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  • 1
    ISSN: 1573-8248
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Nous proposons ici des méthodes en vue d’une approche théorique du choix et de l’introduction d’Insectes entomophages. Une fois établis les besoins nécesaires aux organismes pour leur reproduction et leur survie, on choisit des sites afin d’échantillonner les Insectes en fonction des degrés d’un certain facteur critique. Quelle que soit la forme des gradients utilisés la répartition des échantillons doit être représentative des composantes du milieu. La distribution des entomophages d’après ces composantes est anlysée et quantifiée au moyen d’une formule qui montre l’aire de distribution d’un espèce, la similitude entre les distributions, et l’interaction à laquelle chaque espèce devra faire face dans chacun des groupes de composantes. Ces calculs peuvent être d’une grande utilité dans le choix de la meilleure espèce à introduire dans une région dont on connaît la composition et la distribution des espèces.
    Notes: Abstract Methods are proposed as a contribution towards the formalization of an approach to the selection and introduction of entomophagous insects. Once the critical resources necessary for the reproduction and survival of a predator or parasitoid have been identified, sites are arranged to sample these insects in different grades of the same critical factor. These grades of a resource may be ranked, and organized on gradients, or unranked, but in both cases the range of samples represents a resource set. The entomophagous insect distributions on these sets are analyzed and quantified by formulae that show the breadth of a species distribution, the similarity between distributions, and the interaction species will experience on each of the resource sets. These calculations can assist in selecting the best species for introduction into an area with a known species composition and distribution.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 73 (1987), S. 334-337 
    ISSN: 1432-1939
    Keywords: Euura mucronata ; Bud galler ; Herbivore ; Plant age ; Salix cinerea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary As ramets of the willow, Salix cinerea L. (Salicaceae) aged shoot length decreased in the six populations studied in S.E. Finland. Many traits correlated positively with shoot length: basal diameter, number of internodes, internode length, leaf size, and length of growing period. The bud-galling sawfly, Euura mucronata (Hartig) Man. (Churchill) (Hymenoptera: Tenthredinidae), responded positively to shoot length or correlated traits, and negatively to ramet age in three forest populations. This herbivore attacked the most vigorous plants in a population, and numbers of attacks declined as ramets aged and senesced. The generality of this kind of herbivore response to plant quality is emphasized.
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  • 3
    ISSN: 1432-1939
    Keywords: Herbivore survival ; Plant/insect interactions ; Plant quality ; Salix cinerea ; Shoot length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The bud-galling sawfly, Euura mucronata, attacked longer shoot length classes on its host, Salix cinerea, more frequently than shorter shoots. Shoot length accounted for 76 to 93 percent of the variance in number of galls per 100 shoots in three habitats: forest, watermeadow, and lakeside. The reasons for this pattern were addressed with studies on shoot length in relation to: 1. Number of resources (buds) per shoot; 2. Success in establishment of larvae in galls; 3. Gall size and resources per gall; and 4. Survival of larvae after establishment as influenced by plant resistance and natural enemy attack. The most important factors proved to be success in establishment of larvae, with percent of variance accounted for ranging from 57 to 77 percent in three of four sites where relationships were significant, and survival after establishment of larvae, with variance accounted for ranging from 40 to 54 percent in the same three sites. The pattern of survival was dictated by plant resistance and not by natural enemies. These two additive factors resulted in a general relationship across all sites of increasing emergence of fully developed larvae per cohort as shoot length increased, accounting for 78 percent of the variance. These adaptive advantages to attacking longer shoots are sufficient to account for the pattern of increased probability of shoots being attacked as they increase in length.
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  • 4
    ISSN: 1432-1939
    Keywords: Phylloxera ; Grape ; Local adaptation ; Deme ; Interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We tested the deme-formation hypothesis experimentally with four populations of leaf-galling grape phylloxera, Daktulosphaira vitifoliae, and its host, canyon grape (Vitis arizonica). An experiment designed to examine preference and performance showed that phylloxera populations did not significantly prefer their original host relative to other hosts in the percent available leaves galled. There were significant herbivore population effects (P〈0.01), host effects (P〈0.001), and population x host interaction effects (P〈0.001). Herbivore populations had different colonizing abilities (performance, as measured in the mean number of galls per leaf) on an individual host (P〈0.001), but there was no host effect. Host genotype significantly affected phylloxera performance, measured as survivorship (P〈0.01), but a phylloxera population did not necessarily have higher survivorship on its original host. Differences in fecundity, an-other measurement of performance, were due to intrinsic differences among herbivore populations (P〈0.05), and not related to host genotype. There was no correlation between distance from a phylloxera population in the field and a host's susceptibility to attack. There was a significant positive relationship between levels of infestation on a clone in the field and its susceptibility to colonization experimentally (P〈0.05), suggesting inherent differences in host resistance and susceptibility. These results did not support the deme-formation hypothesis. In a second experiment, host clone x water treatment interactions affected phylloxera survivorship (P〈0.05) and fecundity (P〈0.05). We conclude that host genotype x environment interactions may prevent sessile, parthenogenetic herbivores from locally adapting to individual host genotypes.
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  • 5
    ISSN: 1432-1939
    Keywords: Community structure ; Host plant variation ; Gall-forming sawflies ; Willow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The densities of four species of gall-forming sawflies were found to vary significantly among willow host plant clones. Two of the speices varied among host plants at four sites in each of three years. The other two species varied in density among host plants at most of the sites in two of the three years. Total sawfly density also varied significantly among clones. Individual species densities on willow clones were significantly positively correlated between years when all sites were combined and frequently when sites were considered separately. Most pairwise species combinations were independent in density between years, but some negative correlations existed between the stem galler and the leaf galler. Gall-former densities also were largely independent among clones within years with all sites combined and with sites considered separately. The significant correlations were nearly all positive. At all four sites the combination of significant variation in sawfly densities among willow clones in the field and independence of species densities among clones resulted in significantly different communities (relative abundance of species) among willow clones in three years. Although sawfly abundances differed substantially among the four sites, this remained true. It is argued that the pattern of community structure among clones is the result of variation in host plant quality of clones. We propose an hypothesis to account for patterns of herbivore species associations based on intrapopulation host plant variation.
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  • 6
    ISSN: 1432-1939
    Keywords: Community structure ; Galls ; Insect-plant interactions ; Plant variation ; Sawflies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four species of gall-forming sawflies were each frequently found to have clumped distributions among shoots within their willow host plant across four sites and three years. When all species were considered together by clone, year, and site, species showed independence of distribution among shoots two thirds of the time and showed positive covariance one third of the time. When pairs of species were considered separately, but clones were combined within sites and years, 60% of the chi-square tests of association were significant. All but one of the significant tests showed positive associations between pairs of species. The stem galler was positively associated with the leaf folder at all sites in all years, and the petiole galler was positively associated with the stem galler and leaf folder for most year by site combinations. When species paris co-occurred on shoots they were usually found at the same or higher density as when found alone on shoots. Only 2 of 100 tests showed a depressed density of a species when co-occurring on shoots with heterospecifics. All sawfly species were found on shoots that were significantly larger (mean node number) than on shoots without sawflies, and species responded to shoot size variation similarly. Sizes of shoots occupied by heterospecific species combinations were usually significantly larger than shoots with only conspecifics, for all species. These data supported the hypothesis that similar species' responses to within-plant variation would lead to positive rather than negative or random species associations. The data do not support the hypothesis that interspecific competition was important in determining shoot choice or species density.
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  • 7
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
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  • 8
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
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