, Eckeraue zw. Eckertal und Eckermühle [MTB 4029.4]; 1♀, 29.vii.2007, Elbufer n Walmsburg [MTB 2731.1]; 1♀, 15.vii.2009, Elbvorland s Drage [MTB 2527.4]; 1♂, 1.viii.2018, Elsbachtal bei Zorge [MTB 4329.4]; 1♀, 10.vi.2007, Ems 1 km ö Emsbüren (Emshock) [MTB 3610.1]; 1♂, 8.vii.2007, Erlenbruch direkt w Bad Rothenfelde [MTB 3815.3]; 1♂, 31.v.2008, dito; 1♀, 31.v.2009, dito; 1♂ 1♀, 10.vi.2018, Feuchtwiesen zwischen Wennekath und Süttorf [MTB 2729.4]; 1♀, 18.v.2007, Fischteiche 300 m ö Klein-Nindorf [MTB 2523.4]; 1♀, 12.v.2008, Gartower See, Westufer [MTB 2934.4]; 1♀, 29.vii.2007, Geesthang 1 km wnw Walmsburg [MTB 2730.2+2730.4+2731.1+2731.3]; 1♂, 1.viii.2018, Goslarsche Grund an L601, 6 km ssw Braunlage [MTB 4329.2]; 2♀♀, 21.vi.2008, Grosser Sonnenberg bei St. Andreasberg [MTB 4229.1]; 1♀, 30.vi.2006, Heseler Wald [MTB 2611.4]; 1♀, 1.viii.2018, Hundertmorgenwiese 1,5 km sö Zorge [MTB 4329.4]; 1♀, 12.vii.2006, Ihlower Forst [MTB 2510.4+2610.2]; 1♀, 16.vi.2007, Im Rohden 1 km ö Barterode [MTB 4424.2+4424.4]; 1♀, 28.vii.2018, Itelteich sw Walkenried [MTB 4429.2]; 3♂♂, 13.vi.2004, Kleiner Freeden ö Bad Iburg [MTB 3814.1]; 1♀, 9.vi.2018, Laascher Insel [MTB 2934.3+2934.4]; 1♀, 19.iv.2008, Leer, Evenburgpark [MTB 2710.4]; 1♂, 24.vii.2008, dito; 1♂, 15.vi.2018, Norderney, Brachfläche w Hafen [MTB 2208.4]; 2♂♂, 16.vi.2018, Norderney, Dünen 2 km onö Leuchtturm [MTB 2209.4]; 2♂♂, 16.vi.2018, Norderney, Dünen-Salzwiesen-Übergang 2 km onö Leuchtturm [MTB 2209.4]; 1♀, 16.vi.2018, Norderney, Kurpark n Marienstrasse [MTB 2208.4]; 1♀, 15.vi.2018, Norderney, Pferdehof Junkmann [MTB 2209.3]; 1♀, 15.vi.2018, Norderney, Südstrandpolder [MTB 2209.3]; 5♂♂, 15.vi.2018, Norderney, Wald Weststrand [MTB 2208.4]; 1♀, 21.vi.2008, NSG Bergwiesen bei Jordanshöhe 1 km nö St. Andreasberg [MTB 4229.3]; 1♀, 22.iv.2005, Rechter Brok [MTB 2714.1]; 1♂, 29.iii.2003, Rorichumer Tief bei Ayenwolde [MTB 2610.4]; 1♂ 1♀, 8.vi.2004, Rorichumer Tief bei Sieve 2 km ö Tergaste [MTB 2610.4]; 1♀, 2.vi.2003, Rysumer Nacken [MTB 2608.1+2608.3]; 1♂ 2♀♀, 25.vi.2006, dito; 1♂ 6♀♀, 2.vii.2006, dito; 4♂♂ 2♀♀, 28.v.2007, dito; 1♀, 17.vii.2003, Salzwiesen bei Pilsumer Leuchtturm [MTB 2408.3+2409.1]; 1♀, 27.vi.2003, Salzwiesen Manslagter Nacken [MTB 2508.1+2508.3]; 1♀, 28.v.2007, dito; 2♂♂, 3.vii.2005, Schwingetal Wiepenkathen [MTB 2422.2]; 1♂, 31.vii.2018, Siebertal 2,4 km sw Sieber [MTB 4328.1]; 1♂, 31.vii.2018, Sösetal n Kamschlacken [MTB 4228.3]; 2♂♂, 29.vii.2018, Sonnenberg, Skipisten [MTB 4229.1]; 1♂ 3♀♀, 19.vi.2005, Sperrluttertal, 360 m, bei Bad Lauterberg [MTB 4329.1]; 1♂, 19.v.2004, Tal der Holzminde, 250m [MTB 4222.2]; 1♀, 6.viii.2008, Taube Elbe W Penkefitz [MTB 2832.4]; 1♀, 17.vi.2005, Trockenrasen W Waake [MTB 4426.1]; 1♀, 18.vi.2005, Wald 1 km wnw Mackenrode [MTB 4429.1]. L i t e r a t u r: Bremen: BUHR (1933). — Niedersachsen: ALFKEN (1924 [unter flaveola (MEIGEN, 1830)]), BÄCHLI (1988), FRANZEN et al. (1997), KRÖBER (1935 [unter apicalis HARDY, 1849]), PRESCHER & BÜCHS (2000), RUDZINSKI (1995), SCHNEIDER (1898 [unter flaveola (MEIGEN, 1830)]). Scaptomyza flava ist eine häufige Art, die in ganz Niedersachsen verbreitet ist. Sie kommt vor allem in offenen Lebenräumen vor. Beispielsweise wurde sie auf Trockenrasen, Feuchtgrünland, Salzwiesen, Dünen oder an Ufern gesammelt., Published as part of Jens-H, 2020, Die Fruchtfliegen Niedersachsens und Bremens (Diptera, Drosophilidae) The Fruit Flies (Diptera, Drosophilidae) of Lower Saxony and, pp. 475-499 in Linzer biologische Beiträge 52 (1) on pages 488-489, DOI: 10.5281/zenodo.5275110, {"references":["BUHR H. (1933): Mecklenburgische Minen II. Coleopteren-, Tenthrediniden- und Dipteren- Minen. - Stettiner Entomologische Zeitung 94: 47 - 96.","ALFKEN J. D. (1924): Die Insekten des Memmert. Zum Problem der Besiedlung einer neuentstehenden Insel. - Abhandlungen des Naturwissenschaftlichen Vereins zu Bremen 25: 358 - 481.","BACHLI G. (1988): Die Drosophiliden-Fauna von Mellum und Memmert. - Drosera 1988: 287 - 292.","FRANZEN J., WEBER G., BUCHS W. & O. LARINK (1997): Langzeiteinfluss von Pflanzenschutzmitteln auf Dipteren mit bodenlebenden Entwicklungsstadien. - Berichte uber Landwirtschaft 75: 291 - 328.","KROBER O. (1935): Dipterenfauna von Schleswig-Holstein und den benachbarten westlichen Nordseegebieten. II. Teil: Diptera Brachycera: Pyrgotidae bis Milichiidae. - Verhandlungen des Vereins fur naturwissenschaftliche Heimatforschung zu Hamburg 24: 45 - 80.","RUDZINSKI H. - G. (1995): Zum Vorkommen von Dipteren auf einem Hausbalkon. Teil III: Brachycera. - Entomologische Zeitschrift. Frankfurt a. M. 105: 235 - 244.","SCHNEIDER O. (1898): Die Tierwelt der Nordsee-Insel Borkum unter Berucksichtigung der von den ubrigen ostfriesischen Inseln bekannten Arten. - Abhandlungen des Naturwissenschaftlichen Vereins zu Bremen 16: 1 - 174."]}

One-quarter of extant Eukaryotic species are herbivorous insects, yet the genomic basis of this extraordinary adaptive radiation is unclear. Recently-derived herbivorous species hold promise for understanding how colonization of living plant tissues shaped the evolution of herbivore genomes. Here, we characterized exceptional patterns of evolution coupled with a recent (Arabidopsis thaliana) in the fly genusScaptomyza,nested within the paraphyletic genusDrosophila. We discovered a radiation of mustard-specializedScaptomyzaspecies, comparable in diversity to theDrosophila melanogasterspecies subgroup. Stable isotope, behavioral, and viability assays revealed these flies are obligate herbivores. Genome sequencing of one species,S. flava,revealed that the evolution of herbivory drove a contraction in gene families involved in chemosensation and xenobiotic metabolism. Against this backdrop of losses, highly targeted gains (“blooms”) were found in Phase I and Phase II detoxification gene sub-families, including glutathioneS-transferase (Gst) and cytochrome P450 (Cyp450) genes.S. flavahas more validated paralogs of a singleCyp450(N=6 forCyp6g1) andGst(N=5 forGstE5-8) than any other drosophilid. Functional studies of theGstrepertoire inS. flavashowed that transcription ofS. flava GstE5-8paralogs was differentially regulated by dietary mustard oils, and of 22 heterologously expressed cytosolicS. flavaGST enzymes, GSTE5-8 enzymes were exceptionally well-adapted to mustard oil detoxificationin vitro.One, GSTE5-8a, was an order of magnitude more efficient at metabolizing mustard oils than GSTs from any other metazoan. The serendipitous intersection of two genetic model organisms,DrosophilaandArabidopsis,helped illuminate how an insect genome was remodeled during the evolutionary transformation to herbivory, identifying mechanisms that facilitated the evolution of the most diverse guild of animal life.SIGNIFICANCE STATEMENTThe origin of land plants >400 million years ago (mya) spurred the diversification of plant-feeding (herbivorous) insects and triggered an ongoing chemical co-evolutionary arms race. Because ancestors of most herbivorous insects first colonized plants >200 mya, the sands of time have buried evidence of how their genomes changed with their diet. We leveraged the serendipitous intersection of two genetic model systems: a close relative of yeast-feeding fruit fly (Drosophila melanogaster), the “wasabi fly” (Scaptomyza flava), that evolved to consume mustard plants includingArabidopsis thaliana. The yeast-to-mustard dietary transition remodeled the fly’s gene repertoire for sensing and detoxifying chemicals. Although many genes were lost, some underwent duplications that encode the most efficient detoxifying enzymes against mustard oils known from animals.

We determined the host range of the parasitoid Trichomalus perfectus (Walker), a candidate for classical biological control of cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), an important pest of canola in Canada. Studies were conducted in Europe and in North America. In laboratory experiments, the levels of parasitism (acceptance) of Ceutorhynchus turbatus Schultze, C. cardariae Korotyaev, C. omissus Fall and C. querceti (Gyllenhal) by T. perfectus were not significantly different than of the target host C. obstrictus. Although C. typhae (Herbst), C. pallidactylus (Marsham), C. americanus Buchanan, C. neglectus Blatchely and Ceutorhynchus sp. nr. nodipennis were parasitised by T. perfectus, the levels of parasitism were significantly lower on these species than on C. obstrictus. Ceutorhynchus peyerimhoffi Hustache, C. erysimi (Fabricius), C. alliariae H. Brisout, C. roberti Gyllenhal, Mogulones borraginis (Fabricius), Mononychus vulpeculus (Fabricius) and the leaf-mining fly Scaptomyza flava ...

Herbivorous insects exhibit strong feeding preferences when choosing among plant genotypes, yet experiments to map loci mediating plant susceptibility to herbivory rarely incorporate host choice. To address this gap, we applied genome-wide association (GWA) mapping to uncover genetic polymorphisms mediating damage from foraging insects (two populations ofScaptomyza flava) across a mixture ofArabidopsis thalianagenotypes in experimental enclosures. The effect of chemical defenses (glucosinolates) on herbivory depended on herbivore genotype. Unlike many studies that minimize the effects of host choice behavior, we also found a large effect of plant size on herbivory—likely through its effect on plant apparency—that was independent of herbivore genotype. These herbivory-associated loci are polymorphic at fine spatial scales, and thus have potential to shape variation in herbivory within natural populations. We also show that the polymorphism with the largest effect on herbivory underlies adaptive latitudinal variation inArabidopsisplant size across Europe. Overall, our results provide genetic support for ecological observations that variation in both chemical defenses and non-canonical defense traits (e.g., plant size and phenology) jointly shapes plant-herbivore interactions.

Historically, handling insects usually involved their being killed as early studies used these organisms for work on genetics, physiology and/or pesticide bioassays. With the advancement of these research topics, the development of behavioral studies and the sensitivity of culturally important, threatened or endangered species, approaches that focus on non-lethal preparation of the insects for experimentation have become important. Anesthesia has been used as one of these non-lethal approaches to provide researchers flexibility when designing experiments. Two common anesthetics used for insect experimentation are carbon dioxide and chilling. These anesthetics have been used frequently in the literature but their sub-lethal effects on insects are poorly studied. Another that has potential for experimental use is triethylamine (TEA). This chemical shows promise because of its ease of use and potency as an insect anesthetic, but evidence, if any, of the sub-lethal effects is almost non-existent in the literature. A series of experiments was carried out to find the optimal exposure times and/or concentrations for each of these three approaches. Once an optimal treatment was found for each approach, these were compared to each other in a subsequent experiment. It was found that TEA is a far superior anesthetic when recording/observing fly longevity.

Populations of the leafminer, Scaptomyza flava, were monitored fortnightly in turnip plantings at Pukekohe, south Auckland, for more than 2 years. The fly, and its main parasitoid, Asobara sp. (nr. persimilis) (Hymenoptera: Braconidae), were present throughout the year, with populations peaking in midsummer on spring plantings. A replicated field trial, comparing four planting dates, suggests that new leaves on young plants and on flowering stems were favoured for oviposition by the leafminer. In another experiment, young leaves of flowering Gypsophila sp. were more suitable for oviposition and larval survival than leaves of younger non-flowering plants. Measurements of the mandible and associated skeleton confirmed the existence of three leafminer larval instars. The parasitoid has a partial winter diapause. In midsummer, it achieved over 80% parasitism. A survey found Asobara parasitism of S. flava was restricted to a small area of south Auckland. These data, together with its monophagy in New Zealand a...

The availability of model microbial pathogens and plants has been key to characterizing resistance and virulence pathways and to shedding light on the mechanisms of host–parasite interactions and co-evolution (e.g. Allen et al. 2004, Science306, 1957–1960; Bergelson et al. 2001, Science292, 2281–2285). However, the absence of genetically tractable arthropod parasites of model plants has impeded so far our ability to gain better insights into the mechanisms, evolution and ecological consequences of plant–herbivore interactions. In this issue of Molecular Ecology, Whiteman et al. (2011) highlight fascinating features of a drosophilid fly, Scaptomyza flava, that feeds on the model plant Arabidopsis thaliana. They explore the potential of this system for studying insect–plant interactions with a clever mix of phenotypic and genetic experiments providing a comprehensive and persuasive argument for the validity of this model system. This study sets the ground for key developments in the unravelling of mechanisms involved in (i) plant–insect interactions and co-evolution, and (ii) transition to herbivory in arthropods and evolution of endophagous lifestyles.

European leafminer, Scaptomyza flava (Fallen), is an important pest of brassicas, peas and gypsophila in New Zealand. This study examined the mating behaviour of this species for the first time under laboratory conditions. Males were the active sex in the entire mating behavioural sequence involving approaching, courting and mounting females, and copulation. Copulation lasted for about 20 min. There was no significant difference in pre- courtship, courtship and mating durations between virgin and mated males. However, mated males were significantly more likely to perform courtship and to achieve mating than virgin ones. It is suggested that males learn from mating experience, which helps them achieve higher mating success. Both virgin and mated males tended to disrupt mating couples but could not separate them.

The leaf miner, Scaptomyza flava (Diptera: Drosophilidae), causes commercial losses to brassica crops, particularly in unsprayed Asian brassicas such as ‘Joi Choi’, ‘Pak Choi Sum’, and Chinese cabbage. The objective of this study was to assess the susceptibility of a larval/pupal parasitoid, Asobara persimilis (Hymenoptera: Braconidae), of this pest to insecticides registered for use on brassicas and to an insecticide, abamectin, used to control agromyzid leaf miners overseas, as a contribution to the development of an integrated pest management programme. Adults of A. persimilis were exposed to leaf discs dipped in solutions of field rates of abamectin and 13 insecticides registered for use on vegetable brassicas. Mortality after 24 h varied from 0% to 100%. In four replicated field trials in Pukekohe (South Auckland, New Zealand), Asian brassicas ‘Joi Choi’, ‘Pak Choi Sum’, and Chinese cabbage were sprayed with insecticides and numbers of leaves with leaf mines and fly damage were recorded from...

The European leafminer, Scaptomyza flava, is an important pest of brassicas, peas and gypsophila in New Zealand. The patterns of S. flava adult eclosion, mating and oviposition were determined in the laboratory. Most adults (97%) emerged in the photophase with maximum adult eclosion occurring between 2 and 3 h into the photophase. Mating took place exclusively in the photophase and peaked about 30 min after lights on. Both male and female S. flava mated more than once. Females started oviposition 3 days after emergence, and the fecundity (number of eggs laid) and fertility (number of eggs hatched) peaked between 5 and 10 days after emergence. The mean lifetime fecundity was 133.5±4.1 eggs with the fertility rate being 57% during the 40-day oviposition period.

The leaf miner, Scaptomyza flava (Diptera: Drosophilidae), can damage Asian brassicas. Methods of control are required that are compatible with biological control of the lepidopteran pests that also damage this crop. Laboratory bioassays compared the susceptibility of adult flies and first instar larvae in leaf mines to 12 insecticides registered for use on brassicas and the insecticide abamectin. The efficacy of seven insecticides were compared in two field trials with Joi Choi and Pak Choi, and the survival of a larval/pupal parasitoid, Asobara persimilis (Hymenoptera: Braconidae) was assessed. Adult and larval flies were susceptible to nine insecticides. In the field trials, abamectin, deltamethrin, endosulfan and fipronil gave good control of fly larvae. Parasitoids emerged in treatments where fly larvae survived to pupate, i.e. abamectin, endosulfan, maldison, spinosad and indoxacarb.

Mined leaves were sampled from unsprayed sites in Victoria to record the range of leafminers and their parasitoids. Three agromyzid leafminers, Liriomyza brassicae (Riley), Liriomyza chenopodii (Watt) and Chromatomyia syngenesiae Hardy, and one drosophilid leafminer, Scaptomyza flava (Fallen), were collected, along with 15 parasitoids, mainly Eulophidae. The most common parasitoids were Hemiptarsenus varicornis (Girault) (42.5%), Diglyphus isaea (Walker), 14.6%, Closterocerus mirabilis Edwards & La Salle (10.5%), and Opius cinerariae Fisher (8.5%). Most parasitoids were collected from two or more leafminer hosts. Weekly collections from Chinese cabbage (Brassica rapa var. pekinensis) infested with L. brassicae and S. flava, and beetroot (Beta vulgaris var. crassa) infested with L. chenopodii were made over two seasons at Knoxfield, Victoria to assess the relative impact of these parasitoids on agromyzid fly populations in crops. A further two parasitoid species were identified at low densities. Hemiptarsenus varicornis and D. isaea were the most numerous parasitoids collected in both crops. A different sampling method in the second year showed that O. cinerariae made up 25% of the sample from Chinese cabbage and was probably more common than estimated in the first season. Control exerted by local parasitoids was high, with 100% control of L. chenopodii reached in beets within 1–3 weeks of mines appearing and 100% control of L. brassicae within 6 weeks.

In New Zealand, the European leaf mining fly, Scaptomyza (Scaptomyza) flava (Fallen, 1823) (Diptera: Drosophilidae), is a pest of gypsophila and brassicas. Scaptomyza flava was first found in Levin (March 1964) and in 1965 was found in Hastings (March), Lincoln (July), and Nelson (December). By January 1968 it was found in Auckland and Gisborne. Voucher specimens in New Zealand show the species was correctly identified by the Commonwealth Institute of Entomology in 1965. However, this information was lost, and parasitoids of Agromyzidae were released (1969–71) to control what was initially assumed to be an agromyzid leaf miner of brassicas. The identity of the fly as S. flava was confirmed by Bock in 1988. In this study, six New Zealand insect collections were examined and field collections were made to confirm host associations, parasitism, and colonisation. Two parasitoids have been reared from S. flava in New Zealand, and overseas at least two other parasitoid species are known from this speci...

Plant-herbivore interactions have evolved in the presence of plant-colonizing microbes. These microbes can have important third-party effects on herbivore ecology, as exemplified by drosophilid flies that evolved from ancestors feeding on plant-associated microbes. Leaf-mining flies in the genus Scaptomyza, which is nested within the paraphyletic genus Drosophila, show strong associations with bacteria in the genus Pseudomonas, including Pseudomonas syringae. Adult females are capable of vectoring these bacteria between plants and larvae show a preference for feeding on P. syringae-infected leaves. Here we show that Scaptomyza flava larvae can also vector P. syringae to and from feeding sites, and that they not only feed more, but also develop faster on plants previously infected with P. syringae. Our genetic and physiological data show that P. syringae enhances S. flava feeding on infected plants at least in part by suppressing anti-herbivore defenses mediated by reactive oxygen species.

Herbivorous insects are extraordinarily successful. Half of the world’s extant insects and one quarter of all living metazoan species belong to herbivorous insect lineages (1, 2). Although feeding on living plant tissue is an evolutionarily difficult transition, herbivorous insect lineages are more diverse than their nonherbivorous relatives (3, 4). In PNAS, Goldman-Huertas et al. (5) present both the underlying genetic basis and the resulting physiological changes that led to the evolution of herbivory in the fly Scaptomyza flava (Fig. 1).

Herbivorous insects are among the most successful radiations of life. However, we know little about the processes underpinning the evolution of herbivory. We examined the evolution of herbivory in the fly, Scaptomyza flava, whose larvae are leaf miners on species of Brassicaceae, including the widely studied reference plant, Arabidopsis thaliana (Arabidopsis). Scaptomyza flava is phylogenetically nested within the paraphyletic genus Drosophila, and the whole genome sequences available for 12 species of Drosophila facilitated phylogenetic analysis and assembly of a transcriptome for S. flava. A time-calibrated phylogeny indicated that leaf mining in Scaptomyza evolved between 6 and 16 million years ago. Feeding assays showed that biosynthesis of glucosinolates, the major class of antiherbivore chemical defense compounds in mustard leaves, was upregulated by S. flava larval feeding. The presence of glucosinolates in wild-type (WT) Arabidopsis plants reduced S. flava larval weight gain and increased egg–adult development time relative to flies reared in glucosinolate knockout (GKO) plants. An analysis of gene expression differences in 5-day-old larvae reared on WT versus GKO plants showed a total of 341 transcripts that were differentially regulated by glucosinolate uptake in larval S. flava. Of these, approximately a third corresponded to homologs of Drosophila melanogaster genes associated with starvation, dietary toxin-, heat-, oxidation-, and aging-related stress. The upregulated transcripts exhibited elevated rates of protein evolution compared with unregulated transcripts. The remaining differentially regulated transcripts also contained a higher proportion of novel genes than the unregulated transcripts. Thus, the transition to herbivory in Scaptomyza appears to be coupled with the evolution of novel genes and the co-option of conserved stress-related genes.

Synthetic herbivore-induced plant volatiles (HIPVs) attract arthropod natural enemies showing potential for enhancing biological control. However, HIPVs can also affect the behavior of arthropod herbivores and possibly higher-order natural enemies, potentially complicating the use of HIPVs in biological control. The aim of our work is to understand the effects of one HIPV on the abundance of arthropods at three trophic levels. Of particular interest are effects on herbivores and enemies of natural enemies. A field experiment was carried out in turnip Brassica rapa L. (Brassicaceae) (cv. Green Globe). A randomized block design was used with a treatment of synthetic methyl salicylate (MeSA), and a control consisting of the crop alone. Yellow sticky traps were used for sampling aerial brassica pests, their natural enemies and fourth trophic-level natural enemies within the crop. Our results showed that the abundance of the diamondback moth parasitoid, Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae), the brassica leafmining pest Scaptomyza flava Fallén (Diptera: Drosophilidae), and the lacewing parasitoid, Anacharis zealandica Ashmead (Hymenoptera: Figitidae), increased significantly in the MeSA-treatment compared with the controls. Significantly more D. semiclausum females were attracted to MeSA than were males. However, it still remains unclear whether it is MeSA and/or volatiles produced by induced host plants that are attractive to the arthropods. These results are highly relevant to potential future application of HIPVs in pest management, as the attraction of arthropods within ‘untargeted’ trophic-levels may disrupt trophic cascades and challenges the ideas that the deployment of synthetic HIPVs in pest management may enhance biological control. Refereed/Peer-reviewed

Scaptomyza flava (Diptera Drosophilidae) known as European leaf miner has recently been identified as the pest species causing major damage to seed and other brassica crops grown in the South Island This pest is particularly damaging to hybrid Asian brassica seed crops but is also a major pest of seedlings of radish turnip and broccoli plants A larval/pupal parasitoid Asobara persimilis (Hymenoptera Braconidae) is an effective natural enemy of S flava at Pukekohe at certain times of the year A project funded by MAF Sustainable Farming Fund involves massrearing the parasitoids in Auckland and releasing them in unsprayed brassica crops in Canterbury and North Otago A total of 6550 pupae and 760 emerged adults were released over fortnightly periods at 46 sites from October 2010 to April 2011 The pupae included about 80 parasitised pupae and 20 that were unparasitised as a source of hosts for emerging parasitoids Overwintering surveys and further releases are planned for 2011/12 to try and establish this natural enemy as part of the ongoing development of IPM tools for seed forage and vegetable brassica crops grown in the South Island