Elevationally biased avian predation as a contributor to the spatial distribution of geometrid moth outbreaks in sub‐arctic mountain birch forest

1. Population dynamics and interactions that vary over a species' range are of particular importance in the context of latitudinal clines in biological diversity. Winter moth (Operophtera brumata) and autumnal moth (Epirrita autumnata) are two species of eruptive geometrids that vary widely in outbreak tendency over their range, which generally increases from south to north and with elevation. 2. The predation pressure on geometrid larvae and pupae over an elevational gradient was tested. The effects of background larval density and bird occupancy of monitoring nest boxes on predation rates were also tested. Predation on larvae was tested through exclusion treatments at 20 replicate stations over four elevations at one site, while pupae were set out to measure predation at two elevations at three sites. 3. Larval densities were reduced by bird predation at three lower elevations, but not at the highest elevation, and predation rates were 1.9 times higher at the lowest elevation than at the highest elevation. The rate of predation on larvae was not related to background larval density or nest box occupancy, although there were more eggs and chicks at the lowest elevation. There were no consistent differences in predation on pupae by elevation. 4. These results suggest that elevational variation in avian predation pressure on larvae may help to drive elevational differences in outbreak tendency, and that birds may play a more important role in geometrid population dynamics than the focus on invertebrate and soil predators of previous work would suggest.     

Efficient resolution of parentage in dogs by amplification of microsatellites

Parentage control has been performed for 15 litters from 12 different dog breeds by amplification of microsatellites. As it was possible to include all putative parents in all cases, they were solved by exclusion. Discrimination between parents/non-parents was made after genotyping of 6–9 microsatellite loci. In 12 of the cases all but one of the alleged fathers were excluded while in three cases it was unambiguously shown that superfecundation had taken place. Furthermore, one inclusion case concerning disputed maternity has been investigated. Maternity indices were calculated for 12 loci and probability of maternity was estimated to be 99-99%. These results testify that microsatellites can be applied very efficiently for resolution of parentage in dogs.     

Type-3 functional response in limnetic suspension-feeders,as demonstrated by in situ grazing rates

Field-measured grazing rates (ml/animal/d) of cladocerans (mostly daphniids) and diaptomids were assembled from various published studies and plotted as a function of corresponding phytoplankton concentration (μg l⁻¹ f.w.). Filtering rates of both zooplankton groups initially increased with seston concentration until maximal grazing rates were observed at approximately 4 × 10² and 1 × 10² μg l⁻¹ for cladocerans and copepods, respectively; at higher algal concentrations, filtering rates of both declined as a function of food concentration. The shape of these curves are most consistent with Holling's (1966) Type 3 functional response. We found little support for the Type 3 functional response in published laboratory studies of Daphnia; most investigators report either a Type 1 or Type 2 response. The one study in which the Type 3 response was observed involved experiments where animals were acclimated at low food concentrations for 24 h, whereas those studies associated with response Types 1 or 2 had acclimation periods of only 1 to 3 h. We therefore assembled relevant data from the literature to examine the effect of acclimation period on the feeding rates of Daphnia at low food concentrations. In the absence of any acclimation, animals filtered at extremely low rates. After 2 h of acclimation, however, filtering rates increased 4 to 5-fold but declined again with longer durations; after > 70 h of pre-conditioning, filtering rates were almost as low as they had been with no acclimation. We also found little support for the Type 3 functional response in published studies of copepods. The only study associated with a Type 3 response involved a marine copepod that had been subjected to a starvation period of 48 h; however, an analysis of the effects of acclimation period did not yield conclusive evidence that filtering rates of freshwater copepods (Diaptomus and Eudiaptomus) decrease significantly with acclimation duration. The low filtering rates associated with long acclimation periods in laboratory experiments appears to be a direct result of animals becoming emaciated from prolonged exposure to low food concentrations, a situation which renders them incapable of high filtering rates. This may explain the Type 3 functional response for field cladocerans, since zooplankton in food-limiting situations are constantly exposed to low food concentrations, and would therefore have low body carbon and consequently less energy to filter-feed. We cannot, however, use this to explain the Type 3 response for field diaptomids, since copepods in the laboratory did not appear to lose body carbon even after 72 h of feeding at very low food levels, and there was inconclusive evidence that either Diaptomus or Eudiaptomus decrease their filtering rates with acclimation period. Although Incipient Limiting Concentrations (ILC) for Daphnia ranged from 1 to 8.5 × 10³ μg 1⁻¹, more than half of these fell between 1 and 3 × 10³ μg l⁻¹, bracketing the value of 2.7 × 10² μg l⁻¹ for field cladocerans. There was, however, a great deal of variation in reported maximum ingestion rates (MIR), maximum filtering rates (MFR) and ILC values for Daphnia magna. ILC values from the few laboratory studies of freshwater copepods ranged between 0.5 to 2.8 × 10³ μg 1⁻¹, and was higher than the ILC value of approximately 0.2 × 10³ μg l⁻¹ calculated for field populations of D. minutus. Generally, there was considerable agreement among laboratory studies regarding the shape of grazing-rate and ingestion-rate curves when data were converted to similar units and presented on standardized scales.     

Lasioseius Fimetorum: a soil-dwelling predator of glasshouse pests?

Female lifespan and reproduction, in terms of numberof larvae produced, of the soil-dwelling predatorymite Lasioseius fimetorum Karg (Acari:Podocinidae) fed on mould mites (Tyrophagusputrescentiae [Schrank] [Acarina: Acaridae]) wereinvestigated by laboratory experiments at 20 °C,as were the mite's consumption rates of various prey.After a preoviposition period of 10.7 days, L.fimetorum produced progeny at a daily rate of 0.7.The oviposition period lasted 23.6 days and a total of19.4 progeny were produced per female. Females livedfor 38.6 days. Eggs of the Collembola Isotomurusspp. (Collembola: Isotomidae) were consumed in thelargest amount by L. fimetorum followed by mouldmite nymphs, larvae and pupae of thrips (Frankliniella occidentalis [Pergande] [Thysanoptera:Thripidae]), eggs of the Collembola Micrisotomaspp. (Collembola: Isotomidae), Isotomurus spp.nymphs and sciarid larvae (Bradysia pauperaTuomikoski and B. tritici (Coquillet) [Diptera:Sciaridae]). Immature drain flies (Psychoda spp.[Diptera: Psychodidae]) were not consumed by L.fimetorum. The suitability of L. fimetorum forbiological control of glasshouse pests withsoil-dwelling stages is discussed in comparison withanother predatory mite Hypoaspis miles Berlese(Acarina: Hypoaspididae).     

Implications of transgenic, insecticidal plants for insect and plant biodiversity

Genetically modified plants are widely grown predominantly in North America and to a lesser extent in Australia, Argentina and China but their regions of production are expected to spread soon beyond these limited areas also reaching Europe where great controversy over the application of gene technology in agriculture persists. Currently, several cultivars of eight major crop plants are commercially available including canola, corn, cotton, potato, soybean, sugar beet, tobacco and tomato, but many more plants with new and combined multiple traits are close to registration. While currently agronomic traits (herbicide resistance, insect resistance) dominate, traits conferring “quality” traits (altered oil compositions, protein and starch contents) will begin to dominate within the next years. However, economically the most promising future lies in the development and marketing of crop plants expressing pharmaceutical or “nutraceuticals” (functional foods), and plants that express a number of different genes. From this it is clear that future agricultural and, ultimately, also natural ecosystems will be challenged by the large-scale introduction of entirely novel genes and gene products in new combinations at high frequencies all of which will have unknown impacts on their associated complex of non-target organisms, i.e. all organisms that are not targeted by the insecticidal protein. In times of severe global decline of biodiversity, pro-active precaution is necessary and careful consideration of the likely expected effects of transgenic plants on biodiversity of plants and insects is mandatory.In this paper possible implications of non-target effects for insect and plant biodiversity are discussed and a case example of such non-target effects is presented. In a multiple year research project, tritrophic and bitrophic effects of transgenic corn, expressing the gene from Bacillus thuringiensis (Bt-corn) that codes for the high expression of an insecticidal toxin (Cry1Ab), on the natural enemy species, Chrysoperla carnea (the green lacewing), was investigated. In these laboratory trials, we found prey-mediated effects of transgenic Bt-corn causing significantly higher mortality of C. carnea larvae. In further laboratory trials, we confirmed that the route of exposure (fed directly or via a herbivorous prey) and the origin of the Bt (from transgenic plants or incorporated into artificial diet) strongly influenced the degree of mortality. In choice feeding trials where C. carnea could choose between Spodoptera littoralis fed transgenic Bt-corn and S. littoralis fed non-transgenic corn, larger instars showed a significant preference for S. littoralis fed non-transgenic corn while this was not the case when the choice was between Bt- and isogenic corn fed aphids. Field implications of these findings could be multifold but will be difficult to assess because they interfere in very intricate ways with complex ecosystem processes that we still know only very little about. The future challenge in pest management will be to explore how transgenic plants can be incorporated as safe and effective components of IPM systems and what gene technology can contribute to the needs of a modern sustainable agriculture that avoids or reduces adverse impacts on biodiversity? For mainly economically motivated resistance management purposes, constitutive high expression of Bt-toxins in transgenic plants is promoted seeking to kill almost 100% of all susceptible (and if possible heterozygote resistant) target pest insects. However, for pest management this is usually not necessary. Control at or below an established economic injury level is sufficient for most pests and cropping systems. It is proposed that partially or moderately resistant plants expressing quantitative rather than single gene traits and affecting the target pest sub-lethally may provide a more meaningful contribution of agricultural biotechnology to modern sustainable agriculture. Some examples of such plants produced through conventional breeding are presented. Non-target effects may be less severe allowing for better incorporation of these plants into IPM or biological control programs using multiple control strategies, thereby, also reducing selection pressure for pest resistance development.     

Status and Breeding Sites of Three Presumed Endangered Scottish Saproxylic Syrphids (Diptera, Syrphidae)

From 1987 to 1999 efforts were made to understand the status and breeding sites of three presumed endangered flies in Britain: Blera fallax (Linnaeus), Hammerschmidtia ferruginea (Fallén) and Callicera rufa Schummel (Diptera, Syrphidae). Historical data on flight periods, localities and breeding sites were collated from the literature and captured specimens in museums and other collections. Using these data, life cycles were investigated, and cited and other localities searched for adults and early stages. Looking for early stages was more productive than looking for adults. B. fallax is the most endangered. It has declined in abundance, is restricted to two localities and, in 1999, breeding sites were destroyed at one of these localities. In contrast C. rufa is widespread and not uncommon throughout northern Scotland. H. ferruginea is not as endangered as B. fallax but adverse factors such as habitat destruction affect most of its sites.     

Differential susceptibility to hydrogen sulfide-induced apoptosis between PHLDA1-overexpressing oral cancer cell lines and oral keratinocytes: Role of PHLDA1 as an apoptosis suppressor

Hydrogen sulfide (H₂S) is a novel gasotransmitter that plays multiple biological roles in various body systems. In addition to its endogenous production, H₂S is produced by bacteria colonizing digestive organs, including the oral cavity. H₂S was previously shown to enhance pro-apoptotic effects in cancer cell lines, although the mechanisms involved remain unclear. To properly assess the anti-cancer effects of H₂S, however, investigations of apoptotic effects in normal cells are also necessary. The aims of this study were (1) to compare the susceptibility to H₂S-induced apoptosis between the oral cancer cell line Ca9-22 and oral keratinocytes that were derived from healthy gingiva, and (2) to identify candidate genes involved in the induction of apoptosis by H₂S. The susceptibility to H₂S-induced apoptosis in Ca9-22 cells was significantly higher than that in keratinocytes. H₂S exposure in Ca9-22 cells, but not keratinocytes, enhanced the expression of pleckstrin homology-like domain, family A, member 1 (PHLDA1), which was identified through a differential display method. In addition, PHLDA1 expression increased during actinomycin D-induced apoptosis in Ca9-22 cells. Knockdown of PHLDA1 expression by small interfering RNA in Ca9-22 cells led to expression of active caspase 3, thus indicating apoptosis induction. The tongue cancer cell line SCC-25, which expresses PHLDA1 at a high level, showed similar effects. Our data indicate that H₂S is an anti-cancer compound that may contribute to the low incidence of oral cancer. Furthermore, we demonstrated the role of PHLDA1 as an apoptosis suppressor.     

Effect of temperature on woodwasp (Sirex noctilio F.) development and parasitism by the entomopathogenic nematode,Deladenus siricidicola

The woodwasp, Sirex noctilio, is a significant global pest of exotic pine plantations in the Southern Hemisphere and now threatens native pine forests in North America. Management in Australia relies on biocontrol using the nematode, Deladenus (= Beddingia) siricidicola (Bedding), which infects and sterilises females who then further disperse the nematode. This pest is spreading into warmer regions in Australia and South America and coupled with the threat of global climate change, there is uncertainty as to how increasing temperatures will affect the biocontrol program. S. noctilio within nematode-inoculated wood were reared at four temperatures (24, 25.3, 26.6 and 28 °C) to investigate the effects of elevated temperatures on wasp development (emergence time, sex ratio and size), development of eggs (number, size, and maturation) and infection by the nematode. At 24 °C, which reflects current field temperature, S. noctilio were bigger in size and all the eggs were normal and all were infected with nematodes. Modest rises in temperature reflecting climate change scenarios resulted in smaller sized S. noctilio, disrupted egg development and maturation, and lowered the nematode sterilisation rate in females. Reduced S. noctilio female body size and egg infection will likely compromise biocontrol by D. siricidicola in its current distribution, but disrupted egg development may act directly on the pest, limiting dispersal of S. noctilio into subtropical pine plantations and adaptation to climate change.     

Impact of Bacillus popilliae,Rickettsiella popilliae and entomopathogenic nematodes on a population of the scarabaeid,Cyclocephala hirta

Larvae of the scarabaeid, Cyclocephala hirta, are major pests of turfgrass in California. A field test was conducted against third instars that included the following treatments: untreated control; chemical insecticide (bendiocarb); milky disease bacterium (Bacillus popilliae); and entomopathogenic nematodes (Steinernema feltiae and Heterorhabditis bacteriophora). There were no significant differences in population reduction among the treatments, but the larval population in all plots showed a dramatic decline. The C. hirta population had a natural occurrence of milky disease and blue disease caused by Rickettsiella popilliae. The prevalence of blue disease during the course of the study averaged < 10% but that of milky disease averaged about 20%. More significantly, the soil from all treatment plots when bioassayed for B. popilliae showed that 67–90% of the larvae became infected with this bacterium. None of the larvae became infected with the blue disease organism. We conclude that B. popilliae was occurring in epizootic proportions in our field tests and was a significant mortality factor in causing the decline of the C. hirta population.     

Resorption of unemitted gametes in Lithognathus mormyrus (Sparidae,Teleostei): a possible synergic action of somatic and immune cells

The resorption of unemitted gametes during the post-spawning period of the male and female reproductive cycles in Lithognathus mormyrus was studied by histochemical, histological and cytological methods. The resorption of residual spermatozoa involved the phagocytotic activity of Sertoli cells bounding the seminiferous cysts of spermatozoa, and those associated with spermatogonia lining the lobular lumen. Spermatozoa remaining in the sperm duct were phagocytozed by the lining epithelial cells. Eosinophilic granulocytes and macrophages were identified in the vicinity of residual spermatozoa. The remnants of oocytes underwent an atretic phenomenon in which follicle cells were firstly involved, inducing a progressive fragmentation of the oocyte cytoplasm. Subsequently, eosinophilic granulocytes invaded oocyte degenerative areas and clung to the remaining vitelline inclusions ensuring their biotransformation into waste products (brown bodies). The analogy of the resorption processes of both male and female unemitted gametes during the post-spawning period of natural reproductive cycle, involving first the enveloping somatic cells and then immune cells, is emphasized.