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301.
Lars?GutowEmail author Jeremy?D.?Long Osvaldo?Cerda Ivan?A.?Hinojosa Eva?Roth?usler Fadia?Tala Martin?Thiel 《Marine Biology》2012,159(1):141-149
Many small marine herbivores utilize specific algal hosts, but the ultimate factors that shape host selection are not well
understood. For example, the use of particular microhabitats within algal hosts and the functional role of these microhabitats
have received little attention, especially in large algae such as kelps. We studied microhabitat use of the herbivorous amphipod
Peramphithoe femorata that inhabits nest-like domiciles on the blades of giant kelp Macrocystis pyrifera. The vertical position of nest-bearing blades along the stipe of the algal thallus and the position of the nests within the
lateral blades of M. pyrifera were surveyed in two kelp forests in northern-central Chile. Additionally, we conducted laboratory and field experiments
to unravel the mechanisms driving the observed distributions. Peramphithoe femorata nests were predominantly built on the distal blade tips in apical sections of the stipes. Within-blade and within-stipe feeding
preferences of P. femorata did not explain the amphipod distribution. Amphipods did not consistently select distal over proximal blade sections in habitat
choice experiments. Mortality of tethered amphipods without nests was higher at the seafloor than at the sea surface in the
field. Nests mitigated mortality of tethered amphipods, especially at the seafloor. Thus, protective microhabitats within
thalli of large kelp species can substantially enhance survival of small marine herbivores. Our results suggest that differential
survival from predation might be more important than food preferences in determining the microhabitat distribution of these
herbivores. 相似文献
302.
Ciannelli L Knutsen H Olsen EM Espeland SH Asplin L Jelmert A Knutsen JA Stenseth NC 《Ecology》2010,91(10):2918-2930
Until the last decade it was assumed that most marine species have pronounced gene flow over vast areas, largely because of their potential for dispersal during early life stages. However, recent genetic, modeling, and field studies have shown that marine populations may be structured at scales that are inconsistent with extensive dispersal of eggs and larvae. Such findings have stimulated the birth of new studies explaining the mechanisms that promote population structure and isolation in the oceans, in the face of high potential for dispersal. Here we study the vertical and horizontal distribution of cod (Gadus morhua) eggs in relation to small-scale circulation and water column hydrography in a coastal location of southern Norway. Previous studies conducted in this region have shown that cod populations inhabiting fjord locations, which are on average 30 km apart, are genetically differentiated, a remarkable outcome considering that Atlantic cod have pelagic egg stages and long pelagic larval duration. We document that cod eggs are found in greater abundance in shallow water layers, which on average are flowing up the fjord (away from the open ocean), and in the inner portion of the fjord, which is subject to lower current speeds compared to the outer or mouth of the fjord. Eggs were found to be neutrally buoyant at shallow depths, a trait that also favors local retention, given the local circulation. The same patterns held during two environmentally contrasting years. These results strongly suggest that population structure of Atlantic cod is favored and maintained by a balance between water circulation and egg characteristics. 相似文献
303.
Joakim Hjältén Anna Lindau Anders Wennström Patrik Blomberg Johanna Witzell Lars Ericson 《Chemoecology》2008,18(4):227-231
Summary. There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available.
However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been
explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can
influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two
lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in
sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the
isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments.
The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the
concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed
slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the
different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore
response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian
herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees. 相似文献
304.
Colony nutritional status modulates worker responses to foraging recruitment pheromone in the bumblebee Bombus terrestris 总被引:2,自引:1,他引:1
Mathieu Molet Lars Chittka Ralph J. Stelzer Sebastian Streit Nigel E. Raine 《Behavioral ecology and sociobiology》2008,62(12):1919-1926
Foraging activity in social insects should be regulated by colony nutritional status and food availability, such that both
the emission of, and response to, recruitment signals depend on current conditions. Using fully automatic radio-frequency
identification (RFID) technology to follow the foraging activity of tagged bumblebees (Bombus terrestris) during 16,000 foraging bouts, we tested whether the cue provided by stored food (the number of full honeypots) could modulate
the response of workers to the recruitment pheromone signal. Artificial foraging pheromones were applied to colonies with
varied levels of food reserves. The response to recruitment pheromones was stronger in colonies with low food, resulting in
more workers becoming active and more foraging bouts being performed. In addition to previous reports showing that in colonies
with low food successful foragers perform more excited runs during which they release recruitment pheromone and inactive workers
are more prone to leave the nest following nectar influx, our results indicate that evolution has shaped a third pathway that
modulates bumblebee foraging activity, thus preventing needless energy expenditure and exposure to risk when food stores are
already high. This new feedback loop is intriguing since it involves context-dependent response to a signal. It highlights
the integration of information from both forager-released pheromones (signal) and nutritional status (cue) that occurs within
individual workers before making the decision to start foraging. Our results support the emerging view that responses to pheromones
may be less hardwired than commonly acknowledged.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
305.
Thomas C. Ings Nigel E. Raine Lars Chittka 《Behavioral ecology and sociobiology》2009,63(8):1207-1218
Studies of innate colour preference and learning ability have focused on differences at the species level, rather than variation among populations of a single species. Initial strength and persistence of colour preferences are likely to affect colour choices of naïve flower visitors. We therefore study the influence of both the strength and persistence of innate colour preference (for blue) on an operant learning task (associating food reward with yellow flowers) in two populations of the bumblebee Bombus terrestris. We found that both strength and persistence of blue preference differed significantly between populations: B. terrestris dalmatinus had a weaker and less persistent blue preference than B. terrestris audax. These differences in preference also influenced learning performance. Considering only landing behaviours, one-trial learning occurred in the majority (73%) of bees, and was achieved sooner in B. terrestris dalmatinus because of its weaker blue preference. However, compared to landing behaviours the relative frequency of approach flights to rewarding and unrewarding flower types changed more slowly with task experience in both populations. When considering both approaches and landings, the rate of learning, following the first rewarded learning trial, was faster in B. terrestris audax than B. terrestris dalmatinus. However, the net effects of population differences in blue preference and learning dynamics result in similar final levels of task performance. Our results provide new evidence of behavioural differences among isolated populations within a single species, and raise intriguing questions about the ecological significance and adaptive nature of colour preference. 相似文献
306.
The strongly nucleophilic cob(I)alamin, i.e. Vitamin B12 with Co(III) reduced to Co(I), is introduced as a trapping agent in the determination of concentrations of electrophilic reagents. This compound was applied, in comparison with the previously used moderately reactive nicotinamide (H.J.C.F. Nelis and J.E. Sinsheimer (1981). Anal. Biochem., 115, 151.). Oxiranes, metabolites of 1-alkenes, were chosen as model electrophiles. The reagents (nicotinamide and cob(I)alamin) were evaluated in the determination of the rates of reaction toward valine methylamide, a model of N-terminal valines in hemoglobin often used for monitoring of doses in vivo of genotoxic carcinogens. The rate constants for reaction at 37°C with valine methylamide (k VMA) determined by the cob(I)alamin and nicotinamide procedure, respectively, were for ethylene oxide (1.6, 1.7), propylene oxide (0.9, 1.1), 1,2-epoxybutane (0.7, 0.8) and 1,2-epoxyoctane (0.5, 0.6) M?1?h?1, decreasing with increasing number of carbons of the oxirane. Concentrations of oxiranes trapped with nicotinamide are underrated in reaction mixtures containing valine methylamide due to consumption by reaction with the competing nucleophile, a disturbance that is not observed in trapping with cob(I)alamin which reacts about 105 times faster than nicotinamide. Cob(I)alamin which was demonstrated to be an efficient nucleophile for trapping of electrophiles, also in the presence of competing nucleophiles, is promising as an analytical tool in toxicological studies of reactive compounds. Furthermore, cob(I)alamin can be used to detect, measure and compare electrophilic reactivity of chemical substances, a property that is associated with genotoxic potency. 相似文献
307.
Aneta Arct Szymon M. Drobniak Edyta Podmokła Lars Gustafson Mariusz Cichoń 《Behavioral ecology and sociobiology》2013,67(11):1809-1815
Extra-pair mating constitutes a relatively common reproductive strategy in many socially monogamous bird species. This strategy may considerably improve reproductive success of males, but female benefits from extra-pair matings still remain unclear and empirical evidence is scarce. This may be because genetic benefits of extra-pair mating are not always revealed. It is possible that they are shown only in unfavourable environmental conditions and hence problems arise with detecting differences between within- and extra-pair offspring whose performance is measured under favourable conditions. In order to test this prediction, we manipulated environmental conditions by altering brood sizes of blue tits and compared phenotypic characteristics of within- and extra-pair offspring in mixed-paternity broods. We found that extra-pair young exhibited a higher response to phytohemagglutinin in comparison to within-pair young, but this was only observed among nestlings from experimentally enlarged broods. These results indicate that genetic benefits may interact with the environment, and thus benefits of extra-pair mating are likely to become visible only when conditions are relatively unfavourable. 相似文献
308.
309.
Towards a sustainable Russian forest sector 总被引:4,自引:0,他引:4
Lars Carlsson 《Natural resources forum》2000,24(1):31-37
Russia's forest resources are enormous, but despite almost ten years of transition, problems are still immense, in terms of commercial output and with respect to forest management. This article suggests that one way of changing the situation is to introduce community management of forests. Using the Swedish forest commons as an example, this article argues that such a change in property rights will provide an alternative to massive privatization of the forests and to the undesirable continuation or strengthening of state forest management. Finally, it is concluded that such an introduction of new property rights regimes will not provide the solution to the problems, but rather will contribute to the establishment of a better institutional framework in the Russian forest sector. 相似文献
310.