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Specialist and generalist pathogens may exert different costs on their hosts; thereby altering the way hosts cope with environmental variation. We examined how pathogen-challenge alters the environmental conditions that maximize host... more
Specialist and generalist pathogens may exert different costs on their hosts; thereby altering the way hosts cope with environmental variation. We examined how pathogen-challenge alters the environmental conditions that maximize host performance by simultaneously varying temperature and nutrition (protein to carbohydrate ratio; P:C) after exposure to two baculoviruses; one that is specific to the cabbage looper, Trichoplusia ni (TnSNPV) and another that has a broad host range (AcMNPV). Virus-challenged larvae performed better on more protein-biased diets, primarily due to higher survival, whereas unchallenged larvae performed best on a balanced diet. The environmental conditions that maximized host performance differed with virus identity because TnSNPV-challenge inflicted fitness costs (reduced pupal weight and prolonged development) whereas AcMNPV-challenge did not. The performance of TnSNPV-challenged larvae rose with increasing P:C across all temperatures, whereas temperature mo...
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Many pathogens and parasites are present in host individuals and populations without any obvious signs of disease. This is particularly true for baculoviruses infecting lepidopteran hosts, where studies have shown that covert persistent... more
Many pathogens and parasites are present in host individuals and populations without any obvious signs of disease. This is particularly true for baculoviruses infecting lepidopteran hosts, where studies have shown that covert persistent viral infections are almost ubiquitous in many species. To date, the infection intensity of covert viruses has rarely been quantified. In this study, we investigated the dynamics of a covert baculovirus infection within the lepidopteran crop pest Spodoptera exempta. A real-time quantitative polymerase chain reaction (qPCR) procedure using a 5' nuclease hydrolysis (TaqMan) probe was developed for specific detection and quantification of Spodoptera exempta nucleopolyhedrovirus (SpexNPV). The qPCR assay indicated that covert baculovirus dynamics varied considerably over the course of the host life-cycle, with infection load peaking in early larval instars and being lowest in adults and final-instar larvae. Adult dissections indicated that, contrary to expectation, viral load aggregation was highest in the head, wings and legs, and lowest in the thorax and abdomen. The data presented here have broad implications relating to our understanding of transmission patterns of baculoviruses and the role of covert infections in host-pathogen dynamics.
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... et al. 1993). Closer examination of several host range studies show that up to 10% of the virus positive species were not necessarily killed by the virus they were challenged with (Doyle et al. 1990; Cory et al. 2000). Thus the ...
Beneficial alleles that spread rapidly as an adaptation to a new environment are often associated with costs that reduce the fitness of the population in the original environment. Several species of insect pests have evolved resistance to... more
Beneficial alleles that spread rapidly as an adaptation to a new environment are often associated with costs that reduce the fitness of the population in the original environment. Several species of insect pests have evolved resistance to Bacillus thuringiensis (Bt) toxins in the field, jeopardizing its future use. This has most commonly occurred through the alteration of insect midgut binding sites specific for Bt toxins. While fitness costs related to Bt resistance alleles have often been recorded, the mechanisms behind them have remained obscure. We asked whether evolved resistance to Bt alters dietary nutrient intake, and if reduced efficiency of converting ingested nutrients to body growth are associated with fitness costs and variation in susceptibility to Bt. We fed the cabbage looper Trichoplusia ni artificial diets differing in levels of dietary imbalance in two major macronutrients, protein and digestible carbohydrate. By comparing a Bt-resistant T. ni strain with a suscep...
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Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to... more
Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X10 polyhedra/ha, and the GV at 4 X10 granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sam...
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Research Interests: Population Dynamics, Multidisciplinary, Lepidoptera, Genetic Diversity, Population structure, and 14 moreFemale, Animals, Disease resistance, Male, British Columbia, PLoS one, Multiple Paternity, Multiple Mating, Genetic Differentiation, Family Structure, Genetic variation, High Density Concrete, Genetic Variability, and Population dynamic
Evolved resistance to xenobiotics and parasites is often associated with fitness costs when the selection pressure is absent. Resistance to the widely used microbial insecticide Bacillus thuringiensis (Bt) has evolved in several insect... more
Evolved resistance to xenobiotics and parasites is often associated with fitness costs when the selection pressure is absent. Resistance to the widely used microbial insecticide Bacillus thuringiensis (Bt) has evolved in several insect species through the modification of insect midgut binding sites for Bt toxins, and reports of costs associated with Bt resistance are common. Studies on the costs of Bt-resistance restrict the insect to a single artificial diet or host-plant. However, it is well documented that insects can self-select appropriate proportions of multiple nutritionally unbalanced foods to optimize life-history traits. Therefore, we examined whether Bt-resistant and susceptible cabbage loopers Trichoplusia ni differed in their nutrient intake and fitness costs when they were allowed to compose their own protein:carbohydrate diet. We found that Bt-resistant T. ni composed a higher ratio of protein to carbohydrate than susceptible T. ni. Bt-resistant males exhibited no fitness cost, while the fitness cost (reduced pupal weight) was present in resistant females. The absence of the fitness cost in resistant males was associated with increased carbohydrate consumption compared to females. We demonstrate a sex difference in a fitness cost and a new behavioural outcome associated with Bt resistance.
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Research Interests: Genetics, Geography, Demography, Population Dynamics, Genetic Diversity, and 17 moreMolecular Ecology, Biological Sciences, Population structure, Animals, Host Plant Resistance, Population Density, Spatial Scale, British Columbia, Local adaptation, Viral Infection, Moths, Genetic variation, Spatial structure, Vertical Transmission, Genetic Variability, Population dynamic, and Virus isolation
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The defence reaction of operculum closing in response to the presence of the molluscivorous leech Glossiphonia complanata (L.) and the non-molluscivorous Erpobdella octoculata (L.) was studied in four species of freshwater prosobranch... more
The defence reaction of operculum closing in response to the presence of the molluscivorous leech Glossiphonia complanata (L.) and the non-molluscivorous Erpobdella octoculata (L.) was studied in four species of freshwater prosobranch gastropod. Bithynia tentaculata (L.) and Valvata piscinalis (Mller) can distinguish between the leeches, reacting only to G. complanata. V. piscinalis is capable of a greater degree of distance chemoreception of the leech ‘scent’. Valvata cristata Mller and Potamopyrgus jenkinsi (Smith) did not react to either leech. V. cristata may not be a potential prey item for G. complanata, while P. jenkinsi is fed on by the leech, but is a relative newcomer to the freshwater fauna.
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Mixed-genotype infections are common in many natural host-parasite interactions. Classical kin-selection models predict that single-genotype infections can exploit host resources prudently to maximize fitness, but that selection favours... more
Mixed-genotype infections are common in many natural host-parasite interactions. Classical kin-selection models predict that single-genotype infections can exploit host resources prudently to maximize fitness, but that selection favours rapid exploitation when co-infecting genotypes share limited host resources. However, theory has outpaced evidence: we require empirical studies of pathogen genotypes that naturally co-infect hosts. Do genotypes actually compete within hosts? Can host ecology affect the outcome of co-infection? We posed both questions by comparing traits of infections in which two baculovirus genotypes were fed to hosts alongside inocula of the same or a different genotype. The host, Panolis flammea, is a herbivore of Pinus sylvestris and Pi. contorta. The pathogen, PfNPV (a nucleopolyhedrovirus), occurs naturally as mixtures of genotypes that differ, when isolated, in pathogenicity, speed of kill and yield. Single-genotype infection traits failed to predict the ...
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The genetic diversity of many DNA virus populations in nature is unknown, but for those that have been studied it has been found to be relatively high. This is particularly true for baculoviruses, a family of large double-stranded DNA... more
The genetic diversity of many DNA virus populations in nature is unknown, but for those that have been studied it has been found to be relatively high. This is particularly true for baculoviruses, a family of large double-stranded DNA viruses that infect the larval stages of insects. Why there should be such heterogeneity within these virus populations is puzzling and what sustains it is still unknown. It has long been recognized that some baculoviruses have a relatively wide host range, but the effect of different host species on the genotypic structure of a baculovirus population has received little attention. We provide evidence that infection of different insect species can influence the genetic diversity of a Panolis flammea nucleopolyhedrovirus (PaflNPV) population, isolated from the pine beauty moth. Variable regions of the PaflNPV genome were sequenced and novel ORFs were identified on each of the enlarged fragments. The roles of these orfs and the implications of their pres...