Geographic parthenogenesis in the Australian arid zone: II. Climatic analysis of orthopteroid insects of the genera Warramaba and Sipyloidea

The Australian and zone harbours a surprising number of parthenogenetic organisms. including the well known case of the grasshopper Warramaba virgo. Less well known is the case of the stick insects of the Sipyloidea complex, which. despite its presence in the literature for over 15 years. has gone entirely unnoticed by workers in the field. We draw attention to the remarkable similarities between the evolution of parthenogenesis in Warramaba and Sipyloidea and analyse the geographic distributions of parthenogenetic and sexual forms with respect to six Climatic variables. We provide evidence that a combination of Climatic and vegetative barriers are responsible for the current distribution patterns in these taxa. Comparisons are also made with patterns of geographic parthenogenesis in lizards of the Heteronotia binoei complex. In general. there has been a strong tendency for parthenogenesis to originate via hybridization in the western part of the and zone with subsequent eastward spread throughout mulga woodlands and mallee shrublands where rainfall is both low and aseasonal. We propose that the hybridization events leading to parthenogenesis in these diverse taxa were driven by a common biogeographic process - that is, by range shifts associated with changes in aridity during the late Pleistocene.

Pacific damsel bug: Friend of foe?

Determining the diet of insects present in cotton should be among the first steps in any applied research program. Omnivorous species are particularly important as they have the potential to suppress pest populations through prey feeding, but also to cause economic damage to the crop through plant feeding.

Lectin-induced haemocyte inactivation in insects

Most multimeric lectins are adhesion molecules, promoting attachment and spreading on surface glycodeterminants. In addition, some lectins have counter-adhesion properties, detaching already spread cells which then acquire round or spindle-formed cell shapes. Since lectin-mediated adhesion and detachment is observed in haemocyte-like Drosophila cells, which have haemomucin as the major lectin-binding glycoprotein, the two opposite cell behaviours may be the result of lectin-mediated receptor rearrangements on the cell surface. To investigate oligomeric lectins as a possible extracellular driving force affecting cell shape changes, we examined lectin-mediated reactions in lepidopteran haemocytes after cytochalasin D-treatment and observed that while cell-spreading was dependent on F-actin, lectin-uptake was less dependent on F-actin. We propose a model of cell shape changes involving a dynamic balance between adhesion and uptake reactions. (C) 2004 Elsevier Ltd. All rights reserved.

Wolbachia-induced cytoplasmic incompatibility as a means for insect pest population control

Biological control is the purposeful introduction of parasites, predators, and pathogens to reduce or suppress pest populations. Wolbachia are inherited bacteria of arthropods that have recently attracted attention for their potential as new biocontrol agents. Wolbachia manipulate host reproduction by using several strategies, one of which is cytoplasmic incompatibility (CI) [Stouthamer, R., Breeuwer, J. A. J. & Hurst, G. D. D. (1999) Annu. Rev. Microbiol. 53,71-102]. We established Wolbachia-infected lines of the medfly Ceratitis capitata using the infected cherry fruit fly Rhagoletis cerasi as donor. Wolbachia induced complete CI in the novel host. Laboratory cage populations were completely suppressed by single releases of infected males, suggesting that Wolbachia-induced CI could be used as a novel environmentally friendly tool for the control of medfly populations. The results also encourage the introduction of Wolbachia into pest and vector species of economic and hygenic relevance to suppress or modify natural populations.

Spider ballooning in soybean and non-crop areas of southeast Queensland

Ballooning is a form of aerial movement practiced by most miniature and some adult spiders. Very few studies have investigated the composition and rate of spider ballooning in Australian agroecosystems. Water traps were used to compare ballooning rates in irrigated soybean crops and nearby non-crop areas in southeast Queensland over two summer seasons. The highest ballooning rate (14.8 spiders/m(2) per day) was recorded in a soybean field, non-crop areas (7.0 spiders/m(2) per day) and a dry land mungbean field (6.8 spiders/m(2) per day) having similar rates. Spider ballooning in soybean increased throughout the season and showed three peaks and intervening troughs. A similar pattern in ballooning peaks was observed in non-crop areas however the numbers were lower. Peaks in ballooning activity where synchronised across habitat types and some spider groups. Composition of the ballooning fauna was different from that of the ground-dwelling fauna, some families being present in both. Ballooning is an important behaviour in terms of population dynamics for a number of spider groups in soybean and the implications for pest control are discussed. (C) 2004 Elsevier BN. All rights reserved.

Experimental analysis of the influence of pest management practice on the efficacy of an endemic arthropod natural enemy complex of the diamondback moth.

Maximizing the contribution of endemic natural enemies to integrated pest management (IPM) programs requires a detailed knowledge of their interactions with the target pest. This experimental field study evaluated the impact of the endemic natural enemy complex of Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) on pest populations in commercial cabbage crops in southeastern Queensland, Australia. Management data were used to score pest management practices at experimental sites on independent Brassica farms practicing a range of pest management strategies, and mechanical methods of natural enemy exclusion were used to assess the impact of natural enemies on introduced cohorts of P. xylostella at each site. Natural enemy impact was greatest at sites adopting IPM and least at sites practicing conventional pest management strategies. At IPM sites, the contribution of natural enemies to P. xylostella mortality permitted the cultivation of marketable crops with no yield loss but with a substantial reduction in insecticide inputs. Three species of larval parasitoids (Diadegma semiclausum Hellen [Hymenoptera: Ichneumonidae], Apanteles ippeus Nixon [Hymenoptera: Braconidae], and Oomyzus sokolowskii Kurdjumov [Hymenoptera: Eulophidae]) and one species of pupal parasitoid Diadromus collaris Gravenhorst (Hymenoptera: Ichneumonidae) attacked immature P. xylostella. The most abundant groups of predatory arthropods caught in pitfall traps were Araneae (Lycosidae) > Coleoptera (Carabidae, Coccinelidae, Staphylinidae) > Neuroptera (Chrysopidae) > Formicidae, whereas on crop foliage Araneae (Clubionidae, Oxyopidae) > Coleoptera (Coccinelidae) > Neuroptera (Chrysopidae) were most common. The abundance and diversity of natural enemies was greatest at sites that adopted IPM, correlating greater P. xylostella mortality at these sites. The efficacy of the natural enemy complex to pest mortality under different pest management regimes and appropriate strategies to optimize this important natural resource are discussed.

Discrimination among host plants (Leucaena species and accessions) by the psyllid pest Heteropsylla cubana and implications for understanding resistance

1 The herbivorous bug Heteropsylla cubana Crawford (Homoptera: Psyllidae) is a pest of the cattle fodder crop Leucaena (Leguminosae: Mimosoideae). The interaction between the psyllid and three varieties of its Leucaena host plant was investigated in relation to the apparent resistance of some Leucaena varieties (Leucaena leucocephala, Leucaena pallida and their hybrids) to attack. 2 Field trials demonstrated that adult psyllids distinguished among the different varieties of Leucaena over a distance, and were attracted to L. leucocephala in significantly higher numbers than to L. pallida or to the hybrid. Pesticide treatment increased the attractiveness of Leucaena plants, even of those deemed to be psyllid resistant. Numbers of psyllid eggs and nymphs, sampled in the field, reflect the arrival rates of adults at the three plant varieties. 3 Wavelength reflectance data of the three Leucaena varieties were not significantly different from one another, suggesting that psyllids cannot discriminate among the three plants using brightness or wavelength cues. There was a differential release of caryophyllene among the three varieties. Release of caryophyllene in L. leucocephala and the hybrid appeared to be influenced by environmental conditions. 4 Experiments demonstrated that caryophyllene (at least on its own) did not influence the behaviour of leucaena psyllids in relation to leucaena plants. 5 The results suggest that host plant volatiles cannot be dismissed as significant in the interaction between the leucaena psyllid and its Leucaena host plants. Further avenues for investigation are recommended and these are related to novel ways of understanding resistance in insect plant inter-relationships.

Genetic differentiation in Scottish populations of the pine beauty moth, Panolis flammea (Lepidoptera : Noctuidae)

Pine beauty moth, Panolis flammea (Denis & Schiffermuller), is a recent but persistent pest of lodgepole pine plantations in Scotland, but exists naturally at low levels within remnants and plantations of Scots pine. To test whether separate host races occur in lodgepole and Scots pine stands and to examine colonization dynamics, allozyme, randomly amplified polymorphic DNA (RAPD) and mitochondrial variation were screened within a range of Scottish samples. RAPD analysis indicated limited long distance dispersal (F-ST=0.099), and significant isolation by distance (P < 0.05); but that colonization between more proximate populations was often variable, from extensive to limited exchange. When compared with material from Germany, Scottish samples were found to be more diverse and significantly differentiated for all markers. For mtDNA, two highly divergent groups of haplotypes were evident, one group contained both German and Scottish samples and the other was predominantly Scottish. No genetic differentiation was evident between P. flammea populations sampled from different hosts, and no diversity bottleneck was observed in the lodgepole group. Indeed, lodgepole stands appear to have been colonized on multiple occasions from Scots pine sources and neighbouring populations on different hosts are close to panmixia.

The human papillomavirus type 16 E7 protein binds human interferon regulatory factor-9 via a novel PEST domain required for transformation

It is critical that viruses are able to avoid the antiviral activities of interferon (IFN). We have shown previously that the human papillomavirus (HPV) is able to avoid IFN-alpha via interaction of the HPV-16 E7 protein with IFN regulatory factor-9 (IRF-9). Here, we investigated the details of the interaction using HPV-16 E7 peptide mapping to show that IRF-9 binds HPV-16 E7 in a domain encompassing amino acids 25-36. A closer examination of this region indicates this is a novel proline, glutamate, serine, and threonine-rich (PEST) domain, with a PEST score of 8.74. We have also mapped the region of interaction within IRF-9 and found that amino acids 354-393 play an important role in binding to HPV-16 E7. This region of IRF-9 encompasses the IRF association domain (IAD), a region important for protein-protein interaction central to IRF function. Finally, we used alanine-scanning mutagenesis to determine if E7-IRF-9 interaction was important for E7-mediated cellular transformation and found that the HPV-16 E7 mutants Y25A, E26A, S31A, S32A, and E35A, but not L28A and N29A, caused loss of transformation ability. Preliminary data suggest loss of IRF-9 interaction with E7 mutants correlated with transformation. Our work suggests E7- IRF- 9 interaction is important for the transforming ability of HPV-16 E7 and that HPV-16 E7 may interact with other IRF proteins that have IAD domains.

Comment on "On the regulation of populations of mammals, birds, fish, and insects" II

Sibly et at. (Reports, 22 July 2005, p. 607) recently estimated the relationship between population size and growth rate for 1780 time series of various species. I explain why some aspects of their analysis are questionable and, therefore, why their results and estimation procedure should be used with care.

Microsatellite markers for the pest fruit fly, Bactrocera papayae (Diptera : Tephritidae) and other Bactrocera species

The dorsalis complex contains some of the most economically important fruit fly pests of the Asia-Pacific regions, including Bactrocera dorsalis, Bactrocera papayae and Bactrocera carambolae. These species are morphologically indistinct and genetically very similar. We describe the development of 12 microsatellite markers isolated from a representative of the dorsalis complex, B. papayae. We show the potential utility of the B. papayae microsatellites and a set of microsatellites isolated from Bactrocera tryoni as population and species markers for the dorsalis complex.

Temporal variation in arthropod sampling effectiveness: the case for using the beat sheet method in cotton

Predatory insects and spiders are key elements of integrated pest management (IPM) programmes in agricultural crops such as cotton. Management decisions in IPM programmes should to be based on a reliable and efficient method for counting both predators and pests. Knowledge of the temporal constraints that influence sampling is required because arthropod abundance estimates are likely to vary over a growing season and within a day. Few studies have adequately quantified this effect using the beat sheet, a potentially important sampling method. We compared the commonly used methods of suction and visual sampling to the beat sheet, with reference to an absolute cage clamp method for determining the abundance of various arthropod taxa over 5 weeks. There were significantly more entomophagous arthropods recorded using the beat sheet and cage clamp methods than by using suction or visual sampling, and these differences were more pronounced as the plants grew. In a second trial, relative estimates of entomophagous and phytophagous arthropod abundance were made using beat sheet samples collected over a day. Beat sheet estimates of the abundance of only eight of the 43 taxa examined were found to vary significantly over a day. Beat sheet sampling is recommended in further studies of arthropod abundance in cotton, but researchers and pest management advisors should bear in mind the time of season and time of day effects.

Do predators aggregate in response to pest density in agroecosystems? Assessing within-field spatial patterns

1. The spatial heterogeneity of predator populations is an important component of ecological theories pertaining to predator-prey dynamics. Most studies within agricultural fields show spatial correlation (positive or negative) between mean predator numbers and prey abundance across a whole field over time but generally ignore the within-field spatial dimension. We used explicit spatial mapping to determine if generalist predators aggregated within a soybean field, the size of these aggregations and if predator aggregation was associated with pest aggregation, plant damage and predation rate. 2. The study was conducted at Gatton in the Lockyer Valley, 90 km west of Brisbane, Australia. Intensive sampling grids were used to investigate within-field spatial patterns. The first row of each grid was located in a lucerne field (10 m from interface) and the remaining rows were in an adjacent soybean field. At each point on the grid the abundance of foliage-dwelling and ground-dwelling pests and predators was measured, predation rates [using sentinel Helicoverpa armigera (Hubner) egg cards] and plant damage were estimated. Eight grids were sampled across two summer cropping seasons (2000/01, 2001/02). 3. Predators exhibited strong spatial patterning with regions of high and low abundance and activity within what are considered to be uniform soybean fields. Ground-dwelling and foliage-dwelling predators were often aggregated in patches approximately 40 m across. 4. Lycosidae (wolf spiders) displayed aggregation and were consistently more abundant within the lucerne, with a decreasing trap catch with distance from the lucrene/soybean interface. This trend was consistent between subsequent grids in a single field and between fields. 5. The large amount of spatial variability in within-field arthropod abundance (pests and predators) and activity (egg predation and plant damage) indicates that whole field averages were misleading. This result has serious implications for sampling of arthropod abundance and pest management decision-making based on scouting data. 6. There was a great deal of temporal change in the significant spatial patterns observed within a field at each sampling time point during a single season. Predator and pest aggregations observed in these fields were generally not stable for the entire season. 7. Predator aggregation did not correlate consistently with pest aggregation, plant damage or predation rate. Spatial patterns in predator abundance were not associated consistently with any single parameter measured. The most consistent positive association was between foliage-dwelling predators and pests (significant in four of seven grids). Inferring associations between predators and prey based on an intensive one-off sampling grid is difficult, due to the temporal variability in the abundance of each group. 8. Synthesis and applications. This study demonstrated that generalist predator populations are rarely distributed randomly and field edges and adjacent crops can have an influence on within-field predator abundance. This must be considered when estimating arthropod (pest and predator) abundance from a set of samples taken at random locations within a field.

In vitro production of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus

Naturally occurring insect viruses are a promising means of intentionally causing disease in insects but they do not compete successfully with synthetic chemicals in the commercial marketplace. Furthermore, their use for pest control is still restricted. One factor preventing the development of baculoviruses as effective biopesticides is concern over the production issue. In vitro instability during propagation of these viruses in suspension cells is the major limitation to the in vitro production ofbaculoviruses in cell cultures. In this study, an isolated baculovirus (HaSNPV) was cultivated using serial passaging in a suspension cell culture. The results show a reduction in the occlusion body production during six passages, due to the passage effect. However the purification of an HaSNPV clone suggested better stability. A simple method used in this work for the serial passaging of this virus is discussed.