A study of the parasitoid complex of the European fir budworm, Choristoneura murinana (Lepidoptera: Tortricidae), and its relevance for biological control of related hosts

The parasitoid complex and apparent parasitism of Choristoneura murinana Hübner were investigated in relation to the relative abundance of budworm larvae at several sites in Europe. A single outbreak population was sampled, while other sites supported varying but much lower host population abundance. Sampling at Sion in Switzerland from 1984-89, indicated that the species richness of the parasitoid complex was correlated with relative host abundance and in general more polyphagous parasitoids were represented in sites with greater budworm abundance. Of the specialized parasitoids, Apanteles murinanae Čapek & Zwölfer (Hymenoptera: Braconidae) was dominant in less abundant host populations and both Cephaloglypta murinanae (Bauer) and Dirophanes maculicornis (Stephens) (Hymenoptera: Ichneumonidae) were supported only at greater budworm abundance. These findings are discussed in relation to the use of Choristoneura murinana parasitoids in the biological control of native Choristoneura spp. pests in other continent

Evidence for the occurrence of sibling species in Eubazus spp. (Hymenoptera: Braconidae), parasitoids of Pissodes spp. weevils (Coleoptera: Curculionidae)

Comparative studies were made on three presumed sibling species of the genus Eubazus, parasitoids of European Pissodes spp. weevils, to clarify their taxonomy and define diagnostic characters. Several populations of E. semirugosus (Nees), E. robustus (Ratzeburg) and Eubazus sp. were compared with respect to their morphology (mainly through morphometric analyses), fecundity, isoenzyme patterns and host preference. Crosses were made to assess the genetic and behavioural compatibility of the populations. In addition, the North American E. crassigaster (Provancher), a parasitoid of Pissodes strobi (Peck), was compared to E. semirugosus, a species selected for introduction against P. strobi in Canada. The ratio of the length of the ovipositor sheath to the fore wing length was the most discriminating morphometric variable, but discriminant analyses including several measurements were needed to completely separate European species. A canonical discriminant function provided a total separation between males of E. crassigaster and E. semirugosus, but not between females. Eubazus crassigaster and E. semirugosus were totally separated by the banding pattern of the enzyme phosphogluconate dehydrogenase whereas hexokinase and esterase provided a diagnostic separation between Eubazus sp. and E. robustus. Eubazus sp. differed from all the other species by having a greater number of ovarioles and, consequently, a higher potential fecundity. In a two-choice oviposition test, E. semirugosus and Eubazus sp. showed a significant preference for their natural host, P. castaneus De Geer and P. piceae (Illiger), respectively. A similar test made with their progenies reared under standard conditions showed that the difference in host preference was genetically fixed. Males and females of different species did not mate readily, in contrast to individuals from the same species. All attempts to interbreed E. robustus and Eubazus sp. failed, but a few crosses between E. semirugosus and the two other European species produced fertile offspring. These observations strongly suggest that the complex of Eubazus spp. parasitoids attacking Pissodes spp. in Europe is composed of at least three sibling species, two of which appear to have specialized on distinct host species that occupy exclusive microhabitat

Quantifying the impact of insect predators and parasitoids on populations of the apple ermine moth, Yponomeuta malinellus (Lepidoptera: Yponomeutidae), in Europe

Life tables were developed to assess the significance of natural enemies on the dynamics of apple ermine moth, Yponomeuta malinellus Zeller, in southwestern Germany and to select parasitoid species for use in the biological control of this pest in Canada. During the study from 1993 to 1995 the abundance of Y. malinellus varied from 1.5 to 4.3 tents per 100 leaf clusters indicating that this was a non-outbreak population. From the life tables it was evident that the impact of egg predators accounted for 25-43% of the total generational mortality of Y. malinellus, more than any other known mortality factor. Percent parasitism varied from 18 to 30%, but the impact of parasitoids in relation to the total generational mortality of Y. malinellus from the life tables was remarkably constant at 11-14%. The loss of potential fecundity had an important influence on the generational mortality of Y. malinellus, but declined from 27% to 15% over the course of this study. This decline corresponded with a rise in the net rate of increase R0 from 1.35 in 1993 to 6.8 in 1995, despite the impact of insect predators and parasitoids on the generational mortality. Yponomeuta malinellus was attacked by five different obligate primary parasitoids, a single obligate hyperparasitoid, and three facultative hyperparasitoids. Of these, the oligophagous egg-larval parasitoid Ageniaspis fuscicollis Dalman (Encyrtidae) and the oligophagous larval-pupal and pupal parasitoid Herpestomus brunnicornis Gravenhorst (Ichneumonidae) were selected as potential biological control agents for Canada due to a minimal degree of interspecific competitio

Comparative developmental biology of populations of three European and one North American Eubazus spp. (Hymenoptera: Braconidae), parasitoids of Pissodes spp. weevils (Coleoptera: Curculionidae)

Observations were made on the developmental responses of the North American braconid species, Eubazus crassigaster, a parasitoid of the white pine weevil, Pissoles strobi, and three European congeneric species, E. semirugosus, E. robustus, and Eubazus sp. Several populations of Eubazus spp. were compared in their phenology in the laboratory and under natural conditions. When reared in the laboratory on non-diapausing Pissodes castaneus, mountain populations of E. semirugosus and E. robustus entered into an obligatory diapause in the host larva, whereas all the other populations tested developed continuously. Diapausing larvae continued their development only after having experienced at least three months at 2°C. Non-diapausing populations of Eubazus spp. significantly differed in the duration of pre-imaginal development, with E. semirugosus being the fastest developing species and E. robustus the slowest. Outdoor rearings of Eubazus spp. on P. castaneus showed that E. crassigaster, Eubazus sp. and the lowland biotype of E. semirugosus emerged in the year of oviposition if this occurred early enough to allow parasitoid development. In contrast, a majority of E. robustus individuals overwintered in the host larvae, regardless of the oviposition date. The diapausing, mountain biotype of E. semirugosus is considered as the most promising candidate for control of P. strobi in Canada, because it is likely to be better adapted to the life cycle of the target host than the other Eubazus spp., including the native E. crassigaste

Impact and oviposition behaviour of Ageniaspis fuscicollis (Hymenoptera: Encyrtidae), a polyembryonic parasitoid of the apple ermine moth, Yponomeuta malinellus (Lepidoptera: Yponomeutidae)

The distribution and extent of parasitism of the apple ermine moth Yponomeuta malinellus Zeller by the polyembyronic encyrtid parasitoid Ageniaspis fuscicollis (Dalman) were examined in a three year field study and related to oviposition behaviour in the laboratory. Ageniaspis fuscicollis attacks egg batches of its host and kills the final instar larvae, which feed gregariously from within tents. Host population densities in the field were low, from 1.5 to 2.2 tents per 100 leaf clusters, and parasitism increased from 7.8% to 18% over the three year period. Parasitism was independent of host density at the whole tree scale, but at the individual tent scale, the probability of a tent containing parasitized host larvae increased and percent parasitism decreased with the number of host larvae per tent. Observations on the oviposition behaviour of A. fuscicollis in the laboratory revealed that parasitoids distributed their eggs randomly within host egg batches. On average, they spent almost two hours on an egg batch and laid 44% of their egg load of 132 eggs into the first egg batch visited, leading to a mean of 1.4 eggs laid per host egg through frequent self-superparasitism of hosts. The percentage of eggs receiving one or more ovipositions was independent of the size of an egg batch, contradicting our field observations of inverse density dependence. Factors that might account for the differences in rates of parasitism and attack distributions between laboratory and field data are discusse

Anthropogenic alteration of nutrient supply increases the global freshwater carbon sink

Lakes have a disproportionate effect on the global carbon (C) cycle relative to their area, mediating C transfer from land to atmosphere, and burying organic-C in their sediments. The magnitude and temporal variability of C burial is, however, poorly constrained, and the degree to which humans have influenced lake C cycling through landscape alteration has not been systematically assessed. Here, we report global and biome specific trajectories of lake C sequestration based on 516 lakes and show that some lake C burial rates (i.e., those in tropical forest and grassland biomes) have quadrupled over the last 100 years. Global lake C-sequestration (~0.12 Pg year−1) has increased by ~72 Tg year−1 since 1900, offsetting 20% of annual CO2 freshwater emissions rising to ~30% if reservoirs are included and contributing to the residual continental C sink. Nutrient availability explains ~70% of the observed increase, while rising temperatures have a minimal effect

Crustal carbonate build-up as a driver for Earth’s oxygenation

Oxygenation of Earth’s atmosphere and oceans played a pivotal role in the evolution of the surface environment and life. It is thought that the rise in oxygen over Earth’s history was driven by an increasing availability of the photosynthetic limiting nutrient phosphate combined with declining oxygen-consuming inputs from the mantle and crust. However, it has been difficult to assess whether these processes alone can explain Earth’s oxygenation history. Here we develop a theoretical framework for the long-term global oxygen, phosphorus and carbon cycles, incorporating potential trajectories for the emergence of continents, the degassing of mantle volatiles and the resulting increase in the size of the crustal carbonate reservoir. We find that we can adequately simulate the Earth’s oxygenation trajectory in both the atmosphere and oceans, alongside reasonable reconstructions of planetary temperature, atmospheric carbon dioxide concentration, phosphorus burial records and carbon isotope ratios. Importantly, this is only possible when we include the accumulation of carbonates in the crust, which permits ever-increasing carbon recycling rates through weathering and degassing. This carbonate build-up is a missing factor in models of Earth’s coupled climate, nutrient and oxygen evolution and is important for reconstructing Earth’s history and potential exoplanet biogeochemistry

Polytypism and polysomatism in mixed-layer chalcogenides: characterization of PbBi(4)Te(4)S(3) and inferences for ordered phases in the aleksite series

Bi-Pb-chalcogenides of the aleksite series represent homologous mixed-layer compounds derived from tetradymite (Bi₂Te₂S). Considering tetradymite as composed of five-atom (Bi₂Te₂S) layers, the named minerals of the aleksite homologous series, aleksite (PbBi₂Te₂S₂) and saddlebackite, (Pb₂Bi₂Te₂S₃) have been considered as phases formed by regular stacking of longer seven- and nine-atom layers. High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) imaging of thinned foils prepared in-situ on domains deemed homogeneous from electron probe microanalysis, STEM energy-dispersive X-ray spectrometry (EDS) element mapping and fast Fourier transforms (FFTs) from the images offer new insights into these structures. The hitherto-unnamed phase, PbBi₄Te₄S₃, previously interpreted as regular intergrowths of five- and seven-atom layers, is characterized in terms of regular repeats of five- and seven-atom layers over distances of at least 350 nm, defining the (57), or 24H polytype. Imaging of other domains in the same lamella with identical composition at the electron microprobe scale reveals the presence of two additional polytypes: (5559), or 48H; and (557.559) or 72H. Unit cell dimensions for all three polytypes of PbBi₄Te₄S₃ can be both measured and predicted from the HAADF STEM imaging and FFTs. STEM EDS mapping of each polytype confirm the internal structure of each layer. Lead and S occur within the centre of the layers, i.e., Te–Bi–S–Pb–S–Bi–Te in the seven-atom layer, Te–Bi–S–Pb–S–Pb–S–Bi–Te in the nine-atom layer, and so on. Polytypism is an intrinsic feature of the aleksite series, with each named mineral or unnamed phase, except the simple five-atom layer, defined by several alternative stacking sequences of different length, readily explaining the differing c values given in previous work. Homology is defined in terms of layer width and the stacking arrangement of those layers. Coherent structures of the same composition need not only be built of layers of adjacent size (i.e., five- and seven-atom layers) but, as exemplified by the (5559) polytype, may also contain non-adjacent layers, a finding not anticipated in previous work. New polysomes remain to be discovered in nature and each potentially exists as multiple polytypes. The present study further emphasizes the utility of HAADF STEM imaging and atomic-scale STEM EDS element mapping as an optimal tool for tracking stacking sequences and characterising structures in mixed-layer compounds.Nigel J. Cook, Cristiana L. Ciobanu, Wenyuan Liu, Ashley Slattery, Benjamin P. Wade, Stuart J. Mills, and Christopher J. Stanle

The mediating role of parenting in the associations between household chaos and children’s representations of family dysfunction

Children’s drawings are thought to reflect their mental representations of self and their interpersonal relations within families. Household chaos is believed to disrupt key proximal processes related to optimal development. The present study examines the mediating role of parenting behaviors in the relations between two measures of household chaos, instability and disorganization, and how they may be evidenced in children’s representations of family dysfunction as derived from their drawings. The sample (N= 962) is from a longitudinal study of rural poverty exploring the ways in which child, family, and contextual factors shape development over time. Findings reveal that, after controlling for numerous factors including child and primary caregiver covariates, there were significant indirect effects from cumulative family disorganization, but not cumulative family instability, on children’s representation of family dysfunction through parenting behaviors. Results suggest that the proximal effects of daily disorganization outweigh the effects of periodic instability overtime

Anthropogenic alteration of nutrient supply increases the global freshwater carbon sink

Lakes have a disproportionate effect on the global carbon (C) cycle relative to their area, mediating C transfer from land to atmosphere, and burying organic-C in their sediments. The magnitude and temporal variability of C burial is, however, poorly constrained, and the degree to which humans have influenced lake C cycling through landscape alteration has not been systematically assessed. Here, we report global and biome specific trajectories of lake C sequestration based on 516 lakes and show that some lake C burial rates (i.e., those in tropical forest and grassland biomes) have quadrupled over the last 100 years. Global lake C-sequestration (~0.12 Pg year-1) has increased by ~72 Tg year-1 since 1900, offsetting 20% of annual CO2 freshwater emissions rising to ~30% if reservoirs are included and contributing to the residual continental C sink. Nutrient availability explains ~70% of the observed increase, while rising temperatures have a minimal effect