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  • 1
    Electronic Resource
    Electronic Resource
    Effects of host plant hybridization on resistance to willow leaf rust caused by Melampsora sp. (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Forest pathology 28 (1998), S. 0 
    Details
    ISSN: 1439-0329
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Patterns of resistance to willow leaf rust caused by Melampsora sp. were measured on Salix eriocephala, Salix sericea, and their interspecific hybrids in natural field populations in 1991–94 and on potted plants in common garden experiments in 1994 and 1995. Testing was carried out to establish if the resistance of hybrids was intermediate between pure parental species (additive), equal to one of the parents (dominant), lower than both parents (susceptible), higher than both parents (resistant), or not different than either parent (null hypothesis). Support was generally found for hybrid susceptibility in the field and common garden experiments, with the null hypothesis of no difference having some support. The results from the common garden study suggest that the susceptibility of hybrids seen in the field is due to genetic differences. Hybridization between these species of willows results in increased susceptibility to this pathogen. The variation among years in the relative susceptibility of hybrid and parental willows may be due to environmental effects on the willows or to shifts in the abundance of Melampsora races.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0329.1998.tb01181.x
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  • 2
    Electronic Resource
    Electronic Resource
    Parasite Mediation in Ecological Interactions (1986)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 17 (1986), S. 487-505 
    Details
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.es.17.110186.002415
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  • 3
    Electronic Resource
    Electronic Resource
    Interspecific hybridization of plants and resistance to herbivores: hypotheses, genetics, and variable responses in a diverse herbivore community (1994)
    Springer
    Oecologia 97 (1994), S. 106-117 
    Details
    ISSN: 1432-1939
    Keywords: Hybridization ; Herbivores ; RAPD ; Host plant resistance ; Willow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the morphology, molecular genetics, and hebivory of two species of willows (Salix sericea and S. eriocephala) and their interspecific hybrids to test four alternative hypotheses concerning the effects of hybridization on plant resistance. Individually marked plants were identified using morphological traits in the field and measurements of stipule and leaf pubescence were made and compared using Canonical Discriminant Function Analysis. DNA was extracted from the leaves of a sample of the marked plants and RAPD-PCR analysis was performed to establish the genetic status of parental and hybrid plants. RAPD band analysis generally verified the genetic status of parental plants. Hybrid plants were usually correctly identified in the field with a few exceptions. However, the hybrid plants were a heterogeneous group of plants made up of most plants that appear to be F1s and a few plants that appear to be backcrosses to S. sericea. Morphological variables were useful for distinguishing S. sericea from S. eriocephala and hybrids, but were not as dependable in distinguishing between S. eriocephala and hybrids. We compared the densities of 11 herbivore species and the infection by a leaf rust pathogen (Melampsora sp.) on the leaves and stems of two parents and the hybrids in the field. We found support for the Additive hypothesis (3 species), the Dominance hypothesis (2 species) and the Hybrid Susceptibility hypothesis (7 species, 6 herbivores and the Melampsora rust). We found no evidence for the Hybrid Resistance hypothesis. Guild membership was not a good predictor of similar responses of species to hybrid versus parental plants. A Canonical Discriminant Function Analysis showed discrete separation of the taxa based on herbivore densities, illustrating different community structures on hybrid and parental plants. This study demonstrates the diversity of responses of phytophages in response to interspecific hybridization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317914
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  • 4
    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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  • 5
    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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