| 1. |
- Hansson, Bengt, et al.
(författare)
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Heritability of dispersal in the great reed warbler
- 2003
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 6:4, s. 290-294
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Tidskriftsartikel (refereegranskat)abstract
- Dispersal is commonly considered to be a condition-dependent behaviour with no or low heritability. Here, we show that dispersal in the great reed warbler (Acrocephalus arundinaceus ) has a high heritability. Analyses of capture-recapture data of male great reed warblers gathered from the species' whole Swedish breeding range revealed a remarkable offspring-parent resemblance in dispersal behaviour (philopatry vs. inter-population dispersal). Also, the degree of dispersal differed between cohorts, which shows that dispersal was partly conditionally dependent. The offspring to mid-parent estimate of heritability was 0.50. In a previous study of the same data set of male offspring, we did not detect associations between dispersal and several relevant environmental, parental and offspring condition factors. Thus, our results indicate that variation in dispersal partly has a genetic basis in great reed warblers.
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| 2. |
- Lundberg, Per, et al.
(författare)
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Species loss leads to community closure
- 2000
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 3:6, s. 465-468
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Tidskriftsartikel (refereegranskat)abstract
- Global extinction of a species is sadly irreversible. At a local scale, however, extinctions may be followed by re-invasion. We here show that this is not necessarily the case and that an ecological community may close its doors for re-invasion of species lost from it. Previous studies of how communities are assembled have shown that there may be rules for that process and that limitations are set to the order by which species are introduced and put together. Instead of focusing on the assembly process we randomly generated simple competitive model communities that were stable and allowed for two to 10 coexisting species. When a randomly selected single species was removed from the community, the cascading species loss was recorded and frequently the resulting community was more than halved. Cascading extinctions have previously been recorded, but we here show that the relative magnitude of the cascade is dependent on community size land not only trophic structure) and that the reintroduction of the original species lost often is impossible. Hence, species loss does not simply leave a void potentially refilled, bur: permanently alters the entire community structure and consequently the adaptive landscape for potential re-invaders.
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| 3. |
- Råberg, Lars, et al.
(författare)
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The cost of an immune response: vaccination reduces parental effort
- 2000
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 3:5, s. 382-386
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental assumption of theories of the ecology and evolution of inducible defences is that protective responses to attacks by parasites or predators should not only have benefits, but also costs. The vertebrate immune system is by far the best studied example of an inducible defence, yet little is known about the costs of an immune response, especially in natural populations. To test: if an immune response per se is costly, we induced an antibody response in female blue tits, Parus caeruleus, by immunising them with human diphtheria-tetanus vaccine, and compared their nestling-feeding rate with that of saline-injected controls. We found that vaccinated females reduced their nestling feeding rate, thus demonstrating a cost of the immune response in the currency of parental effort.
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| 4. |
- Williams, C K, et al.
(författare)
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The collapse of cycles in the dynamics of North American grouse populations
- 2004
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 7:12, s. 1135-1142
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic dynamics of bird and mammal populations are commonly reported in northern latitudes throughout the world, and recent European observations on rodents and grouse suggest that cycle periods decline towards southern latitudes. To investigate latitudinal patterns of cyclic dynamics in North America, we assembled 27 long-term data sets collected between 1939 and 2001 for three grouse species. By fitting the data with autoregressive models to measure direct and delayed density dependence, we show that, in contrast to European studies, North American grouse exhibit period increases from north to south, with cycles collapsing via period lengthening. This occurs because delayed density dependence decreases in southern latitudes, whereas direct density dependence increases. These results show that cyclic dynamics can dissipate by period lengthening as well as the period shortening postulated for European grouse and rodents.
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| 5. |
- Wilson, W G, et al.
(författare)
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Biodiversity and species interactions: extending Lotka-Volterra community theory
- 2003
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 6:10, s. 944-952
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Tidskriftsartikel (refereegranskat)abstract
- A new analysis of the nearly century-old Lotka-Volterra theory allows us to link species interactions to biodiversity patterns, including: species abundance distributions, estimates of total community size, patterns of community invasibility, and predicted responses to disturbance. Based on a few restrictive assumptions about species interactions, our calculations require only that the community is sufficiently large to allow a mean-field approximation. We develop this analysis to show how an initial assemblage of species with varying interaction strengths is predicted to sort out into the final community based on the species' predicted target densities. The sorting process yields predictions of covarying patterns of species abundance, community size, and species interaction strengths. These predictions can be tested using enrichment experiments, examination of latitudinal and productivity gradients, and features of community assembly.
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| 6. |
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| 7. |
- Borrvall, Charlotte, et al.
(författare)
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Biodiversity lessens the risk of cascading extinction in model food webs
- 2000
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 3:2, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- Due to the complex interactions between species in food webs, the extinction of one species could lead to a cascade of further extinctions and hence cause dramatic changes in species composition and ecosystem processes. We found that the risk of additional species extinction, following the loss of one species in model food webs, decreases with the number of species per functional group. For a given number of species per functional group, the risk of further extinctions is highest when an autotroph is removed and lowest when a top predator is removed. In addition, stability decreases when the distribution of interaction strengths in the webs is changed from equal to skew (few strong and many weak links). We also found that omnivory appears to stabilize model food webs. Our results indicate that high biodiversity may serve as an insurance against radical ecosystem changes.
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| 8. |
- McNamara, J. M., et al.
(författare)
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Measurement error and estimates of population extinction risk
- 2004
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 7:1, s. 16-20
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Tidskriftsartikel (refereegranskat)abstract
- It is common to estimate the extinction probability for a vulnerable population using methods that are based on the mean and variance of the long-term population growth rate. The numerical values of these two parameters are estimated from time series of population censuses. However, the proportion of a population that is registered at each census is typically not constant but will vary among years because of stochastic factors such as weather conditions at the time of sampling. Here, we analyse how such sampling errors influence estimates of extinction risk and find sampling errors to produce two opposite effects. Measurement errors lead to an exaggerated overall variance, but also introduce negative autocorrelations in the time series (which means that estimates of annual growth rates tend to alternate in size). If time series data are treated properly these two effects exactly counter balance. We advocate routinely incorporating a measure of among year correlations in estimating population extinction risk.
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| 9. |
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| 10. |
- Olsson, Mats, 1960, et al.
(författare)
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Haldane rules: costs of outbreeding at production of daughters in sand lizards
- 2004
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 7:10, s. 924-928
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Tidskriftsartikel (refereegranskat)abstract
- Haldane's rule is one of the most widely applicable paradigms in evolutionary biology, stating that in species crossings, the heterogametic sex will suffer more severely in terms of sterility and inviability. We address this in a within-species outbreeding situation by assessing the risk of producing inviable offspring depending on the sex ratio of the clutch produced in between-population crossings in the laboratory. In crossings between male and female sand lizards (Lacerta agilis) from two different sampling regions, one in Sweden, one in central Europe, risk of gametic incompatibility is unaffected by outbreeding, but offspring from between-population crossings show 300% higher malformation frequency and 10% lower hatching success. The risk of having inviable offspring increases with the production of daughters, i.e. the hemizygous sex in this species (ZW). Such sex-specific genetic costs of offspring production need to be incorporated into life history ecology, e.g. sex allocation theory.
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