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  • 1
    Electronic Resource
    Electronic Resource
    Fish predation and reduction in body size in a Cladoceran population: palaeoecological evidence (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 21 (1989), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1 We studied the recent history (1852-1982) of Lake Pyhä-järvi, south-west Finland, using both cladoceran microfossils and independent historical data. The objective of the study was to assess the impact of introduced planktivorous whitefish Coregonus lavaretus s.1. on zooplankton, especially on the main prey species Bosmina coregoni Baird s.str.2. A size-frequency analysis of carapace remains preserved in the sediments clearly shows a size shift in a Bosmina coregoni population. The carapace length of B. coregoni decreased by 11.0% after the introduction of the size-selective planktivorous whitefish, indicating a parallel body-size reduction.3.During the study period no changes could be found in the carapace length of Chydorus sphaericus O. F. Müller, which was not preyed upon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1989.tb01360.x
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  • 2
    Electronic Resource
    Electronic Resource
    Sensitivity of Daphnia to toxic cyanobacteria: effects of genotype and temperature (1997)
    Oxford BSL : Blackwell Science Ltd
    Freshwater biology 37 (1997), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. We studied the effects of both acute and chronic exposure of Daphnia pulex to toxic Microcystis aeruginosa. We focused on the effects of Daphnia genotype and temperature (19 and 24 °C).2. The study revealed variation among ten Daphnia pulex clones in survivorship under acute Microcystis exposure, measured as EC50. An increase in temperature caused a clear decrease in EC50, although the ranking of clones according to sensitivity remained the same at both temperatures.3. In the chronic exposure of two of the clones, toxic Microcystis reduced survival and reproduction. The two clones differed in their responses, indicating different means of coping with toxic cyanobacteria. Toxic cyanobacteria reduced slightly more at 24 °C than 19 °C.4. The clonal difference in sensitivity to toxic cyanobacteria at acute exposure was reversed at chronic exposure. This indicates that the results from short-term toxicity cannot be used to predict life history responses under sublethal exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1997.d01-555.x
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  • 3
    Electronic Resource
    Electronic Resource
    Herbivore-induced resistance in Betula pendula: the role of plant vascular architecture (1996)
    Springer
    Oecologia 108 (1996), S. 723-727 
    Details
    ISSN: 1432-1939
    Keywords: Herbivory ; Betula pendula ; Induced resistance ; Phyllotaxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the role of plant vascular architecture in the determination of the spatial extent of herbivore induced responses within Betula pendula Roth saplings. The induced responses were measured in bioassays in terms of the relative growth rate of larvae of a geometrid moth, Epirrita autumnata. We hypothesised that the level of induced resistance of a certain leaf would be determined by the degree of vascular connectivity between the leaf in question and a damaged leaf, as suggested by recent theoretical and empirical studies. A comparison of the control plants with the damaged plants indicated that damaging one leaf of a sapling was sufficient to induce an increase in the resistance level. There were also differences among the leaves within a plant in the resistance level, but these differences could not be explained by the degree of vascular connectivity with the damaged leaf. These results suggest that the vascular connections have low power as explanations of the spread and spatial extent of the induced resistance in Betula pendula saplings Instead, the resistance level of all leaves within a sapling increased following the damage. We suggest that the pattern of increased resistance observed in this experiment may be beneficial for the young saplings studied. For young saplings at their early stages of development, it may be beneficial to be able to distribute the induction signal to all leaves as fast as possible and thus repel the herbivore totally. For a young sapling, the capability of repelling the herbivore totally might thus be a feasible strategy whereas an older sapling may tolerate localised damage better and compensate for the damage within the undamaged plant parts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329048
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  • 4
    Electronic Resource
    Electronic Resource
    Growth, reproduction and defence in nettles: responses to herbivory modified by competition and fertilization (1995)
    Springer
    Oecologia 104 (1995), S. 487-495 
    Details
    ISSN: 1432-1939
    Keywords: Urtica spp ; Cost of defence ; Compensatory continuum ; Competition ; Fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the effects of environmental factors on the ability to compensate for simulated herbivory in an annual (Urtica urens) and two perennial (U. dioica subspp. dioica and sondenii) nettle species in order to test the compensatory continuum hypothesis. Further, we studied the expression of costs of structural defence in different environmental conditions. Herbivory interacted significantly with density and fertilization for height growth, branching and reproductive traits. The negative effects of simulated herbivory on relative height growth were less detrimental for plants grown in low density and high fertilization level, which supports the compensatory continuum hypothesis. However, with respect to other traits measured, our results do not support the idea of compensatory continuum. The negative effects of apical excision on inflorescence biomass were relatively more prominent in plants growing at low density and receiving more fertilization than on those growing in worse conditions. In addition, branching was reduced by apical excision regardless of resource levels. The lack of compensation for herbivory is explained by the role which the damaged or removed tissue plays in plant development and function. In the perennial U. dioica, defensive responses to herbivory, measured as changes in trichome density, were stronger than in the annual U. urens. In the southern subspecies dioica, trichome density increased in newly emerged leaves after leaf clipping. In the northern subspecies sondenii, trichome density increased after apical excision. The differences in the defensive responses between the two subspecies of U. dioica may be due to differential natural herbivory pressures on subspecies inhabiting different geographical regions. We observed negative phenotypic correlations between structural defence and other plant traits, which suggests the existence of costs of defence. In addition to differences among the species studied, the expression of costs of defence was dependent on the resource levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341346
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  • 5
    Electronic Resource
    Electronic Resource
    Gall mite (Eriophyes laevis) infestation and leaf removal affect growth of leaf area in black alder (Alnus glutinosa) short shoots (1990)
    Springer
    Oecologia 84 (1990), S. 122-125 
    Details
    ISSN: 1432-1939
    Keywords: Herbivory ; Gall mite ; Eriophyes laevis ; Alnus glutinosa ; Leaf growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We measured the effects ofEriophyes laevis mite galls on the relative growth of short shoot leaf area ofAlnus glutinosa. A portion of leaves was artificially removed from a set of short shoots with both high and low gall density to cause local stress conditions. Nontreated high and low gall density short shoots were used as controls. The results show that the relative growth of leaf area measured for short shoots is negatively affected by high gall density. Artificial leaf removal, on the other hand, had positive effects on leaf area growth. Interestingly, the growth of leaf area did not differ for high gall density short shoots with leaf removal and noninfested short shoots with no leaf removal. This result may be caused by the combined, opposite effects of leaf removal and gall infestation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665605
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  • 6
    Electronic Resource
    Electronic Resource
    Demographic costs of Chaoborus-induced defences in Daphnia pulex: a sensitivity analysis (1991)
    Springer
    Oecologia 87 (1991), S. 43-50 
    Details
    ISSN: 1432-1939
    Keywords: Predator-prey interaction ; Inducible defence ; Population growth ; Daphnia pulex ; Chaoborus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We examined the demographic costs of Chaoborus-induced defensive spine structures in Daphnia pulex. Our aim was to assess the role of resource limitation and the interaction effects of limiting food level and antipredator structures on fitness of D. pulex and to pinpoint those life stages that are most sensitive to changes in the defence regime. Chaoborus-induced and typical morphotypes of D. pulex were reared at high and low food concentrations. Instar-based matrix population models were used to quantify the effects of predator-induction, food and their interaction on fitness of D. pulex. Predator-induction caused a statistically significant reduction in fitness at low food levels, but not at high food levels. Sensitivity analyses revealed that the fitness effects were primarily due to changes in the growth rate in instars 1–5, and secondarily to small reductions in the fertility of instars 5–10. The interaction between Chaoborus exposure and low food concentration was negative, and mediated through growth and fertility components. Both these components were reduced more in the Chaoborus-exposed, low food treatment than would be expected in the absence of interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323778
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  • 7
    Electronic Resource
    Electronic Resource
    Consequences of herbivory in the mountain birch (Betula pubescens ssp tortuosa): importance of the functional organization of the tree (1990)
    Springer
    Oecologia 82 (1990), S. 238-247 
    Details
    ISSN: 1432-1939
    Keywords: Apical dominance ; Induced defence ; Induced amelioration ; Epirrita autumnata ; Modularity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three types of experiments indicate that the functional organization of the mountain birch may influence the ways in which the tree responds to simulated or natural herbivory. The first experiment showed that herbivory to both short and long shoot leaves affects plant development but, because growth largely proceeds by resources of the previous year, is manifested only in the year following the damage. The second experiment showed that even partial damage to a single long shoot leaf caused the axillary bud of that leaf to produce a shorter shoot the next year. Therefore, the value of a leaf depends also on the organ which it is subtending. In the third experiment we manipulated the apical dominance of shoots in ramets and caused improvement to leaf quality in extant shoots. Ramets within a tree responded individually, probably mediated by disturbance of the hormonal control because removal of apical buds elicited the response although removal of the same number of basal buds did not. Induced amelioration is a different response to induced resistance. The two responses are triggered by different cues and may occur in the same plant. By altering hormonal balance of shoots it is potentially possible for herbivores to induce amelioration of food quality. The ways in which herbivory is simulated may explain variability of results obtained when herbivory-induced responses in plants have been studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323540
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  • 8
    Electronic Resource
    Electronic Resource
    Management of biodiversity: natural resources and social institutions (1999)
    Springer
    Biodiversity and conservation 8 (1999), S. 1-6 
    Details
    ISSN: 1572-9710
    Keywords: biodiversity ; decision making ; management ; natural resources ; social institutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008874120543
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  • 9
    Electronic Resource
    Electronic Resource
    Variation in the neonate size of Daphnia pulex: the effects of predator exposure and clonal origin (1998)
    Springer
    Aquatic ecology 32 (1998), S. 203-209 
    Details
    ISSN: 1573-5125
    Keywords: Chaoborus ; clones ; Daphnia ; life history ; ponds ; predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Daphnia pulex clones originating from twelve small pond habitats were exposed to chemical cues from a size-selective predator, larvae of the phantom midge Chaoborus. Exposure delayed the onset of reproduction and increased the size at first reproduction. On the other hand, the neonates produced by these larger mothers were slightly smaller than the neonates produced by the smaller control mothers. In cladocerans, neonate size is usually positively correlated to the size of the mother. Thus exposure to Chaoborus kairomone apparently had direct effects on neonate size counterbalancing the maternal effects. Daphnia clones collected from Chaoborus-free and Chaoborus-rich environments exhibited different responses. In first adult instar, the clones from Chaoborus inhabited environments increased their offspring size under Chaoborus exposure whereas clones from Chaoborus-free environments did not. This may reflect clonal adaptation to the predation prehistory of their original habitat since larger neonates more quickly reach a size protected from the predator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009978527633
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  • 10
    Electronic Resource
    Electronic Resource
    Specificity of predator-induced neck spine and alteration in life history traits in Daphnia pulex (1994)
    Springer
    Hydrobiologia 294 (1994), S. 129-140 
    Details
    ISSN: 1573-5117
    Keywords: induced defence ; Daphnia pulex ; invertebrate predators ; life history ; cost of defence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has been proposed that the predator-induced defensive neck spine in Daphnia pulex has a demographic cost. Our results show that this cost is not merely an allocation cost related to the formation and maintenance of the neck spine. In a life table experiment, we tested whether spine induction and life history traits in D. pulex are affected by different invertebrate predators: first and third instar Chaoborus, fourth instar Mochlonyx and two size classes of Notonecta and Dytiscus larvae. D. pulex showed sensitivity to the different predators. Predator-exposure affected one or more of the following life history traits of D. pulex: the timing of first reproduction, clutch size, and growth. In some cases, exposure to predators altered life history traits when neck spine induction did not occur. These shifts in life history traits occurring in the absence of spine induction may be caused by behavioral or physiological changes triggered by the predators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016853
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