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  • Community structure  (2)
  • Grape  (1)
  • Phylloxera  (1)
  • Sawflies  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Variability in grape phylloxera preference and performance on canyon grape (Vitis arizonica) (1996)
    Springer
    Oecologia 107 (1996), S. 553-559 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333948
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  • 2
    Electronic Resource
    Electronic Resource
    Variation in herbivore density among host plants and its consequences for community structure (1987)
    Springer
    Oecologia 72 (1987), S. 577-588 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378986
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  • 3
    Electronic Resource
    Electronic Resource
    Patterns of intra- and interspecific association of gall-forming sawflies in relation to shoot size on their willow host plant (1987)
    Springer
    Oecologia 73 (1987), S. 159-169 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377503
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