| 1. |
- Hansson, Bengt, et al.
(författare)
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The quality and the timing hypotheses evaluated using data on great reed warblers
- 2000
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 90:3, s. 575-581
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Tidskriftsartikel (refereegranskat)abstract
- The seasonal decline in reproductive success observed in many animal species may be caused by timing per se (timing hypothesis) or by variation in phenotypic quality between early and late breeding females (quality hypothesis). To distinguish between these two hypotheses, several studies of birds have used clutch removal experiments to manipulate breeding date. However; removal experiments also increase the females' previous reproductive effort due to the production of an extra clutch and a longer incubation period. According to life-history theory an increase in reproductive effort lowers future reproduction. Hence, life-history theory predicts lowered success of replacement broods for other reasons than expected from the timing hypothesis. Female great reed warblers, Acrocephalus ni arundinaceus, studied in Sweden are frequently exposed to nest predation, after which many lay replacement clutches. In order to examine possible effects of previous reproductive effort on different fitness components, we analysed the re-laying frequency and the reproductive success of replacement broods in relation to time of the season and previous reproductive effort (measured as the length of the previous breeding attempt, LPB). In clutches of re-laying females both the number of fledglings and the proportion of recruits were negatively correlated with LPB, whereas re-laying frequency and clutch size were not related to LPB. We expect such relationships to be present also among other species. Consequently, the use of replacement clutches, as for example in clutch removal experiments, in evaluations of the cause of the often observed seasonal decline in various fitness components, might exaggerate the importance of the timing hypothesis over the quality hypothesis.
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| 2. |
- Knape, Jonas, et al.
(författare)
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An analysis of hatching success in the great reed warbler Acrocephalus arundinaceus
- 2008
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; :117, s. 430-438
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Tidskriftsartikel (refereegranskat)abstract
- Hatching success is a potentially important fitness component for avian species. Previous studies of hatching success in natural populations have primarily focused on effects of inbreeding but a general understanding of variation in hatching success is lacking. We analyse data on hatching success in a population of great reed warblers Acrocephalus arundinaceus in Lake Kvismaren in south central Sweden. The effects of a range of covariates, including three measures of inbreeding as well as effects of classifications in the data (such as identities of individuals), on hatching success are analysed simultaneously. This is done by means of fitting Bayesian binomial mixed models using Markov chain Monte Carlo methods. Using random effects for each individual parent we check for unexplained variation in hatching success among male and female individuals and compare it to effects of covariates such as degree of inbreeding. Model selection showed that there was a significant amount of unexplained variation in hatching probability between females. This was manifested by a few females laying eggs with a substantially lower hatching success than the majority of the females. The deviations were of the same order of magnitude as the significant effect of parent relatedness on hatching success. Whereas the negative effect of parent relatedness on hatchability is an expression of inbreeding, the female individual effect is not due to inbreeding and could reflect maternal effects, that females differ in fertilisation and/or incubation ability, or an over representation of genetic components from the female acting on the early developing embryo.
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| 3. |
- Eichhorn, Götz, et al.
(författare)
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Resting metabolic rate in migratory and non-migratory geese following range expansion : go south, go low
- 2019
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 128:10, s. 1424-1434
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Tidskriftsartikel (refereegranskat)abstract
- While many species suffer from human activities, some like geese benefit and may show range expansions. In some cases geese (partially) gave up migration and started breeding at wintering and stopover grounds. Range expansion may be facilitated and accompanied by physiological changes, especially when associated with changes in migratory behaviour. Interspecific comparisons found that migratory tendency is associated with a higher basal or resting metabolic rate (RMR). We compared RMR of individuals belonging to a migratory and a sedentary colony of barnacle geese Branta leucopsis. The migratory colony is situated in the traditional arctic breeding grounds (Russia), whereas the sedentary colony has recently been established in the now shared wintering area (the Netherlands). We measured RMR by oxygen consumption (Vo2) during two ontogenetic phases (juvenile growth and adult wing moult). We also investigated juvenile growth rates and adult body mass dynamics. Mass-independent Vo2 was 13.6% lower in goslings from the sedentary colony than in goslings from the migratory colony. Similarly, in adult geese, mass-independent Vo2 was 15.5% lower in sedentary than in migratory conspecifics. Goslings in the Netherlands grew 36.2% slower than goslings in Russia, while we found no differences in body dimensions in adults. Adult geese from both colonies commenced wing moult with similar body stores, but whereas Russian barnacle geese maintained this level throughout moult, body stores in geese from the Netherlands fell, being 8.5% lower half-way through the moult. We propose that the colony differences in resting metabolic rate, growth rate and body mass dynamics during moult can be explained by environmental and behavioural differences. The less stringent time constraints combined with poorer foraging opportunities allow for a smaller ‘metabolic machinery’ in non-migratory geese. Our analysis suggests that range expansion may be associated with changes in physiology, especially when paired with changes in migratory tendency.
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| 4. |
- Ellis, Vincenzo A., et al.
(författare)
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Explaining prevalence, diversity and host specificity in a community of avian haemosporidian parasites
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:9, s. 1314-1329
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Tidskriftsartikel (refereegranskat)abstract
- Many hypotheses attempt to explain parasite–host associations, but rarely are they examined together in a single community. For hosts, key traits are the proportion of infected individuals (prevalence) and the diversity of parasites infecting them. A key parasite trait is host specificity, ranging from specialists infecting one or a few closely related species to generalists infecting many species. We tested 10 hypotheses to explain host-parasite associations; five ‘host-centric’ (e.g. prevalence is related to host abundance) and five ‘parasite-centric’ (e.g. parasite abundance is related to host specificity). We analyzed a community of 67 locally transmitted avian haemosporidian parasite lineages (genera Plasmodium, Haemoproteus or Leucocytozoon), sampled from 2726 birds (64 species) in southern Sweden. Among host-centric hypotheses, Haemoproteus and Leucocytozoon prevalence and Haemoproteus diversity were related to host habitat preferences, whereas there were no relationships with host abundance or body mass. Haemoproteus and Leucocytozoon prevalences were more similar among closely related than among distantly related host species. Haemoproteus prevalence and diversity were lower in host species with few close relatives (‘evolutionarily distinct’ hosts). Among parasite-centric hypotheses, most lineages, even relative generalists, infected closely related host species more often than expected by chance. However, the host species of Haemoproteus and Leucocytozoon lineages overlapped less among lineages than expected by chance. Specialists did not reach higher prevalences than generalists on single host species. However, the abundance of Haemoproteus lineages was related to host specificity with generalists more common than specialists; this was driven by three closely related generalists. Host specificity of parasites was unrelated to the abundance or evolutionarily distinctiveness of their hosts. Parasite communities are likely structured by many factors and cannot be explained by hypotheses focusing solely on hosts or parasites. However, we found consistent effects of host phylogenetic relationships, plausibly a result of evolutionarily conserved host immune systems limiting parasite distributions.
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| 5. |
- Nord, Andreas, et al.
(författare)
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A trade-off between perceived predation risk and energy conservation revealed by an immune challenge experiment
- 2014
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 123:9, s. 1091-1100
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Tidskriftsartikel (refereegranskat)abstract
- Energy is typically a limiting factor for animals during boreal zone winters, when low temperatures increase the cost of thermoregulation at the same times as short day-lengths and snow cover constrain foraging opportunities. Under these circumstances animals use a suite of behavioural and physiological adaptations to avoid overnight starvation. However, it is poorly understood how such strategies are affected by increased energy demands from other physiological systems. Thus, we used free-ranging blue tits (Cyanistes caeruleus L.) to test if competing demands for energy (here induced by a non-inflammatory, antibody-mediated immune challenge) would affect nocturnal body temperature (a predictor of energy expenditure in small animals) and energy-saving nest box roosting behaviour. We also assessed if the immune challenge incurred long-term survival costs. We found no evidence that body temperature regulation differed between immune-challenged and saline-injected birds. Nor did the immune challenge reduce survival to the next breeding season. However, old (second winter or older) immune-challenged birds continued roosting in nest boxes to a larger extent at the peak immune response, despite increased perceived predation risk induced by the preceding capture and immunization. In contrast, old control birds were less prone to roost in nest boxes after capture and saline injection. This difference was less pronounced in young (first winter) birds. We interpret the increased risk-taking behaviour in immune-challenged birds as a consequence of a higher need for exploiting the thermal benefits of nest box roosting to reduce energy loss. This suggests that resource deficiency might be a stronger predictor of overnight survival than the threat of nocturnal predation in this system. As such, our study provides insights into the classic trade-off between starvation and predation risk, in suggesting that priority is given to minimizing the risk of starvation in situations where both starvation and predation risks increase during cold winter nights.
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