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Host Preference (host + preference)
Selected AbstractsPreference and performance of the hyperparasitoid Syrphophagus aphidivorus (Hymenoptera: Encyrtidae): fitness consequences of selecting hosts in live aphids or aphid mummiesECOLOGICAL ENTOMOLOGY, Issue 6 2004R. Buitenhuis Abstract., 1.,Theoretical models predict that ovipositional decisions of parasitoid females should lead to the selection of the most profitable host for parasitoid development. Most parasitoid species have evolved specific adaptations to exploit a single host stage. However, females of the aphid hyperparasitoid Syrphophagous aphidivorus (Mayr) (Hymenoptera: Encyrtidae) display a unique and atypical oviposition behaviour by attacking either primary parasitoid larvae in live aphids, or parasitoid pupae in dead, mummified aphids. 2.,In the laboratory, the correlation between host suitability and host preference of S. aphidivorus on the host Aphidius nigripes Ashmead parasitising the aphid Macrosiphum euphorbiae (Thomas) was investigated. 3.,The relative suitability of the two host stages was determined by measuring hyperparasitoid fitness parameters (survival, development time, fecundity, sex ratio, and adult size of progeny), and calculating the intrinsic rate of population increase (rm). Host preference by S. aphidivorus females and the influence of aphid defence behaviour on host selection was also examined. 4.,Hyperparasitoid offspring performance was highest when developing from hosts in aphid mummies and females consistently preferred this host to hosts in parasitised aphids. Although aphid defensive behaviour may influence host selection, it was not a determining factor. Ecological and evolutionary processes that might have led to dual oviposition behaviour in S. aphidivorus are discussed. [source] Host preference and performance of lichenivorous Eilema spp. larvae in relation to lichen secondary metabolitesJOURNAL OF ANIMAL ECOLOGY, Issue 3 2003Heikki Pöykkö Summary 1We compared the larval host preference of four lichenivorous Eilema (Lepidoptera, Arctiidae) species on four common epiphytic lichen species including Hypogymnia physodes, Melanelia exasperata, Vulpicida pinastri and Xanthoria parietina. Survival and growth of larvae on different species were monitored and correlation to qualitative and quantitative variation in lichen secondary compounds was analysed. 2All moth species preferred M. exasperata, which does not contain polyphenolic substances, over other lichens, but also foraged on other lichens in the food preference experiment. All larvae reared on V. pinastri and H. physodes died during the growth and survival experiment. Survival of larvae on X. parietina and M. exasperata were equal. Larvae grew faster and and bigger on M. exasperata than on other lichens. 3Consumption and utilization measurements also revealed that M. exasperata was of the highest quality, although the relative consumption rate was highest on X. parietina. Our results indicate that different secondary chemicals have different effect against lichenivores or that larvae are either well adapted to certain chemicals or that these chemicals may have other roles than antiherbivore function for lichens. 4It is suggested that lichenivorous lepidopteran species may have different adaptations, such as dietary mixing to receive nutrients in optimal proportions or compensatory feeding ability to ensure the maximal growth efficiency on a suboptimal host. [source] Identification and expression of odorant-binding proteins of the malaria-carrying mosquitoes Anopheles gambiae and Anopheles arabiensisARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2005Zheng-Xi Li Abstract Host preference and blood feeding are restricted to female mosquitoes. Olfaction plays a major role in host-seeking behaviour, which is likely to be associated with a subset of mosquito olfactory genes. Proteins involved in olfaction include the odorant receptors (ORs) and the odorant-binding proteins (OBPs). OBPs are thought to function as a carrier within insect antennae for transporting odours to the olfactory receptors. Here we report the annotation of 32 genes encoding putative OBPs in the malaria mosquito Anopheles gambiae and their tissue-specific expression in two mosquito species of the Anopheles complex; a highly anthropophilic species An. gambiae sensu stricto and an opportunistic, but more zoophilic species, An. arabiensis. RT-PCR shows that some of the genes are expressed mainly in head tissue and a subset of these show highest expression in female heads. One of the genes (agCP1588) which has not been identified as an OBP, has a high similarity (40%) to the Drosophila pheromone-binding protein 4 (PBPRP4) and is only expressed in heads of both An. gambiae and An. arabiensis, and at higher levels in female heads. Two genes (agCP3071 and agCP15554) are expressed only in female heads and agC15554 also shows higher expression levels in An. gambiae. The expression profiles of the genes in the two members of the Anopheles complex provides the first step towards further molecular analysis of the mosquito olfactory apparatus. Arch. Insect Biochem. Physiol. 58:175,189, 2005. © 2005 Wiley-Liss, Inc. [source] Inconsistent use of host plants by the Alaskan swallowtail butterfly: adult preference experiments suggest labile oviposition strategyECOLOGICAL ENTOMOLOGY, Issue 2 2007SHANNON M. MURPHY Abstract 1.,The Alaskan swallowtail butterfly (Papilio machaon aliaska) uses three unrelated plant species as hosts: Cnidium cnidiifolium (Apiaceae), Artemisia arctica (Asteraceae), and Petasites frigidus (Asteraceae). The research presented here investigated whether there are any consistent patterns in host choice by P. m. aliaska females. 2.,The first two experiments were designed to test if P. m. aliaska host preference is constant or if it changes from day to day. If host preference is labile, the experiments were designed to also test whether a female's diet breadth narrows or expands over time. 3.,The third experiment tested the host preferences of female offspring from several wild-caught P. m. aliaska females. If P. m. aliaska individuals are specialised in their host use, then all of the offspring from a single female would likely prefer the same host-plant species. This experiment was also designed to test the Hopkins' host selection principle; does the food plant on which a female is reared as a larva influence her future choices when she is searching for host plants for her own offspring? 4.,The results from all of these experiments indicate that P. m. aliaska females vary greatly in their oviposition behaviour and in their preferences for the three host plants. Most populations appear to consist of generalists with labile oviposition behaviour. There is no evidence to support the Hopkins' host selection principle. 5.,It is suggested that the generalised selection of host plants by P. m. aliaska females may be a ,bet-hedging' strategy and that this strategy may maximise reproductive fitness in an unpredictable environment. [source] Preference and performance of the hyperparasitoid Syrphophagus aphidivorus (Hymenoptera: Encyrtidae): fitness consequences of selecting hosts in live aphids or aphid mummiesECOLOGICAL ENTOMOLOGY, Issue 6 2004R. Buitenhuis Abstract., 1.,Theoretical models predict that ovipositional decisions of parasitoid females should lead to the selection of the most profitable host for parasitoid development. Most parasitoid species have evolved specific adaptations to exploit a single host stage. However, females of the aphid hyperparasitoid Syrphophagous aphidivorus (Mayr) (Hymenoptera: Encyrtidae) display a unique and atypical oviposition behaviour by attacking either primary parasitoid larvae in live aphids, or parasitoid pupae in dead, mummified aphids. 2.,In the laboratory, the correlation between host suitability and host preference of S. aphidivorus on the host Aphidius nigripes Ashmead parasitising the aphid Macrosiphum euphorbiae (Thomas) was investigated. 3.,The relative suitability of the two host stages was determined by measuring hyperparasitoid fitness parameters (survival, development time, fecundity, sex ratio, and adult size of progeny), and calculating the intrinsic rate of population increase (rm). Host preference by S. aphidivorus females and the influence of aphid defence behaviour on host selection was also examined. 4.,Hyperparasitoid offspring performance was highest when developing from hosts in aphid mummies and females consistently preferred this host to hosts in parasitised aphids. Although aphid defensive behaviour may influence host selection, it was not a determining factor. Ecological and evolutionary processes that might have led to dual oviposition behaviour in S. aphidivorus are discussed. [source] When random sampling does not work: standard design falsely indicates maladaptive host preferences in a butterflyECOLOGY LETTERS, Issue 1 2002Michael C. Singer In experiments that investigate species' interactions, individuals are often chosen at random to represent their populations. However, this practice can generate misleading results when individuals of different species do not interact at random. We illustrate this effect by examining oviposition preferences of Euphydryas aurinia butterflies from three populations using three different plant genera. We first offered each insect a randomly chosen member of its own host population and a foreign host (Succisa pratensis) not present in the insect's habitat. The butterflies uniformly preferred the foreign Succisa over their own hosts. Preferences were apparently maladaptive because insects wasted time searching for a nonexistent plant. We repeated the experiment using individual hosts that had naturally received eggs in the field. The overall preference for Succisa and the appearance of maladaptation both disappeared. In the original experiments, our random choice of experimental host individuals had combined with strong within-species discrimination by the butterflies and with overlap of acceptability between host species to obscure the true nature of host preference. [source] Resistance of apple trees to Cydia pomonella egg-laying due to leaf surface metabolitesENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Nadia Lombarkia Abstract During host plant selection and particularly after alighting on a plant, chemical cues from the plant surface influence an insect's acceptance of the plant and, subsequently, its egg-laying behaviour. Primary metabolites in the phylloplane may be more important than hitherto known. We have shown that soluble carbohydrates, such as glucose, fructose, and sucrose, and sugar alcohols, such as sorbitol, quebrachitol, and myo -inositol, can be detected by insects after contacting the plant and that they positively influence egg-laying of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), on apple trees. We addressed the question whether a lack of these substances could also explain apple tree resistance to C. pomonella in terms of reduced egg-laying. Leaf surface washings were collected in an apple orchard by spraying water on the resistant cultivar X65-11 and on the susceptible cultivar P5R50A4. The washings were tested on a nylon cloth on isolated females under no-choice conditions. The washings were analysed and synthetic blends, each consisting of the six metabolites in the proportions established in the leaf surface washings of both cultivars, were then tested for their effect on egg-laying of C. pomonella. Dose,response egg-laying tests were carried out on substrates impregnated with the X65-11 leaf surface blend at 1, 100, 1 000, and 10 000 times the natural dose. Egg-laying behaviour in the bioassays with leaf surface washings of both cultivars closely resembled egg-laying in the orchard. Washings of P5R50A4 stimulated egg-laying to a greater extent than those of X65-11 and the water control. Synthetic blends reduced substrate acceptance and egg-laying, compared to the washings of X65-11. Ratios between components within the blend are responsible for this resistance. In conclusion, quantities and ratios of the six primary metabolites found on the leaf surface may influence host preference of C. pomonella as well as their egg-laying behaviour, thus they may play a role in the trees' resistance to the codling moth. [source] A tritrophic analysis of host preference and performance in a polyphagous leafminerENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2006Martín Videla Abstract The optimal oviposition theory predicts that oviposition preferences of phytophagous insects should correlate with host suitability for their offspring. As plant host suitability depends not only on its quality as food, but also on its provision of enemy-free space, we examined the relationship between adult host preference and offspring performance for the leafminer Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae) on various host plants, considering also the interaction with natural enemies. Preference and offspring performance were assessed through observational field data and laboratory experiments in central Argentina. Field data suggested a positive host preference , performance linkage, as the leafminer attained larger body size on the crops where it was more abundant. Laboratory trials supported these results: Vicia faba L. (Fabaceae) was the preferred host in the laboratory as well as in the field, performance of L. huidobrensis being also best on this host, with highest survival rates and shortest development time. The actively feeding larval stage showed the largest plant-related effects. Higher overall parasitism rates were found on plants from which smaller leafminers were reared, reinforcing the preference,performance linkage. On the other hand, the main parasitoid Phaedrotoma scabriventris Nixon (Hymenoptera: Braconidae) reached larger body size, and caused higher mortality rates on crops where the leafminer was larger. Changes in abundance of particular parasitoid species could thus modify overall parasitism trends. [source] Does mother really know best?ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2005Oviposition preference reduces reproductive performance in the generalist parasitoid Aphidius ervi Abstract The reproductive success of female parasitoids is dependent on their ability to accurately assess the suitability of a host for larval development. For generalist parasitoids, which utilize a broad range of species and instars as hosts, a set of assessment criteria determines whether a host is accepted or rejected. The suitability of a host, however, can only be imperfectly assessed by the female parasitoid, which can result in the selection of lesser quality hosts for oviposition. In this study we explored the disparity between host quality and host preference using the generalist koinobiotic parasitoid Aphidius ervi Haliday (Hymenoptera: Aphidiidae) and the host Aulacorthum solani (Harris) (Homoptera: Aphididae), the foxglove aphid. The second instar hosts produced the highest level of reproductive success, while third and fourth instars resulted in a substantially reduced reproductive performance. When given a choice of host instars, parasitoids preferred the older hosts for oviposition disregarding their reduced suitability for larval development. Results are discussed in context of mechanisms involved in A. ervi host selection and biases in the criteria used to assess hosts that may arise when parasitoids transfer host species between generations. [source] Techniques for continuous rearing and assessing host preference of a multivoltine leaf-mining moth, Acrocercops transecta (Lepidoptera: Gracillariidae)ENTOMOLOGICAL SCIENCE, Issue 3 2005Issei OHSHIMA Abstract Techniques for rearing the leaf-mining moth Acrocercops transecta successively over several generations are described. Based on continuous rearing, some life historical parameters in A. transecta were determined. Because of its short generation time, successive rearing makes the moth suitable for mating experiments and a model organism to elucidate the mechanism of host-associated speciation. [source] SEQUENTIAL RAPID ADAPTATION OF INDIGENOUS PARASITOID WASPS TO THE INVASIVE BUTTERFLY PIERIS BRASSICAEEVOLUTION, Issue 8 2007Shingo Tanaka The introduction of a new species can change the characteristics of other species within a community. These changes may affect discontiguous trophic levels via adjacent trophic levels. The invasion of an exotic host species may provide the opportunity to observe the dynamics of changing interspecific interactions among parasitoids belonging to different trophic levels. The exotic large white butterfly Pieris brassicae invaded Hokkaido Island, Japan, and quickly spread throughout the island. Prior to the invasion, the small white butterfly P. rapae was the host of the primary parasitoid Cotesia glomerata, on which both the larval hyperparasitoid Baryscapus galactopus and the pupal hyperparasitoid Trichomalopsis apanteroctena depended. At the time of the invasion, C. glomerata generally laid eggs exclusively in P. rapae. During the five years following the invasion, however, the clutch size of C. glomerata in P. rapae gradually decreased, whereas the clutch size in P. brassicae increased. The field results corresponded well with laboratory experiments showing an increase in the rate of parasitism in P. brassicae. The host expansion of C. glomerata provided the two hyperparasitoids with an opportunity to choose between alternative hosts, that is, C. glomerata within P. brassicae and C. glomerata within P. rapae. Indeed, the pupal hyperparasitoid T. apanteroctena shifted its preference gradually to C. glomerata in P. brassicae, whereas the larval hyperparasitoid B. galactopus maintained a preference for C. glomerata in P. rapae. These changes in host preference may result from differential suitability of the two host types. The larval hyperparasitoid preferred C. glomerata within P. rapae to C. glomerata within P. brassicae, presumably because P. brassicae larvae attacked aggressively, thereby hindering the parasitization, whereas the pupal hyperparasitoid could take advantage of the competition-free resource by shifting its host preference. Consequently, the invasion of P. brassicae has changed the host use of the primary parasitoid C. glomerata and the pupal hyperparasitoid T. apanteroctena within a very short time. [source] A NOVEL PREFERENCE FOR AN INVASIVE PLANT AS A MECHANISM FOR ANIMAL HYBRID SPECIATIONEVOLUTION, Issue 2 2007Dietmar Schwarz Homoploid hybrid speciation,speciation via hybridization without a change in chromosome number,is rarely documented and poorly understood in animals. In particular, the mechanisms by which animal homoploid hybrid species become ecologically and reproductively isolated from their parents are hypothetical and remain largely untested by experiments. For the many host-specific parasites that mate on their host, choosing the right host is the most important ecological and reproductive barrier between these species. One example of a host-specific parasite is the Lonicera fly, a population of tephritid fruit flies that evolved within the last 250 years likely by hybridization between two native Rhagoletis species following a host shift to invasive honeysuckle. We studied the host preference of the Lonicera fly and its putative parent species in laboratory experiments. The Lonicera fly prefers its new host, introduced honeysuckle, over the hosts of both parental species, demonstrating the rapid acquisition of preference for a new host as a means of behavioral isolation from the parent species. The parent taxa discriminate against each other's native hosts, but both accept honeysuckle fruit, leaving the potential for asymmetric gene flow from the parent species. Importantly, this pattern allows us to formulate hypotheses about the initial formation of the Lonicera fly. As mating partners from the two parent taxa are more likely to meet on invasive honeysuckle than on their respective native hosts, independent acceptance of honeysuckle by both parents likely preceded hybridization. We propose that invasive honeysuckle served as a catalyst for the local breakdown of reproductive isolation between the native parent species, a novel consequence of the introduction of an exotic weed. We describe behavioral mechanisms that explain the initial hybridization and subsequent reproductive isolation of the hybrid Lonicera fly. These results provide experimental support for a combination of host shift and hybridization as a model for hybrid speciation in parasitic animals. [source] Oxidative metabolic profiles of Brucella strains isolated from marine mammals: contribution to their species classificationFEMS MICROBIOLOGY LETTERS, Issue 2 2007Isabelle Jacques Abstract Since the 1990s, Brucella strains not matching the characteristics of any of the six conventional species have been isolated worldwide from marine mammals. In this study, 31 Brucella strains isolated from various marine mammals were examined for their oxidative metabolic pattern on 12 amino-acid and carbohydrate substrates. Three main oxidative profiles different from those of the Brucella terrestrial mammal strains were identified for the marine mammal strains: one gathering strains isolated from pinnipeds and two gathering strains from cetaceans. Thus, both oxidative metabolism results and previous molecular studies are in agreement with the proposal of two new Brucella species, Brucella pinnipediae and Brucella cetaceae, to classify the Brucella strains isolated from marine mammals, and are also in accordance with a classification of species of the Brucella genus based on host preference. [source] High-nickel insects and nickel hyperaccumulator plants: A reviewINSECT SCIENCE, Issue 1 2009Robert S. Boyd Abstract Insects can vary greatly in whole-body elemental concentrations. Recent investigations of insects associated with Ni hyperaccumulator plants have identified insects with relatively elevated whole-body Ni levels. Evaluation of the limited data available indicates that a whole-body Ni concentration of 500 ,g Ni/g is exceptional: I propose that an insect species with a mean value of 500 ,g Ni/g or greater, in either larval/nymphal or adult stages, be considered a "high-Ni insect". Using the 500 ,g Ni/g criterion, 15 species of high-Ni insects have been identified to date from studies in Mpumalanga (South Africa), New Caledonia and California (USA). The highest mean Ni concentration reported is 3 500 ,g Ni/g for nymphs of a South African Stenoscepa species (Orthoptera: Pyrgomorphidae). The majority of high-Ni insects (66%) are heteropteran herbivores. Studies of high-Ni insect host preference indicate they are monophagous (or nearly so) on a particular Ni hyperaccumulator plant species. Much of the Ni in bodies of these insects is in their guts (up to 66%,75%), but elevated levels have also been found in Malpighian tubules, suggesting efficient elimination as one strategy for dealing with a high-Ni diet. Tissue levels of Ni are generally much lower than gut concentrations, but up to 1200 ,g Ni/g has been reported from exuviae, suggesting that molting may be another pathway of Ni elimination. One ecological function of the high Ni concentration of these insects may be to defend them against natural enemies, but to date only one experimental test has supported this "elemental defense" hypothesis. Community-level studies indicate that high-Ni insects mobilize Ni into food webs but that bioaccumulation of Ni does not occur at either plant-herbivore or herbivore-predator steps. Unsurprisingly, Ni bioaccumulation indices are greater for high-Ni insects compared to other insect species that feed on Ni hyperaccumulator plants. There is some evidence of Ni mobilization into food webs by insect visitors to flowers of Ni hyperaccumulator plants, but no high-Ni insect floral visitors have been reported. [source] Host preference and performance of lichenivorous Eilema spp. larvae in relation to lichen secondary metabolitesJOURNAL OF ANIMAL ECOLOGY, Issue 3 2003Heikki Pöykkö Summary 1We compared the larval host preference of four lichenivorous Eilema (Lepidoptera, Arctiidae) species on four common epiphytic lichen species including Hypogymnia physodes, Melanelia exasperata, Vulpicida pinastri and Xanthoria parietina. Survival and growth of larvae on different species were monitored and correlation to qualitative and quantitative variation in lichen secondary compounds was analysed. 2All moth species preferred M. exasperata, which does not contain polyphenolic substances, over other lichens, but also foraged on other lichens in the food preference experiment. All larvae reared on V. pinastri and H. physodes died during the growth and survival experiment. Survival of larvae on X. parietina and M. exasperata were equal. Larvae grew faster and and bigger on M. exasperata than on other lichens. 3Consumption and utilization measurements also revealed that M. exasperata was of the highest quality, although the relative consumption rate was highest on X. parietina. Our results indicate that different secondary chemicals have different effect against lichenivores or that larvae are either well adapted to certain chemicals or that these chemicals may have other roles than antiherbivore function for lichens. 4It is suggested that lichenivorous lepidopteran species may have different adaptations, such as dietary mixing to receive nutrients in optimal proportions or compensatory feeding ability to ensure the maximal growth efficiency on a suboptimal host. [source] Differential defoliation of Eucalyptus grandis arises from indiscriminant oviposition and differential larval survivalAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2009M. L. Henery Abstract 1,The influence of six open-pollinated families (OPFs) of Eucalyptus grandis on both the growth and development of larvae and the oviposition preference of a paropsine chrysomelid (Paropsis atomaria) was investigated. The OPFs had previously been identified as differing in their susceptibility to defoliation by P. atomaria in forestry progeny trials. 2,Oviposition preference for resistant and susceptible foliage was tested using binary choice tests. These tests did not demonstrate any significant preference for either resistant or susceptible open-pollinated material indicating that adult host preference for susceptible trees was not a likely cause of differential defoliation. 3,Quantification and analysis of growth and development parameters for all larval stages of P. atomaria showed that feeding on genetic material identified as resistant resulted in a significant reduction of relative growth rate of first instar larvae and an alteration to normal feeding behaviour. There was also a trend towards increased larval mortality on resistant E. grandis. 4,We argue that although the magnitude of these effects was minor, interactions with additional biotic and abiotic sources of mortality in the field have the potential, when magnified over successive generations, to result in significant variation in defoliation of host genotypes in the field. [source] Host Specialization among Vegetative Compatibility Groups of Verticillium dahliae in Relation to Verticillium longisporumJOURNAL OF PHYTOPATHOLOGY, Issue 3 2002K. ZEISE A collection of 24 isolates of Verticillium dahliae and 10 isolates of Verticillium longisporum originating from nine different host plants and from several geographic regions was tested for host specificity on 11 economically important crops such as potato, tomato, strawberry, linseed, three legumes and four Brassica species. In order to reveal host specificity the potential of each isolate to induce disease and affect plant yield was recorded for all isolate,host combinations. The collected data were statistically processed by means of a cluster analysis. As a result, the host range of individual isolates was found to be more dependent on the vegetative compatibility group (VCG) of the isolate than on its original host plant provenance. Twenty-two out of 24 V. dahliae isolates belonged to either VCG 2B or 4B. VCG 2B isolates showed specificity for legumes, strawberry, potato and linseed, whereas VCG 4B was specifically virulent on potato, strawberry and linseed. Subgroups within VCG 2B and 4B almost lacking any host preference were designated 2B* and 4B*. Three isolates from VCG 2B*, however, severely attacked tomato which is a host outside the authentic host range of VCG 2B. The pathogenicity of V. longisporum isolates was restricted to cruciferous hosts. Conversely, cruciferous plants were not affected by isolates from VCGs 2B and 4B of V. dahliae. This lack of cross-infectivity of certain subpopulations of V. dahliae and of V. longisporum may be useful in the management of this soil-borne wilt disease. [source] Vector competence of Culicoides species and the seroprevalence of homologous neutralizing antibody in horses for six serotypes of equine encephalosis virus (EEV) in South AfricaMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2004J. T. Paweska Abstract., Field-collected Culicoides species (Diptera: Ceratopogonidae) were fed on horse blood,virus mixtures containing one of the six serotypes of equine encephalosis virus (EEV1 to EEV6). The virus mean titres in the bloodmeals varied between 6.1 and 7.0 log10TCID50/mL. Of 19 Culicoides species assayed after 10 days extrinsic incubation at 23.5°C, five yielded the challenge virus, namely Culicoides (Avaritia) imicola Kieffer (EEV1,6), C. (A.) bolitinos Meiswinkel (EEV1, 2, 4, 6), C. (Meijerehelea) leucostictus Kiefer (EEV1, 2), C. (Culicoides) magnus Colaço (EEV1) and C. (Hoffmania) zuluensis de Meillon (EEV2). Virus recovery rates ranged from 0.5 to 13%. The mean levels of viral replication differed between serotypes and Culicoides species and ranged from 1.0 to 2.3 log10TCID50/midge. Culicoides midges shown in this study to be susceptible to oral infection with EEV are widely distributed in South Africa but differ considerably in their abundance, host preference and breeding sites. Of 1456 horses tested, 1144 (77%) had antibody to EEV. Homologous virus-neutralizing antibodies to all six serotypes were detected in individual horses from all eight geographical provinces of South Africa. The distribution, prevalence, and the rate of exposure to individual serotypes varied significantly between regions. The potential for vectoring of EEV in the field by several Culicoides species with unique ecologies and lack of cross-protection to re-infection with multiple serotypes highlights some of the mechanisms that are likely to play a role in the virus' natural maintenance cycle and the highly efficient level of countrywide transmission amongst South African horses. [source] Cultivar preference exhibited by two sympatric and genetically distinct populations of the soybean fungal pathogen Phialophora gregata f.sp. sojaePLANT PATHOLOGY, Issue 2 2005X. Meng Phialophora gregata f.sp. sojae, a soilborne vascular pathogen causing brown stem rot of soybean, has been divided into A and B populations based on variation in the intergenic spacer region of nuclear rDNA (rDNA marker). The A and B populations correlate with defoliating and nondefoliating pathotypes, respectively. In this study, eight additional polymorphic anonymous marker loci (five inter simple sequence repeat loci and three long-primer random amplified polymorphic DNA loci) were identified and applied to a total of 189 isolates. Alleles of these eight loci were invariant within, but different between the A and B populations, providing further evidence that the rDNA marker identifies genetically distinct populations. The two populations were sympatric, residing not only in the same field, but also in the same plants under field conditions. Representative strains of the two populations, when used individually in inoculations, infected both resistant cv. Bell and susceptible cv. Sturdy. However, when the same representatives of the two populations were mixed in a 1 : 1 ratio and used as a mixed inoculum in a competitive bioassay, differential cultivar preference was revealed using PCR detection of populations in infected plants. Population A was detected significantly more often (18 out of 24 plants) in the susceptible cv. Sturdy, whereas population B was detected significantly more often (17 out of 24 plants) in the resistant cv. Bell, corroborating earlier field studies. This is the first controlled experiment to demonstrate a differential host preference of P. gregata f.sp. sojae toward different cultivars of the same host species. Unification of terminologies used in P. gregata f.sp. sojae is discussed. [source] Genetic diversity, presence of the syrB gene, host preference and virulence of Pseudomonas syringae pv. syringae strains from woody and herbaceous host plantsPLANT PATHOLOGY, Issue 3 2003M. Scortichini A total of 101 Pseudomonas syringae pv. syringae strains, obtained from international culture collections or isolated from diseased tissues of herbaceous and woody plant species, were assessed by repetitive PCR using the BOX primer, and for the presence of the syrB gene. Representative strains were also tested for pathogenicity to lilac, pear, peach, corn and bean, as well as for virulence to lemon and zucchini fruits. The unweighted pair-group method using arithmethic averages analysis (UPGMA) of genomic fingerprints revealed 17 different patterns which grouped into three major clusters, A, B and C. Most of the strains (52·4%) were included in patterns 1,4 of group A. These patterns comprised strains obtained from either herbaceous or woody species, and showed four fragments of similar mobility. Genetic variability was ascertained for strains isolated from apple, pear, apricot, Citrus spp. and cereals. No clear relationship was observed between host plant and bacterial genomic fingerprint. Variability was also observed in pathogenicity and virulence tests. The inoculation of pear leaves discriminated strains isolated from pear as well as the very aggressive strains, whereas inoculation of lilac, peach and corn did not discriminate the host plant from which the strains were originally isolated. Lemon fruit inoculation proved very effective for P. syringae pv. syringae virulence assessment. The syrB gene was present in almost all strains. [source] Evidence for differential host preference in Microdochium nivale var. majus and Microdochiumnivale var. nivalePLANT PATHOLOGY, Issue 2 2000D.R. Simpson The pathogenicity of Microdochium nivale var. majus and var. nivale was tested on wheat, rye and oat seedlings using both visual disease scoring and quantitative PCR measurements. In an individual inoculation trial at 10°C var. majus and var. nivale were strongly pathogenic towards wheat and rye, with var. nivale causing slightly greater disease in rye. At this temperature only var. nivale caused significant disease of oats. In a further experiment M. nivale was inoculated as a series of mixtures of the two varieties and incubated at 15°C. The ratio of the varieties present in the inoculum and present at harvest was analysed by quantitative PCR and this enabled a coefficient of selection to be calculated for the varieties on each host. M. nivale var. majus showed a weak selective advantage over var. nivale on wheat (0.33 ± 0.08) and oat seedlings (0.35 ± 0.016) and M. nivale var. nivale showed a strong selective advantage over var. majus on rye seedlings (0.92 ± 0.26). The isolates were also compared for sensitivity to benzoxazolinone (BOA), a hydroxamic acid compound derived from rye leaves. M. nivale var majus was found to be significantly more sensitive to BOA than M. nivale var. nivale, indicating a possible mechanism for the selective advantage of var. nivale growing on rye. This is the first substantiated indication of a significant difference in host preference between Microdochium nivale var. majus and var. nivale. [source] Pirate ants (Polyergus breviceps) and sympatric hosts (Formica occulta and Formica sp. cf. argentea): host specificity and coevolutionary dynamicsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2007JEREMY M. BONO The pace and trajectory of coevolutionary arms races between parasites and their hosts are strongly influenced by the number of interacting species. In environments where a parasite has access to more than one host species, the parasite population may become divided in preference for a particular host. In the present study, we show that individual colonies of the pirate ant Polyergus breviceps differ in host preference during raiding, with each colony specializing on only one of two available Formica host species. Moreover, through genetic analyses, we show that the two hosts differ in their colony genetic structure. Formica occulta colonies were monogynous, whereas Formica sp. cf. argentea colonies were polygynous and polydomous (colonies occupy multiple nest sites). This difference has important implications for coevolutionary dynamics in this system because raids against individual nests of polydomous colonies have less impact on overall host colony fitness than do attacks on intact colonies. We also used primers that we designed for four microsatellite loci isolated from P. breviceps to verify that colonies of this species, like other pirate ants, are comprised of simple families headed by one singly mated queen. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 565,572. [source] Inconsistent use of host plants by the Alaskan swallowtail butterfly: adult preference experiments suggest labile oviposition strategyECOLOGICAL ENTOMOLOGY, Issue 2 2007SHANNON M. MURPHY Abstract 1.,The Alaskan swallowtail butterfly (Papilio machaon aliaska) uses three unrelated plant species as hosts: Cnidium cnidiifolium (Apiaceae), Artemisia arctica (Asteraceae), and Petasites frigidus (Asteraceae). The research presented here investigated whether there are any consistent patterns in host choice by P. m. aliaska females. 2.,The first two experiments were designed to test if P. m. aliaska host preference is constant or if it changes from day to day. If host preference is labile, the experiments were designed to also test whether a female's diet breadth narrows or expands over time. 3.,The third experiment tested the host preferences of female offspring from several wild-caught P. m. aliaska females. If P. m. aliaska individuals are specialised in their host use, then all of the offspring from a single female would likely prefer the same host-plant species. This experiment was also designed to test the Hopkins' host selection principle; does the food plant on which a female is reared as a larva influence her future choices when she is searching for host plants for her own offspring? 4.,The results from all of these experiments indicate that P. m. aliaska females vary greatly in their oviposition behaviour and in their preferences for the three host plants. Most populations appear to consist of generalists with labile oviposition behaviour. There is no evidence to support the Hopkins' host selection principle. 5.,It is suggested that the generalised selection of host plants by P. m. aliaska females may be a ,bet-hedging' strategy and that this strategy may maximise reproductive fitness in an unpredictable environment. [source] When random sampling does not work: standard design falsely indicates maladaptive host preferences in a butterflyECOLOGY LETTERS, Issue 1 2002Michael C. Singer In experiments that investigate species' interactions, individuals are often chosen at random to represent their populations. However, this practice can generate misleading results when individuals of different species do not interact at random. We illustrate this effect by examining oviposition preferences of Euphydryas aurinia butterflies from three populations using three different plant genera. We first offered each insect a randomly chosen member of its own host population and a foreign host (Succisa pratensis) not present in the insect's habitat. The butterflies uniformly preferred the foreign Succisa over their own hosts. Preferences were apparently maladaptive because insects wasted time searching for a nonexistent plant. We repeated the experiment using individual hosts that had naturally received eggs in the field. The overall preference for Succisa and the appearance of maladaptation both disappeared. In the original experiments, our random choice of experimental host individuals had combined with strong within-species discrimination by the butterflies and with overlap of acceptability between host species to obscure the true nature of host preference. [source] Beta diversity of plant,insect food webs in tropical forests: a conceptual frameworkINSECT CONSERVATION AND DIVERSITY, Issue 1 2009VOJTECH NOVOTNY Abstract., 1Beta diversity of plant,herbivore food webs, defined as turnover of trophic interactions between the food webs, represents a potentially useful extension of traditional studies of plant and herbivore beta diversity as it integrates spatial turnover of plant and herbivore species with changes in herbivore host plant preferences. 2Beta diversity of plant,herbivore food webs can be partitioned into four components, corresponding to the turnover of plant,herbivore interactions due to change in (i) both plant and herbivore species, (ii) plant, but not herbivore, species, (iii) herbivore, but not plant, species, and (iv) herbivore host preferences between food webs. These components can be quantified using a range of existing beta diversity indices. 3Relative magnitude of plant and herbivore beta diversity of plant,herbivore food webs can be analysed as an outcome of herbivore (i) host specificity, (ii) ability to track host plant populations by dispersal, and (iii) response to environmental conditions, competitors and enemies. The relative importance of these factors in tropical ecosystems remains to be determined. [source] Characterization of Fusarium verticillioides strains by PCR-RFLP analysis of the intergenic spacer region of the rDNAJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2006Belén Patiño Abstract Thirty-three Fusarium verticillioides strains from diverse origins and hosts have been analysed for fumonisin production and characterized in order (i) to detect the variability present in this species and (ii) to discriminate among isolates. The method used was a combination of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) generated by restriction endonucleases applied to the IGS region (intergenic spacer of rDNA). All the F. verticillioides strains associated with crops produced fumonisins B1 and B2 except those isolated from banana. Analysis of the IGS region by PCR-RFLP proved to be useful to detect variability within F. verticillioides and allowed discrimination of two related groups of isolates belonging to distinct lineages differing in fumonisin production and host preferences: the fumonisin-producing group associated with cereals and the fumonisin non-producing group associated with banana. The method used facilitates early detection and characterization of F. verticillioides strains required to control both types of pathogens and to evaluate plant exposure to the toxin, quality of the raw material to be processed and the potential fumonisin contamination in order to prevent fumonisins entering the food chain. Copyright © 2005 Society of Chemical Industry [source] Microsatellite analysis reveals strong but differential impact of a social parasite on its two host speciesMOLECULAR ECOLOGY, Issue 3 2006BIRGIT FISCHER-BLASS Abstract The speed and the dynamics of the co-evolutionary process strongly depend on the relative strengths of reciprocal selection pressures exerted by the interacting species. Here, we investigate the influence of an obligate social parasite, the slave-making ant Harpagoxenus sublaevis, on populations of the two main host species Leptothorax acervorum and Leptothorax muscorum from a German ant community. A combination of genetic and demographic data allowed us to analyse the consequences of raiding pressure on the hosts' life history and possible host preferences of the parasite. We can demonstrate that slave raids during which the social parasite pillages brood from neighbouring host colonies are both frequent and extremely destructive for both host species. Microsatellite analysis showed that, on average, a single slave-maker colony conducts more than three raids per year and that host colonies mostly perish in the aftermath of these parasite attacks. Only in few cases, surviving nests of previously raided host colonies were found in the surroundings of slave-maker colonies. As a consequence of the high prevalence of parasites and their recurrent and devastating slave raids on host colonies, the life expectancy of host colonies was severely reduced. Combining our results on host-specific parasitic colony founding and raiding frequencies with the post-raid survival rate, we can demonstrate an overall higher mortality rate for the smaller host species L. muscorum. This might be caused by a preference of H. sublaevis for this secondary host species as demographic data on host species usage indicate. [source] Relationship between saprotrophic growth in soil of different biotypes of Pochonia chlamydosporia and the infection of nematode eggsANNALS OF APPLIED BIOLOGY, Issue 1 2009I.A. Siddiqui Abstract The ecology of Pochonia chlamydosporia in soil and its interaction with both plant and nematode hosts are important for the successful exploitation of the fungus as a biological control agent. Differences in saprotrophism and parasitism were assessed for biotypes of P. chlamydosporia, which had originated from the eggs of cyst or root-knot nematodes. Colonisation in soils of different textures (compost, sandy loam and loamy sand) measured by the numbers of colony-forming units, differed greatly. Most biotypes were more abundant in sterilised soil of the different textures compared with non-sterilised soils. The proportion of nematode eggs parasitised in a baiting technique demonstrated that biotypes had host preferences. Those biotypes that originated from root-knot nematodes (RKN-biotypes) infected significantly more Meloidogyne hapla eggs than Globodera pallida eggs, whereas biotypes from cyst nematodes (CN-biotypes) parasitised more G. pallida eggs than M. hapla eggs. Differences in virulence between biotypes in an in vitro assay in which the fungi were placed directly onto the egg masses of M. hapla and those differences observed in the baiting technique showed similar trends. There was a negative linear correlation between the growth of the eight biotypes in soil and the proportion of eggs they infected in compatible interactions (i.e. fungal biotype originated from the same nematode genus as the target eggs). Those biotypes that infected most nematode eggs colonised soil the least extensively, suggesting that virulence may have a fitness cost. However, the relationship between saprotrophic growth and virulence is complex. The relative abundance of the different biotypes in soil in Petri dish assays was similar to that under glasshouse conditions using potato but not tomato as the plant host. Chlamydospores of some biotypes applied to soil significantly reduced (>50%) the population densities of M. hapla on tomato and of G. pallida on potato plants. Some biotypes that were both effective and virulent are good candidates for biological control of specific nematode pests. Data presented here and elsewhere indicate that RKN-biotypes have different host preferences to CN-biotypes; the specific primers based on the vcp1 gene from P. chlamydosporia rapidly confirmed the host origin of seven of the eight biotypes. [source] Divergent host plant adaptation drives the evolution of sexual isolation in the grasshopper Hesperotettix viridis (Orthoptera: Acrididae) in the absence of reinforcementBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2010TONY GRACE Early stages of lineage divergence in insect herbivores are often related to shifts in host plant use and divergence in mating capabilities, which may lead to sexual isolation of populations of herbivorous insects. We examined host preferences, degree of differentiation in mate choice, and divergence in cuticular morphology using near-infrared spectroscopy in the grasshopper Hesperotettix viridis aiming to understand lineage divergence. In Kansas (USA), H. viridis is an oligophagous species feeding on Gutierrezia and Solidago host species. To identify incipient mechanisms of lineage divergence and isolation, we compared host choice, mate choice, and phenotypic divergence among natural grasshopper populations in zones of contact with populations encountering only one of the host species. A significant host-based preference from the two host groups was detected in host-paired feeding preference studies. No-choice mate selection experiments revealed a preference for individuals collected from the same host species independent of geographic location, and little mating was observed between individuals collected from different host species. Female mate choice tests between males from the two host species resulted in 100% fidelity with respect to host use. Significant differentiation in colour and cuticular composition of individuals from different host plants was observed, which correlated positively with host choice and mate choice. No evidence for reinforcement in the zone of contact was detected, suggesting that divergent selection for host plant use promotes sexual isolation in this species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 866,878. [source] | |||||||||||||||||||||||||||||||