bluuebunny/crossref_metadata_2025_split huggingface dataset:
The functions of plant feeding in the omnivorous predator Dicyphus hesperus: water places limits on predation
Authors: Gillespie D. R. , Mcgregor R. R. 
Published: March 2003

Summary1. Dicyphus hesperus Knight (Heteroptera: Miridae) nymphs were fed from egg hatch to the adult stage on Ephestia kuehniella eggs provided either alone or in combination with tomato leaves or with a supplementary water source.2. Only 6% of individuals completed nymphal development on a diet of eggs alone. In contrast, a high proportion of nymphs completed development on a diet of eggs when either tomato leaves (97%) or a supplementary water source (88%) were provided.3. The development times of nymphs given access to leaves were significantly shorter than those of nymphs given access only to supplementary water.4. Adult female D. hesperus that were given access to tomato leaves prior to feeding trials consumed significantly more eggs in a 4‐h period than females that were dehydrated before trials. Dehydrated females that were allowed access to water for 3 h before trials consumed an intermediate number of eggs.5. Plant feeding or access to some other water source is required for prey feeding, growth, and development in D. hesperus, and acquisition of water is proposed as a primary function of plant feeding. In addition, D. hesperus derives nutrients from plant feeding that increase the rate of nymphal development, although nymphs cannot complete development when provided only with tomato leaves.6. Three simple models are presented of feeding behaviour in predatory Heteroptera where the amount of plant feeding either decreases, increases, or is constant as a function of the amount of prey feeding. The models are discussed with reference to the results and the probable multifunctional nature of plant feeding in predatory Heteroptera.
The occurrence and effectiveness of hypersensitive reaction against galling herbivores across host taxa
Authors: Fernandes G. Wilson , Negreiros Daniel 
Published: March 2003

Summary1. Hypersensitive reaction is an important type of induced defence by which the plant elicits a defence response to pathogens and insects. Hypersensitive reaction has been argued to be the most common plant resistance mechanism against insect herbivores that have intimate associations with their host plants.2. The work reported here attempted to establish how important and widespread hypersensitive reaction might be against gall‐forming species across host taxa.3. Hypersensitive reaction was the most important mortality factor against gall formation across host plant taxa in seven out of eight cases.4. The number of insect galls correlated with the size of the leaves but module (leaf) size was a weak factor influencing the incidence of plant hypersensitive reaction to galling.5. Insect galls and hypersensitive reactions occurred in genetically distant as well as geographically widespread host plant taxa.
Prey discrimination by a generalist coccinellid predator: effect of prey age or parasitism?
Authors: Roger Caroline , Coderre Daniel , Vigneault Clément , Boivin Guy 
Published: March 2003

Summary1. Patterns of prey discrimination by the generalist predatory coccinellid Coleomegilla maculata lengi Timb. (Coleoptera: Coccinellidae) were studied in relation to prey quality, under laboratory conditions.2. Choice experiments were performed in which second‐ and fourth‐instar coccinellids had the choice between Trichoplusia ni (Lepidoptera: Noctuidae) eggs that were young or old, unparasitised or parasitised by Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae).3. Coleomegilla maculata larvae did not exhibit any preference for parasitised or unparasitised eggs at a similar stage of development but always preferred younger eggs, regardless of whether or not they were parasitised. Furthermore, the percentage of rejection was higher and handling time longer on the less preferred egg type. Pre‐imaginal development time, food intake to reach adulthood, and survival of coccinellid immatures were altered when coccinellid larvae were fed with parasitised and old unparasitised eggs.4. These results indicate that C. maculata larvae select eggs based on their stage of development regardless of parasitism, and that prey quality of aged prey is lower.5. Fourth‐instar coccinellid larvae spent less time in patches containing solely parasitised old eggs, and their level of exploitation was greatly reduced, compared with homogeneous patches containing unparasitised young eggs. This suggests that C. maculata larvae respond to variable patch quality by using flexible decision rules that reflect the payoff of the patch.
The reproductive flight phenology of a neotropical ant assemblage
Authors: Kaspari Michael , Pickering John , Windsor Donald 
Published: March 2003

Summary1. Alate flights reflect an ant colony's investment in sexual reproduction and dispersal yet little is known about community‐wide patterns of alate phenology. Two Malaise traps (for 2 years) and two light traps (for 1 year) were used to explore the flight phenologies of 22 common neotropical species from Barro Colorado Island, Panama.2. The traps caught 23 182 individuals and 286 species/morphospecies. The two trap methods shared only 18 species. Samples also differed in sexual composition: light trap samples were 80% female, Malaise trap samples were 2.6% female.3. Of 22 common species, all but one flew over half the year, with about half flying every month of the year. These data, combined with a literature review, suggest a latitudinal gradient in alate flight season: one north temperate assemblage (42°N) averaged 1.6 lunar months per species. The ever‐warm tropical year provides a larger flight window that allows a diversity of phenologies, from continuous to strongly pulsed.4. Rainfall was correlated with alate flights in one‐third of the species. Quantile regression suggested that high weekly rainfall was necessary but not sufficient to produce alate flights in about a quarter of the species.5. By decreasing the number of nests releasing alates on a given day, long flight seasons may lower the probability of finding a mate. At the same time, long flight seasons may increase the opportunity of finding vacant nest sites. High population densities and high incidence of nest disturbance in this community may ameliorate the first cost while enhancing the second benefit.
The spatial distribution of beetles within the canopies of oak trees in Richmond Park, U.K.
Authors: Stork N. E. , Hammond P. M. , Russell B. L. , Hadwen W. L. 
Published: March 2003

Summary1. 5054 adult beetles of 144 species were collected in a total of 696 1‐m2 collecting trays by knockdown insecticide fogging of 36 different oak trees in closed canopy woodland at Richmond Park, U.K., with three of the trees sampled on each of 12 dates, at 2‐ to 3‐week intervals, between April and October 1984.2. In late spring (April/May), more individuals and species of beetles were collected in trays close to the trunks of trees than in trays more distant from the trunk. The reverse was the case in late September/October. Neither pattern prevailed in the intervening months.3. Individual species exhibited a variety of patterns, with some species more abundant near the trunk, e.g. Leiopus nebulosus (L.), Strophosoma melanogrammum (Forster), Cylindronotus laevioctostriatus (Goeze), and Dromius agilis (Fabricius), and some less abundant near the trunk, e.g. Curculio pyrrhoceras (Marsham) and Rhynchaenus signifer (Creutzer). For Adalia decempunctata (L.), this preference changed with season. The observed species preferences for parts of a tree crown near or distant from the main trunk are discussed with reference to their known biologies.4. No pronounced pattern of preference for north‐ or south‐facing aspects of trees in closed canopy woodland was observed, however populations of some species exhibited patterns of within‐tree distribution that correlate with compass angle; for one species, the ladybird Adalia decempunctata, this distribution changed with season and between colour morphs.
The nature of migration in the red admiral butterflyVanessa atalanta: evidence from the population ecology in its southern range
Authors: Stefanescu Constantí 
Published: March 2003

Summary1. The migrantVanessa atalanta(L.) occurs throughout Europe and North Africa. In autumn, populations emigrate from northern and central Europe to the Mediterranean region to overwinter. In the spring, the northern range is recolonised by migrants from the south. The dynamics of the species in the winter range is poorly known.2. From 1994 to 1999, adults and immatures ofV. atalantawere monitored all year round in Mediterranean habitats in north‐east Spain.3. Data showed that the Catalonia lowlands is an area to whichV. atalantamigrates to breed during the winter. Migrants arrive in October and early November and initiate a period of intensive breeding. Larval development occurs throughout the winter until a first annual generation of adults appears in early spring.4. Most of the butterflies emerging in the spring emigrate and leave the area without breeding. The data suggest strongly that recolonisation of the northern range is by these butterflies not by wintering adults. Altitudinal migration also seems to be a common phenomenon, allowing a further summer generation of adults to occur at high elevations within the Mediterranean region.5. The complex phenology ofV. atalantain its southern range has evolved as a strategy to track larval resources through space and time. Autumn migration coincides with the greatest availability of the main food plant,Urtica dioicaL. Late spring migration occurs by the time food quality is decreasing.
The phenological window of opportunity for early‐season birch sawflies
Authors: Martel Jocelyn , Kause Antti 
Published: March 2003

Abstract 1. The phenological window of opportunity hypothesis posits that an insect herbivore cannot survive outside a specific leaf age interval of its host plant.2. Previous studies have shown that mountain birch displays extensive seasonal changes in leaf biochemical characteristics. Young, expanding leaves are full of water and amino acids but they also contain large amounts of protein‐precipitating gallotannins as well as flavonoid‐glycosides. Concentrations of these compounds decline during leaf growth whereas concentrations of sugars and proanthocyanidins and leaf toughness increase.3. Adult birch sawflies hatch in early summer and oviposit on growing leaves, which compels larvae to feed on leaves that are already well developed. The purpose of this study was to test whether leaves that were younger and biochemically different from the leaves available under natural conditions are within the phenological window of opportunity for the larvae of two early‐season birch sawfly species, Amauronematus amplus Konow and Pristiphora alpestris (Konow).4. Amauronematus amplus larvae survived better and developed faster, and P. alpestris larvae developed faster and became bigger, on atypically young leaves compared with larvae reared on leaves encountered normally. Therefore, these species can exploit the putative nutritional superiority of very young leaves, which probably outweighs the potential impact of the new set of secondary metabolites offered to them. In conclusion, young leaves that are consumed rarely by sawfly larvae are within their phenological window of opportunity, even though the timing of sawfly life cycles constrains their utilisation.
Triangular fecundity function and ageing in ladybird beetles
Authors: Dixon A. F. G. , Agarwala B. K. 
Published: March 2003

Abstract1. In insects, the age schedules of fecundity tend to be triangular and this has been attributed more to temporal patterns of mortality than to fecundity. The objective of the work reported here was to test the assumption that senescence shapes the fecundity function in ladybird beetles, and in particular that the production function declines with age.2. The results of a laboratory study on three species of predatory ladybird beetle indicated that the efficiency with which these insects acquire and process food declined with age. Although supplied with the same amount of food each day, after the onset of reproduction, these beetles ate less and less with increasing age. Egg production mirrored the decline in aphid consumption. Associated with this was a decline in fertility, assimilation, and speed of locomotion with age.3. This study indicates that production declined with age and that this shaped the fecundity schedules in these ladybird beetles. In addition, the results indicated that ladybirds are income breeders and, as predicted, the reproductive effort of the small species was greater than that of the large species used in this study.
A minimalist approach to the effects of density‐dependent competition on insect life‐history traits
Authors: Agnew Philip , Hide Mallorie , Sidobre Christine , Michalakis Yannis 
Published: March 2003

Abstract  1. Due to its effects on the phenotypic and genotypic expression of life‐history traits, density‐dependent competition is an important factor regulating the growth of populations. Specifically for insects, density‐dependent competition among juveniles is often associated with increased juvenile mortality, delayed maturity, and reduced adult size.2. The aim of the work reported here was to test whether the established phenotypic effects of density‐dependent competition on life‐history traits could be reproduced in an experimental design requiring a minimal number of individuals. Larvae of the mosquito Aedes aegypti were reared at densities of one, two, or three individuals per standard Drosophila vial and in six different conditions of larval food availability. This design required relatively few individuals per independent replicate and included a control treatment where individuals reared at a density of one larva per vial experienced no density‐dependent interactions with other larvae.3. Increased larval densities or reduced food availability led to increased larval mortality, delayed pupation, and the emergence of smaller adults that starved to death in a shorter time (indicating emergence with fewer nutritional reserves).4. Female mosquitoes were relatively larger than males (as measured by wing length) but males tended to survive for longer. These differences increased as larval food availability increased, indicating the relative importance of these two traits for the fitness of each sex. The role of nutritional reserves for the reproductive success of males was highlighted in particular.5. This minimalist approach may provide a useful model for investigating the effects of density‐dependent competition on insect life‐history traits.
Metapopulation dynamics of a flightless alpine insectHemideina maoriin a naturally fragmented habitat
Authors: Leisnham Paul T. , Jamieson Ian G. 
Published: March 2003

Abstract1. Despite widespread acceptance of metapopulation theory, the effects that inter‐patch dispersal and variability in patch size have on metapopulation dynamics in insects are two issues that require further study. In addition, previous studies of metapopulations have tended to focus on organisms with high dispersal capabilities such as some species of butterfly and bird.2. Mountain stone wetaHemideina maoriare a long‐lived, flightless orthopteran that live onislandrock outcrops or tors in the alpine region of southern New Zealand. A total of 480 adults and 789 juveniles was marked over three seasons on four large and 14 small tors to assess the effects of habitat fragmentation on the population dynamics ofH. maori.3. Only 12 adults (2.5% of marked adults and 4.0% of recaptured adults) and two juveniles (0.3% of marked juveniles and 0.7% of recaptured juveniles) dispersed between tors. The mean dispersal distance was 361 m (range = 36–672 m). Larger tors supported larger populations and had a higher number of emigrants and immigrants while smaller tors had proportionally higher emigration and immigration rates. Although adults on large and small tors had similar mean lifespans, five extinction events and three recolonisation events occurred during the study period, all on small tors.4.Hemideina maoriconform to many of the predictions of metapopulation theory even though they are flightless, show relatively low dispersal rates, and occur at low densities. Extinction and colonisation events are more common on small tors but may be relatively unimportant for the long‐term survival of the metapopulation because they occur on the smallest habitat patches, which support the smallest proportion of the overall population.
Flexibility in the composition and concentration of amino acids in honeydew of the drepanosiphid aphidTuberculatus quercicola
Authors: Yao Izumi , Akimoto Shin‐Ichi 
Published: March 2003

Abstract1. Mutualistic interactions between aphids and ants are mediated by honeydew that aphids produce. Previous work showed that when attended by the antFormica yessensisForel (Hymenoptera: Formicidae), nymphs of the aphidTuberculatus quercicola(Matsumura) (Homoptera: Aphididae) developed into significantly smaller adults with lower fecundity than did nymphs that were not ant attended.2. This study tested the hypothesis that this cost of ant attendance arises through changes in the quality and quantity of honeydew. Ant‐attended and ant‐excluded aphid colonies were prepared in the field. The composition and concentration of amino acids were compared between the honeydew produced by ant‐attended colonies and that produced by ant‐excluded colonies.3. The aphids excreted smaller droplets of honeydew, but also excreted them more frequently, in ant‐attended colonies than in ant‐excluded colonies. The honeydew of ant‐attended aphids contained more types of amino acid, and a significantly higher total concentration of amino acids, than did the honeydew of ant‐excluded aphids.4. These results suggest that the increase in the concentration of amino acids in honeydew leads to a shortage of nitrogen available for aphid growth and reproduction, resulting in lower performance under ant attendance.5. With the advance of seasons, a significant reduction was found in both the total free amino acid concentration in phloem sap and the frequency of honeydew excretion; however the total concentration of amino acids in the honeydew did not vary significantly during the seasons, suggesting that aphids keep the quality of honeydew constant in order to maintain ant visitation.
Gemfibrozil‐induced decrease in serum ubiquinone and α‐ and γ‐tocopherol levels in men with combined hyperlipidaemia
Authors: Åberg  , Appelkvist  , Bröijersén  , Eriksson  , Angelin  , Hjemdahl  , Dallner  
Published: March 2003

BackgroundLow blood levels of antioxidants are associated with an increased risk of developing coronary artery disease. Lipophilic antioxidants are transported in lipoproteins, and hypolipidaemic therapy may therefore alter their blood concentrations.MethodsThe present randomized, placebo‐controlled cross‐over study of 21 men with combined hyperlipidaemia examines whether 10–12 weeks of gemfibrozil treatment affects the serum concentrations of the antioxidants ubiquinone‐10 or α‐ or γ‐tocopherol.ResultsGemfibrozil treatment lowered plasma triglycerides and both total and very low‐density lipoprotein (VLDL)‐cholesterol (P < 0.001 for all by
ANOVA), whereas high‐density lipoprotein (HDL)‐cholesterol increased (P < 0.001). The median serum levels of ubiquinone‐10 decreased from 1.30 μmol L−1 (interquartile range 0.87–1.71 μmol L−1) with placebo to 0.76 μmol L−1 (0.66–0.95) with gemfibrozil treatment (P < 0.001). Corresponding levels for α‐ and γ‐tocopherol were: 68.5 μmol L−1 (51.1–84.7) vs. 40.8 μmol L−1 (30.3–55.0) and 8.6 μmol L−1 (5.2–16.7) vs. 4.3 μmol L−1 (3.5–7.0) respectively (P < 0.001 for both). The decrease in serum antioxidants was also evident when standardized for total cholesterol (P < 0.05) or LDL‐cholesterol (P < 0.001). Normolipaemic control subjects had significantly lower antioxidant levels than placebo‐treated patients: ubiquinone 0.63 μmol L−1 (0.41–1.05), α‐tocopherol 34.3 μmol L−1 (27.3–45.6) and γ‐tocopherol 3.2 μmol L−1 (2.5–4.2) (P < 0.001 for all). The association of antioxidants with lipoprotein lipids was further established by positive correlations between the levels of antioxidants and those of total cholesterol (r = 0.64, P < 0.001) or total triglycerides (r = 0.71, P < 0.001).ConclusionGemfibrozil treatment of men with combined hyperlipidaemia reduces serum antioxidant levels to the levels seen in healthy normolipidaemic men. The mechanisms and the relevance of this finding remain unclear and need to be addressed in further studies.
Lack of influence of apolipoprotein E4 on lipoprotein levels in the island population of Sardinia
Authors: Deiana  , Pes  , Carru  , Errigo  , Pettinato  , Carcassi  , Baggio  , Contu  
Published: March 2003

BackgroundIn this study, the apolipoprotein E (apoE) genotypes as well as plasma lipid and lipoprotein levels have been determined for the first time in 633 healthy and unrelated inhabitants on the island of Sardinia (291 men and 342 women, age range 6–89 years), randomly selected in the four districts of Sardinia among healthy people having parents and grandparents born in the same geographic area. This island lies in the centre of the western Mediterranean sea with a well‐recognized peculiar and preserved genetic background. The ε3 allele frequency (0.897) is higher than that previously reported in southern and mainland Italy and is one of the highest in Europe and among Caucasians; ε2 allele frequency (0.040) is the lowest in Europe; ε4 (0.063) is unusually low and, most interestingly, does not change in the different age groups, i.e. does not decrease in old subjects.ResultsLipid and lipoprotein analysis confirm that total cholesterol and low‐density lipoprotein (LDL)‐cholesterol levels are lower than those described in mainland Italy; moreover, in this large Sardinian series, accurately selected, ε4 allele did not influence total cholesterol (P = 0.270), LDL‐cholesterol (P = 0.667) and high‐density lipoprotein (HDL)‐cholesterol (P = 0.549) as in other populations. In contrast, subjects carrying the ε2 allele were found to have significantly lower total cholesterol (P = 0.001) and LDL‐cholesterol (P = 0.001) levels than ε3 carriers.ConclusionThe low ε4 frequency and the lack of influence of this allele on lipid metabolism is a unique characteristic and, to date, has been described only in Sardinia among Caucasians; it might contribute to the low prevalence of coronary artery disease in this island.
A methylenetetrahydrofolate reductase gene polymorphism in ischaemic stroke and in carotid artery stenosis
Authors: Kostulas  , Crisby  , Huang  , Lannfelt  , Hagenfeldt  , Eggertsen  , Kostulas  , Hillert  
Published: March 2003

MethodsA biallelic polymorphism of the methylenetretrahydrofolate reductase (MTHFR) gene, reported to influence the plasma level of homocysteine (Hcy), was investigated for a possible role in influencing the risk of ischaemic cerebrovascular disease (ICVD) and occlusive atherosclerosis in 126 patients with ischaemic stroke and 70 patients with internal carotid artery (ICA) stenosis.ResultsOnly minor differences were observed between different groups of patients and control subjects. Although 47% of ICA stenosis patients had increased plasma Hcy, the MTHFR genotype did not correlate with levels of either Hcy, folic acid or vitamin B12. In addition, the MTHFR genotype did not affect Hcy levels, even in the presence of low blood folate.ConclusionWe conclude that this common MTHFR gene polymorphism does not exert a significant influence on the risk of developing ICVD or ICA stenosis, and does not cause the increased level of Hcy observed in ICA stenosis.