Interactions among intraspecific competition, emergence patterns, and host selection behaviour in Ips pini (Coleoptera: Scolytinae)

Abstract.  1. Variations in developmental conditions of bark beetles, particularly intraspecific competition, can induce morphological and physiological modifications in the offspring. It is hypothesised that intraspecific competition could also affect host selection behaviour. Such behavioural changes might be manifested in response to host (alpha-pinene) or beetle (verbenone) compounds.
2.  Ips pini were bred at different densities. The offspring were measured for size, weight, and lipid concentration, and then subjected to tunnelling bioassays in agar media amended with varying amounts of alpha-pinene or verbenone.
3. High parental colonisation densities reduced emergence time of parents and offspring. Increasing colonisation density and emergence time had a negative influence on offspring vigour, resulting in a reduction of the distance tunnelled by the beetles.
4. Both alpha-pinene and verbenone were repellent. Surprisingly, verbenone was also toxic at high concentrations, with its effect being greater on beetles arising from high densities. The repellent effect of these compounds did not vary according to colonisation density, but for both compounds, at a 1.5 mg g^–1 concentration, it increased with emergence time.
5. The consequences of varying vigour and behaviour in relation to developmental conditions and emergence patterns on population dynamics of I. pini are discussed.     

Foliar architecture of vanilloid orchids: insights into the evolution of reticulate leaf venation in monocotyledons

Leaves of representative taxa within the vanilloid clade of Orchidaceae were cleared and their venation patterns studied. Within subtribe Pogoniinae, Isotria and Pogonia exhibit a prominent reticulate venation pattern, although only Pogonia ophioglossoides is characterized by free vein endings. Within subtribe Vanillinae, all species of Epistephium , as well as the New Caledonian endemics, Eriaxis rigida and Clematepistephium smilacifolium , have reticulate-veined leaves that are characterized by numerous free vein endings. Leaves of most species of Vanilla exhibit a parallel-veined pattern stereotypical of monocots, although branched secondaries with free endings were observed in V. africana. Most members of subtribe Galeolinae are 'saprophytes' with reduced bract-like leaves. Vascular bundles enter these leaf-homologues in a parallel manner, but quickly ram+ throughout the tissue in an irregular manner. Leaf venation is used to hypothesize patterns of generic relationships within the vanilloid clade. Molecular evidence for phylogenetic relationships among angiosperms indicates that reticulate leaf venation has arisen independently in several unrelated monocot families, including the vanilloid Orchidaceae, perhaps by a similar evolutionary scenario.     

Mosquito density, biting rate and cage size effects on repellent tests

Mosquito biting rates and the mean duration of protection (in hours) from bites (MDPB) of Aedes aegypti and Anopheles quadrimaculatus , using the repellent 'deet' ( N , N -diethyl-3-methylbenzamide) on a 50 cm² area of healthy human skin, were observed in small (27 l), medium (≈65 l) and large (125 l) cages containing low, medium or high densities of mosquitoes: respectively, 640, 128 or 49 cm³ of cage volume per female. At the initial treatment rate of ≈ 0.4 μl/cm² (1 ml of 25% deet in ethanol on 650 cm² of skin), the MDPB for deet against Ae. aegypti ranged from 4.5 to 6.5 h and was significantly less (5.0 ± 0.8 h) in large cages compared with medium (6.2 ± 0.9 h) and small (6.2 ± 0.8 h) cages, regardless of the density. Against An. quadrimaculatus the MDPB for deet 0.4 μl/cm² was 1.5–8.0 h, less in small (3.7 ± 2.3 h) and large (2.2 ± 1.1 h) cages at medium (3.7 ± 2.3 h) and high (2.5 ± 1.7 h) mosquito densities, and was longest in medium cages (6.2 ± 2.6 h) at low mosquito densities (5.8 ± 2.8 h). With equinoxial photoperiodicity (light on 06.00–18.00 hours) the biting rate was influenced by the time of observation (08.00, 12.00, 16.00 hours) for Ae. aegypti but not for An. quadrimaculatus. For both species, the biting rate was inversely proportional to mosquito density and the MDPB. The shortest MDPBs were obtained in large cages with high densities of mosquitoes and longest protection times occurred in medium sized cages with low mosquito densities.     

Characterisation of Cydia pomonella granulovirus from codling moths in a laboratory colony and in orchards of British Columbia*

Sequence analyses indicate that a granulovirus isolated from a laboratory colony of codling moth in British Columbia, Canada is identical or very similar to the Mexican isolate of Cydia pomonella granulovirus (CpGV-M). In addition to codling moth, the vims was found to cause mortality of secondary leafroller pests of North American orchards, including the fruit tree leafroller and the obliquebanded leafroller. A survey in apple growing regions of British Columbia indicates that 23% of the wild population of codling moth larvae carry CpGV.     

Bone Load Estimation for the Proximal Femur Using Single Energy Quantitative CT Data

A density-based load estimation method was applied to determine femoral load patterns. Two-dimensional finite element models were constructed using single energy quantitative computed tomography (QCT) data from two femora. Basic load cases included parabolic pressure joint loads and constant tractions on the greater trochanter. An optimization procedure adjusted magnitudes of the basic load cases, such that the applied mechanical stimulus approached the ideal stimulus throughout each model. Dominant estimated load directions were generally consistent with published experimental data for gait. Other estimated loads suggested that loads at extreme joint orientations may be important to maintenance of bone structure. Remodeling simulations with the estimated loads produced density distributions qualitatively similar to the QCT data sets. Average nodal density errors between QCT data and predictions were 0.24 g/cm(3) and 0.28 g/cm(3). The results indicate that density-based load estimation could improve understanding of loading patterns on bones.     

The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. I. Trophic relationships with special reference to the role of Neomysis integer

• 1 Hickling Broad, a shallow, brackish lake in England, changed from dominance by submerged aquatic plants to dominance by phytoplankton in the 1970s. These changes were ascribed to the effects of guanotrophicatioh by black-headed gulls, and increased salinity which together resulted in fish kills caused by a toxic alga, Prymnesium parvum. A mysid, Neomysis integer, was believed to be important in switching the system to plankton dominance through its presumed selective feeding on Cladocera and increasing population size as fish predation decreased.
• 2 Studies on laboratory predation rates of the mysid on Cladocera and on the population dynamics, predation rates and diet of the mysid and the populations of the major zooplankter, Eurytemora affinis in the Broad in the 1980s, have shown that the former explanations were incomplete. The mysid could have markedly reduced the cladoceran community, for it has potentially high predation rates, but Cladocera were probably lost through salinization. Neomysis feeds efficiently on Eurytentora affinis, but the latter reproduces rapidly and its populations are unlikely to be controlled by mysid predation. Nauplii and small copepodites are selectively taken. Alternative and probably major food sources for the mysid are periphyton and benthic algae and detritus.
• 3 Roach and bream readily take the mysid but the present fish stock in the Broad is very low and can now exert minimal pressure on the mysid population. An invertebrate predator on the mysid, Palaemometes varians, is also unlikely to have major effects. The former model of the operation of the Broad's ecosystem needs reconsideration in view of the findings.

     

The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. II. Long-term trends in water chemistry and ecology and their implications for restoration of the lake

• 1 Hickling Broad underwent major changes from a clear water, charophyte-dominated state in the decades previous to 1970 to a turbid, phytoplankton-dominated state by the mid 1970s. These changes were complexly linked with increasing eutrophication by black-headed gulls and increased salinity due to agricultural changes in the catchment.
• 2 At the turn of the 1970s, the lake began to change again and during the 1980s a submerged plant community, of tall, vigorously growing species (e.g. Myriophyllum spicatum, Patamogeton pectinatus) had recovered, despite a major reduction in the roosting gull population, no change in salinity, and only small reductions in phytoplankton biomass and total phosphorus concentration.
• 3 Recovery of the plants may be linked to grazing of periphyton on them by an increased population of a mysid Neomysis integer which had been suppressed by toxicity from an alga, Prymnesium parvum formerly stimulated by the ingress of gull guano.
• 4 A cladoceran community present in the clear-water phase has not recovered and may be suppressed by continued high salinities. Further restoration of the lake requires displacement of the large phytoplankton biomass and this might best be contemplated by land use changes leading to lowered salinity and predicted recovery of grazing Cladocera.
• 5 Models are given which summarize the likely workings of the system in the early twentieth century, the mid-twentieth century, the 1970s and the late 1980s.

     

The Karyotic Mineralization Window (KMW)

Biomineralization is frequently a transient and intermittentactivity characterised as a phase change in a small fluid-filledspace bounded by sensitive cells. It is therefore a difficultphenomenon to identify and to experiment upon. The possibilityhas therefore been pursued of obtaining a "Mineralization Window"onto this process by following the activities of mixtures oftrace amounts of inorganic ions. The results of a number ofsuch experiments are considered in relation to the three differenttypes of calcifying systems originally identified by Wilbur.The method of metal ion pairs is also of value in probing therelationships between amorphous deposits and the various crystallineminerals that may be formed from them.