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  • 1
    Online Resource
    Online Resource
    Wiley ; 2013
    In:  Aging Cell Vol. 12, No. 2 ( 2013-04), p. 330-332
    In: Aging Cell, Wiley, Vol. 12, No. 2 ( 2013-04), p. 330-332
    Type of Medium: Online Resource
    ISSN: 1474-9718
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2013
    detail.hit.zdb_id: 2099130-7
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2016
    In:  Behavioral Ecology Vol. 27, No. 4 ( 2016), p. 1087-1096
    In: Behavioral Ecology, Oxford University Press (OUP), Vol. 27, No. 4 ( 2016), p. 1087-1096
    Type of Medium: Online Resource
    ISSN: 1045-2249 , 1465-7279
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2016
    detail.hit.zdb_id: 1496189-1
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Wiley ; 2023
    In:  Journal of Avian Biology Vol. 2023, No. 5-6 ( 2023-05)
    In: Journal of Avian Biology, Wiley, Vol. 2023, No. 5-6 ( 2023-05)
    Abstract: Variation in developmental conditions is known to affect fitness in later life, but the mechanisms underlying this relationship remain elusive. We previously found in jackdaws Corvus monedula that larger eggs resulted in larger nestlings up to fledging. Through a cross‐foster experiment of complete clutches we tested whether this association can be attributed to egg size per se, or to more proficient parents producing larger eggs and larger nestlings, with the latter effect being more or less independent of egg size. Due to other manipulations post‐hatching, we primarily investigated effects on nestling mass on day 5, which we show to predict survival until fledging. We introduce a new statistical approach to compare the competing hypotheses and discuss the multiple advantages of this approach over current practice of which we report the results for comparison. We conclude that 92% of the slope of the association between egg size and nestling mass can be attributed to a direct effect of egg size. The remaining 8% of the slope can be attributed to aspects of parental chick rearing ability as reflected in egg size, but this component did not deviate significantly from zero. Intriguingly, the effect of egg size on day 5 nestling mass was steeper (1.7 g cm −3 ) than the effect of egg size on day 1 hatchling mass (0.7 g cm −3 ). Early growth is exponential, and the difference in effect size may therefore be explained by hatchlings from large eggs being further in their development at hatching. The direct effect of egg size on nestling mass raises the question what causes egg size variation in jackdaws.
    Type of Medium: Online Resource
    ISSN: 0908-8857 , 1600-048X
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2028018-X
    SSG: 12
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  • 4
    In: Journal of Animal Ecology, Wiley, Vol. 89, No. 6 ( 2020-06), p. 1395-1407
    Abstract: The assumption that reproductive effort decreases somatic state, accelerating ageing, is central to our understanding of life‐history variation. Maximal reproductive effort early in life is predicted to be maladaptive by accelerating ageing disproportionally, decreasing fitness. Optimality theory predicts that reproductive effort is restrained early in life to balance the fitness contribution of reproduction against the survival cost induced by the reproductive effort. When adaptive, the level of reproductive restraint is predicted to be inversely linked to the remaining life expectancy, potentially resulting in a terminal effort in the last period of reproduction. Experimental tests of the reproductive restraint hypothesis require manipulation of somatic state and subsequent investigation of reproductive effort and residual life span. To our knowledge the available evidence remains inconclusive, and hence reproductive restraint remains to be demonstrated. We modulated somatic state through a lifelong brood size manipulation in wild jackdaws and measured its consequences for age‐dependent mortality and reproductive success. The assumption that lifelong increased brood size reduced somatic state was supported: Birds rearing enlarged broods showed subsequent increased rate of actuarial senescence, resulting in reduced residual life span. The treatment induced a reproductive response in later seasons: Egg volume and nestling survival were higher in subsequent seasons in the increased versus reduced broods' treatment group. We detected these increases in egg volume and nestling survival despite the expectation that in the absence of a change in reproductive effort, the reduced somatic state indicated by the increased mortality rate would result in lower reproductive output. This leads us to conclude that the higher reproductive success we observed was the result of higher reproductive effort. Our findings show that reproductive effort negatively covaries with remaining life expectancy, supporting optimality theory and confirming reproductive restraint as a key factor underpinning life‐history variation.
    Type of Medium: Online Resource
    ISSN: 0021-8790 , 1365-2656
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2006616-8
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2022
    In:  Molecular Ecology Vol. 31, No. 23 ( 2022-12), p. 6308-6323
    In: Molecular Ecology, Wiley, Vol. 31, No. 23 ( 2022-12), p. 6308-6323
    Abstract: Telomere length and telomere shortening predict survival in many organisms. This raises the question of the contribution of genetic and environmental effects to variation in these traits, which is still poorly known, particularly for telomere shortening. We used experimental (cross‐fostering) and statistical (quantitative genetic “animal models”) means to disentangle and estimate genetic and environmental contributions to telomere length variation in pedigreed free‐living jackdaws ( Corvus monedula ). Telomere length was measured twice in nestlings, at ages 4 ( n  = 715) and 29 days ( n  = 474), using telomere restriction fragment (TRF) analysis, adapted to exclude interstitial telomeric sequences. Telomere length shortened significantly over the nestling period (10.4 ± 0.3 bp day –1 ) and was highly phenotypically ( r P  = 0.95 ± 0.01) and genetically ( r G   〉  0.99 ± 0.01) correlated within individuals. Additive genetic effects explained a major part of telomere length variation among individuals, with its heritability estimated at h 2  = 0.74 on average. We note that TRF‐based studies reported higher heritabilities than qPCR‐based studies, and we discuss possible explanations. Parent–offspring regressions yielded similar heritability estimates for mothers and fathers when accounting for changes in paternal telomere length over life. Year effects explained a small but significant part of telomere length variation. Heritable variation for telomere shortening was low ( h 2  = 0.09 ± 0.11). The difference in heritability between telomere length (high) and telomere shortening (low) agrees with evolutionary theory, in that telomere shortening has stronger fitness consequences in this population. Despite the high heritability of telomere length, its evolvability, which scales the additive genetic variance by mean telomere length, was on average 0.48%. Hence, evolutionary change of telomere length due to selection is likely to be slow.
    Type of Medium: Online Resource
    ISSN: 0962-1083 , 1365-294X
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2020749-9
    detail.hit.zdb_id: 1126687-9
    SSG: 12
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  • 6
    In: Journal of Evolutionary Biology, Wiley, Vol. 34, No. 10 ( 2021-10), p. 1624-1636
    Abstract: Understanding how species can thrive in a range of environments is a central challenge for evolutionary ecology. There is strong evidence for local adaptation along large‐scale ecological clines in insects. However, potential adaptation among neighbouring populations differing in their environment has been studied much less. We used RAD sequencing to quantify genetic divergence and clustering of ten populations of the field cricket Gryllus campestris in the Cantabrian Mountains of northern Spain, and an outgroup on the inland plain. Our populations were chosen to represent replicate high and low altitude habitats. We identified genetic clusters that include both high and low altitude populations indicating that the two habitat types do not hold ancestrally distinct lineages. Using common‐garden rearing experiments to remove environmental effects, we found evidence for differences between high and low altitude populations in physiological and life‐history traits. As predicted by the local adaptation hypothesis, crickets with parents from cooler (high altitude) populations recovered from periods of extreme cooling more rapidly than those with parents from warmer (low altitude) populations. Growth rates also differed between offspring from high and low altitude populations. However, contrary to our prediction that crickets from high altitudes would grow faster, the most striking difference was that at high temperatures, growth was fastest in individuals from low altitudes. Our findings reveal that populations a few tens of kilometres apart have independently evolved adaptations to their environment. This suggests that local adaptation in a range of traits may be commonplace even in mobile invertebrates at scales of a small fraction of species' distributions.
    Type of Medium: Online Resource
    ISSN: 1010-061X , 1420-9101
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 92624-3
    detail.hit.zdb_id: 1465318-7
    SSG: 12
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  • 7
    In: Ecology Letters, Wiley, Vol. 18, No. 3 ( 2015-03), p. 315-315
    Type of Medium: Online Resource
    ISSN: 1461-023X , 1461-0248
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2020195-3
    SSG: 12
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  • 8
    In: Functional Ecology, Wiley, Vol. 31, No. 3 ( 2017-03), p. 719-727
    Abstract: Biomarkers that predict fitness are instrumental in unravelling mechanisms that link environmental conditions to fitness. However, development is likely to be better canalized for traits with stronger fitness effects. As a consequence, traits that are sensitive to developmental conditions may be poor fitness predictors and vice versa, and we tested for such effects using feather fault bars (translucent areas on feathers associated with developmental stress) in nestling birds. We manipulated developmental conditions (brood size) in free‐living jackdaws ( Coloeus monedula ) and compared the effect on fault bar number between two feather types, tail and wing coverts. Fault bar number in the two feather types correlated poorly, indicating they can be considered different traits. Subsequently, we monitored local survival to investigate how well both traits linked developmental conditions to survival prospects. Tail fault bar number reflected developmental conditions better than the number of fault bars in the wings: when pre‐manipulation brood size was small, nestlings had more tail fault bars when brood size was subsequently enlarged, while there was no such manipulation effect on the number of fault bars in wing coverts. In contrast, fault bar number in wing coverts better predicted fledgling local survival compared to tail coverts. We conclude that fault bar number in tail coverts is a biomarker of developmental conditions, while fault bar number in wing coverts is a predictor of survival prospects, but neither trait successfully links developmental conditions to fitness prospects. These findings are in agreement with the expectation that development of traits with a stronger relation to fitness will be better canalized. We discuss three hypotheses that can explain why despite canalization there are traits that are both sensitive to developmental conditions and predict fitness prospects. A lay summary is available for this article.
    Type of Medium: Online Resource
    ISSN: 0269-8463 , 1365-2435
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2020307-X
    detail.hit.zdb_id: 619313-4
    SSG: 12
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  • 9
    In: Ecology Letters, Wiley, Vol. 17, No. 5 ( 2014-05), p. 599-605
    Abstract: Optimality theories of ageing predict that the balance between reproductive effort and somatic maintenance determines the rate of ageing. Laboratory studies find that increased reproductive effort shortens lifespan, but through increased short‐term mortality rather than ageing. In contrast, high fecundity in early life is associated with accelerated senescence in free‐living vertebrates, but these studies are non‐experimental. We performed lifelong brood size manipulation in free‐living jackdaws. Actuarial senescence – the increase in mortality rate with age – was threefold higher in birds rearing enlarged‐ compared to reduced broods, confirming a key prediction of the optimality theory of ageing. Our findings contrast with the results of single‐year brood size manipulation studies carried out in many species, in which there was no overall discernible manipulation effect on mortality. We suggest that our and previous findings are in agreement with predictions based on the reliability theory of ageing and propose further tests of this proposition.
    Type of Medium: Online Resource
    ISSN: 1461-023X , 1461-0248
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 2020195-3
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    The Royal Society ; 2014
    In:  Proceedings of the Royal Society B: Biological Sciences Vol. 281, No. 1791 ( 2014-09-22), p. 20141045-
    In: Proceedings of the Royal Society B: Biological Sciences, The Royal Society, Vol. 281, No. 1791 ( 2014-09-22), p. 20141045-
    Abstract: Behaviour may contribute to changes in fitness prospects with age, for example through effects of age-dependent social dominance on resource access. Older individuals often have higher dominance rank, which may reflect a longer lifespan of dominants and/or an increase in social dominance with age. In the latter case, increasing dominance could mitigate physiological senescence. We studied the social careers of free-living jackdaws over a 12 year period, and found that: (i) larger males attained higher ranks, (ii) social rank increased with age within individuals, and (iii) high-ranked individuals had shorter lifespan suggesting that maintaining or achieving high rank and associated benefits comes at a cost. Lastly, (iv) social rank declined substantially in the last year an individual was observed in the colony, and through its effect on resource access this may accelerate senescence. We suggest that behaviour affecting the ability to secure resources is integral to the senescence process via resource effects on somatic state, where behaviour may include not only social dominance, but also learning, memory, perception and (sexual) signalling. Studying behavioural effects on senescence via somatic state may be most effective in the wild, where there is competition for resources, which is usually avoided in laboratory conditions.
    Type of Medium: Online Resource
    ISSN: 0962-8452 , 1471-2954
    Language: English
    Publisher: The Royal Society
    Publication Date: 2014
    detail.hit.zdb_id: 1460975-7
    SSG: 12
    SSG: 25
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