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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 56 (1934), S. 584-585 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Pty
    Austral ecology 28 (2003), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  In this work, we investigated the spatial distribution of two sessile insect herbivores over the entire range of their host plant, Coccoloba cereifera, a sclerophyllous shrub endemic to Serra do Cipó, Brazil. The two insects have very distinct life histories and dispersal behaviours and we hypothesized that their classification into behavioural syndromes could be used to predict their spatial distribution patterns. Abgrallaspis cyanophylli (Homoptera) is an armoured scale insect that fits well into the eruptive syndrome. Stenapion aff. contrarium (Coleoptera) is a petiole borer with wide search capabilities, which fits into the latent syndrome. We expected that Abgrallaspis would follow the host plant aggregation pattern whereas Stenapion would be distributed more uniformly through the region and be less affected by host aggregation. We counted the number of attacked and non-attacked ramets within two perpendicular belt transects as well as within a 20 m × 20 m quadrat placed over a dense shrub aggregation. Local quadrat covariance methods were used to estimate the spatial pattern of each insect. At fine scales, we found Stenapion evenly distributed over the host plant and Abgrallaspis with a significantly aggregated pattern. This finding is in accordance with our hypothesis. At larger scales, however, this pattern was lost and the results were largely variable. We conclude that the classification of insects into behavioural syndromes may be useful to predict distribution patterns at fine scales. At larger scales, however, history and chance events may be more important.
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  • 3
    Electronic Resource
    Electronic Resource
    Melbourne, Australia : Blackwell Science Asia Pty. Ltd.
    Austral ecology 26 (2001), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The response of a host plant to gall-inducing insects varies both among and within plants, so that different levels of resources are available to the insects. The weevil Collabismus clitellae Boheman induces galls on the shoots of Solanum lycocarpum St Hil. in south-east Brazil. Galls are found on a range of parts within an individual plant and are more abundant on smaller plants. In the present study, the host plant response as a possible influence on the performance of C. clitellae both between and within plants was tested. Gall abortion increased with plant height. Within plants, gall size was positively related to shoot diameter and number of chambers within the gall. The increase in gall larval density (number of individuals per gall volume unit) resulted in smaller adults and reduced developmental rates, probably because of resource limitation within the gall. The number of eggs laid by females increased with shoot diameter. Females laid more eggs on thicker shoots, where there are fewer chances to form galls with high larval density. However, this relationship was weak and a large variation was found for adult sizes. The availability of high quality sites is limited to smaller plants and thicker shoots located on the basal region of the plant. The phenotypic plasticity of this insect species in adult size and development time allows individuals growing on low quality sites to reach maturity, thus enhancing exploitation of the host plant.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Austral ecology 27 (2002), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this study, the mortality factors acting upon the galling psyllid Neopelma baccharidis Burckhardt (Homoptera) caused by its host plant, Baccharis dracunculifolia De Candole (Asteraceae) were analysed. In March 1999, 982 galls of the same cohort were randomly marked on 109 individuals of B. dracunculifolia in the field. Galls were censused each month during their development, from April to August, and dead galls were collected and analysed for mortality factors. Gall dehiscence rates were calculated for each month. The major mortality source of N. baccharidis was gall dropping (13.2% of the original cohort), which is probably a normal outcome of previous mortality caused by the other factors observed in this study. Unknown factors killed 11.7% of this gall population and were ascribed to plant resistance during gall development. Empty galls represented 7.7% of the observed mortality and may be a consequence of egg retention or egg mortality/abortion related to variations in plant quality. Shoot mortality was high during the dry season and killed 7.5% of the galls, but this impact was minimized after the third month from gall formation due to the ability of nymphs to accelerate development and emerge from galls on dying shoots. However, the size of dehisced galls on dead shoots tended to be smaller, possibly affecting adult performance. Mortality of N. baccharidis attributed to B. dracunculifolia strongly controlled the galling insect population, killing 40.7% of the original cohort of galls. Plant-mediated mortality was caused by often neglected factors acting predominantly during the first 3 months of development, which are critical to gall survivorship. These results reinforce the importance of bottom-up forces in plant-insect systems.
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  • 5
    Electronic Resource
    Electronic Resource
    Melbourne, Australia : Blackwell Science Pty
    Austral ecology 26 (2001), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Herbivory in natural communities can be high, reducing the growth and reproduction of individual plants. To diminish the impact of herbivores, plants use a variety of defensive mechanisms. It is now recognized that the plant world is characterized by a proliferation of secondary metabolites, but models of the evolution of defence strategies assume that plants are constrained by finite resources, and that defences are costly. In the present study, the relationships between defence, growth and nutrient concentration in Bauhinia brevipes Vog. (Leguminosae) in south-eastern Brazil were investigated. Patterns of herbivory and defence were examined for 170 B. brevipes individuals in 1997 and 1998. Leaf age influenced tannin concentration and herbivore attack on B. brevipes. Mature leaves had higher concentrations of tannins than young leaves, and young leaves were approximately 60% more likely to be attacked than mature leaves. Carbon and nitrogen content explained 36% of the variation in the percentage of attacked leaves in B. brevipes (y = 16.29 – 0.31 C + 0.25 N; r2 = 0.36; F = 9.56; P 〈 0.0001). Tannins acted as defensive compounds on B. brevipes leaves against free-feeding herbivores, but no clear pattern was observed against galling herbivores. The amounts of nitrogen, carbon, potassium, and aluminium explained approximately 69% of the variation in tannin concentration on B. brevipes leaves (y = 0.62 – 0.16 N – 0.36 K – 0.26 Al + 0.74 C; r2 = 0.69; F = 21.18; P 〈 0.0001). We found an inverse relationship between shoot growth rates and tannin concentration in B. brevipes, indicating that the production of tannins may be costly, therefore offering some evidence for the trade-off hypothesis. Nevertheless, the weak relationship observed between herbivore damage and tannin concentration indicates that other factors are also involved with herbivore pressure.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 54 (1952), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1939
    Keywords: Plant systematics ; Discriminant function analyses ; Taxonomy ; Arizona
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Within a population of rubber rabbitbrush, Chrysothamnus nauseosus, the subspecies C. nauseosus consimilis and C. nauseosus hololeucus, and a third unidentified group were better segregated by their insect galls, than by differences in plant morphology. This level of segregation was further increased when morphological measurements and counts of insect galls were analyzed simultaneously. We interpret this result to mean that plant morphology and insect distributions reflect two different, perhaps overlapping, portions of the host's genome. By using both sets of characters concurrently, rather than either set independently, we increased the portion of the plant's genome being sampled and increased the probability of detecting differences among host genotypes. Hence, knowledge of the distributions of insect galls may be useful for augmenting the level of separation, obtained by morphological measurements, among intrapopulational categories of plant genotypes. This application may be of greatest benefit when hybridization blurs morphological distinctions among plant taxa, when morphological traits are highly variable within genotypes, or when ephemeral morphological traits (e.g., leaves, flowers) are not available for measurements.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 76 (1988), S. 161-167 
    ISSN: 1432-1939
    Keywords: Adaptation ; Altitudinal gradients ; Herbivores ; Insect galls ; Species richness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five hypotheses were invoked to account for variation in galling species number per location on plants of different structural complexity, namely herbs, shrubs, and trees, both in Brazil and USA. The hypotheses were: 1) the altitudinal/latitudinal gradient hypothesis; 2) the harsh environment hypothesis; 3) the plant species richness hypothesis; 4) the host plant area hypothesis; 5) the plant structural complexity hypothesis. The altitudinal and the harsh environment hypotheses were correlated and supported with sample data in both localities, with increasing gall species number as altitude/latitude declined and as sites became hotter and drier. The two hypotheses were separated by studying riparian sites and dry hillside sites at the same elevation in Arizona. Galling species frequency was higher in dry sites than in riparian sites, supporting the harsh environment hypothesis. Of the five hypotheses tested only the harsh environment hypothesis predicted that galling insect species number should vary in response to environmental variables such as moisture and temperature. Temperate shrubs supported more galling species than did other plant types, both in dry and mesic sites. The overall difference between galling species richness for tropical and temperate latitudes was not statistically significant. Free-feeding insect herbivore species exhibited the opposite pattern of species richness to gallers, being more speciose in riparian sites. The present study corroborates the hypothesis that the gall forming habit is an adaptation to harsh or stressful environments, and we describe for the first time broad scale geographical patterns in galling insect species richness.
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  • 9
    ISSN: 1432-1939
    Keywords: Adaptations ; Habitat selection ; Herbivore survivorship ; Insect distribution ; Insect galls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied the relationship between habitat moisture and gall-forming insect populations. Population sizes for most galling taxa were significantly larger in xeric habitats compared with mesic habitats. Our results indicate that the differential abundance of galling insects in these habitats is due primarily to differential mortality and survivorship. Mortality factors acting upon eight insect galling species (belonging to eight genera and four families) were measured on six species (five genera and five families) of host plants. Survival was significantly higher for galling populations inhabiting xeric habitats compared with mesic habitats. Parasitism was higher in mesic habitats in seven of eight habitats and fungus-induced diseases were higher in five of seven habitats. Mortality due to predation and other (unknown) factors showed no clear trends. Overall, there was a tendency towards lower mortality and consequently higher survival for populations inhabiting xeric habitats. We hypothesize that reduced mortality caused by natural enemies and endophytic fungi has contributed to the speciation and radiation of galling insects in apparently harsh environments.
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  • 10
    ISSN: 1572-9753
    Keywords: altitudinal gradient ; cerrado ; free-feeding insect herbivores ; high altitude grassland vegetation ; sclerophylly.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Abstract The distribution of free-feeding insect herbivores in Brazilian savanna was studied in the National Park of Serra do Cipó. Insect samples were obtained with sweep nets across cerrado (savanna), rupestrian field and altitudinal grassland vegetation from 800 to 1500 m above sea level. We found a low species richness in xeric and mesic habitats during both wet and dry seasons. Sap-sucking insects were the most abundant guild (53.4%) with Cicadellidae the most abundant family (27.2%). The hypothesis that taxon richness of free-feeding insects decreases with increasing altitude was supported in xeric habitats during the wet season only, mainly as a function of mountain summit effect. There was a decrease of 65% in the number of families occurring at 1400 and 1500 m compared with lower elevations. The exclusion of sites of rupestrian vegetation at mid-elevations from the analysis increased significantly the proportion of variance explained by the model. An examination of taxon distribution using canonical variate analysis supported this result. The hypothesis that mesic habitats are richer in species of free-feeding insect herbivores than are xeric habitats was not supported. The data indicate that plant sclerophylly may exert a strong negative influence on insect species richness, and that variation due to particular characteristics of each site strongly affected the studied guilds. The present results should inform conservation strategies for the National Park Management Plan, which is currently being developed. © Rapid Science Ltd. 1998
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