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| 2. |
- Dahl, Jonas, et al.
(författare)
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Against the flow: chemical detection of downstream predators in running waters
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1403, s. 1339-1344
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Tidskriftsartikel (refereegranskat)abstract
- In running waters, chemical cues have generally been assumed to always come from upstream locations. Here, we present ¢eld and laboratory evidence that Gammarus pulex can use chemical cues from down- stream predators to adaptively adjust drifting behaviour. In the ¢eld, signi¢cantly fewer Gammarus migrated into stream enclosures where brown trout (Salmo trutta) were present than into control enclo- sures. In a subsequent laboratory experiment, Gammarus actively avoided live trout and trout chemicals placed downstream in an arti¢cial stream, whereas no e¡ects were found in response to control or visual cues.We suggest that the mechanism explaining the ability of Gammarus to detect downstream predators is use of back£ows, which locally transport ¢sh chemicals against the main £ow. Such back£ows are both created by the Gammarus itself and by surrounding substrate heterogeneity. These results profoundly a¡ect the way in which we view the chemical environment of running waters and have important implications for empirical and theoretical work evaluating predator e¡ects in running waters, as they demonstrate that prey immigration rates can depend on downstream predator densities.
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| 4. |
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| 5. |
- Hansson, Lars-Anders, et al.
(författare)
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Consumption patterns, complexity and enrichment in aquatic food chains
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
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| 6. |
- Hardling, R., et al.
(författare)
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Experimental evidence for low intra-pair cache pilfering rates in European nuthatches
- 1995
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452. ; 260:1358, s. 127-130
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Tidskriftsartikel (refereegranskat)abstract
- European nuthatches, Sitta europaea, live all year in permanent pair-territories. In winter, hoarded food is an important food source. To measure the rate of cache pilfering within pairs, each member of six pairs was supplied with either white- or dark-shelled sunflower seeds which the birds cached. When each bird had cached some 100-300 seeds, the feeder was removed and the birds were monitored during their normal foraging. For each sunflower seed that the nuthatches retrieved, the colour of the seed and the sex of the retrieving bird were recorded. In all pairs, each member almost exclusively retrieved seeds of the colour it had itself cached, pilfering amounting to less than 5%. As no clear differences in hoarding niches were detected between the sexes, these results suggest that caches were relocated with the aid of memory.
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| 7. |
- Hemborg, Christer, et al.
(författare)
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A sexual conflict in collared flycatchers, Ficedula albicollis : early male moult reduces female fitness
- 1998
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 265:1409, s. 2003-2007
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Tidskriftsartikel (refereegranskat)abstract
- A sexual conflict over levels of parental care occurs in most animals with biparental care, and studies of sexual differences in levels of parental care have usually focused on its intra-annual fitness consequences. We investigated inter-annual fitness consequences of a sexual difference in timing of feather replacement (moult) in collared flycatchers (Ficedula albicollis). In this study, males overlapped reproduction and moult more often than females, they also initiated their moult at an earlier stage of breeding than females. Females mated to males with a moult-breeding overlap had significantly lowered survival chances than females mated with males initiating moult after breeding. Furthermore, females mated with moulting males risked a lowered future fecundity in terms of a delayed start to breeding in the following season. However, early moulting males achieved a similar reproductive success as males initiating moult after breeding. Likewise, male survival probability to the following breeding season did not differ between early and late moulting individuals, nor was there any evidence that males gained or lost in future mating advantages by moulting early. These results show not only that a sexual conflict over timing of moult may operate, but also that it can impose severe fitness consequences, in terms of reduced future fecundity and survival probability, upon the 'losing' sex.
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| 8. |
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| 9. |
- Härlin, Mikael
(författare)
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Phylogenetic approaches to nomenclature : a comparison based on a nemertean case study.
- 1999
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 266:1434, s. 2201-2207
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Tidskriftsartikel (refereegranskat)abstract
- Phylogenetic approaches to biological nomenclature are becoming increasingly common. Here I compare the behaviour of two such approaches, the phylogenetic system of definition and the phylogenetic system of reference, when there is a shift in the preference of phylogenetic hypotheses. The comparison is based on a case study from nemertean systematics and is the first to compare two different phylogenetic approaches throughout three stages of change, including two stages of phylogenetic nomenclature. It is concluded that a phylogenetic system of reference in combination with uninomials is superior in conveying phylogenetic information.
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| 10. |
- Keynes, RD, et al.
(författare)
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Modelling the activation, opening, inactivation and reopening of the voltage-gated sodium channel
- 1998
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society. - 0962-8452 .- 1471-2954. ; 265:1393, s. 263-270
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Tidskriftsartikel (refereegranskat)abstract
- A model of the voltage-gated sodium channel is put forward suggesting that the four S4 voltage-sensors behave as screw-helices making a series of discrete transitions that carry one elementary charge for each notch of the screw helix. After the channel has been activated by the first two steps R reversible arrow P reversible arrow A in all four domains, followed by a voltage-independent rearrangement, it is opened by a third cooperative step A reversible arrow B in domains I, II and III in conjunction with hydration. Inactivation is a voltage-dependent process controlled by the third step A reversible arrow I in sensor IVS4, and the closing of the channel is brought about its dehydration. From the inactivated steady state the channel may be reopened by a fourth step, I reversible arrow C in sensor IVS4 and rehydration. The computed kinetics of the model are shown to conform closely with those observed experimentally.
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