Predictions about the fate of species or populations under climate change scenarios typically neglect adaptive evolution and phenotypic plasticity, the two major mechanisms by which organisms can ...adapt to changing local conditions. As a consequence, we have little understanding of the scope for organisms to track changing environments by in situ adaptation. Here, we use a detailed individual-specific long-term population study of great tits (Parus major) breeding in Wytham Woods, Oxford, UK to parameterise a mechanistic model and thus directly estimate the rate of environmental change to which in situ adaptation is possible. Using the effect of changes in early spring temperature on temporal synchrony between birds and a critical food resource, we focus in particular on the contribution of phenotypic plasticity to population persistence. Despite using conservative estimates for evolutionary and reproductive potential, our results suggest little risk of population extinction under projected local temperature change; however, this conclusion relies heavily on the extent to which phenotypic plasticity tracks the changing environment. Extrapolating the model to a broad range of life histories in birds suggests that the importance of phenotypic plasticity for adjustment to projected rates of temperature change increases with slower life histories, owing to lower evolutionary potential. Understanding the determinants and constraints on phenotypic plasticity in natural populations is thus crucial for characterising the risks that rapidly changing environments pose for the persistence of such populations.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Personality and metabolic rate are predicted to show covariance on methodological and functional grounds, but empirical studies at the individual level are rare, especially in natural populations. ...Here we assess the relationship between exploration behaviour, an important axis of personality, and basal metabolic rate (BMR) for 680 free-living great tits Parus major, studied over three years. We find that exploration behaviour is weakly negatively related to BMR among female, but not male, birds. Moreover, we find exploration behaviour to be independent of methodological aspects of BMR measurements (e.g. activity levels, time to acclimatize) which have been suggested to be indicative of personality-related activity or stress levels during measurement. This suggests that the weak link between exploration behaviour and BMR found here is functional rather than methodological. We therefore test the hypothesis that selection favours covariance between exploration behaviour and metabolic rate, but find no evidence for correlational survival or fecundity selection. Our data therefore provide at best only very weak evidence for a functional link between personality and metabolic rate, and we suggest that studies of personality and metabolic strategies, or personality and daily energy expenditure, are required to further resolve the link between personality and metabolic rate.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
While life‐history theory predicts a tradeoff between reproduction and survival, positive covariance, indicative of heterogeneity in individual quality, is often reported among individuals from ...natural populations. We review longitudinal studies of wild bird populations that test the relationship between annual reproductive success and lifespan and find the majority to report a positive correlation, while none reports a negative correlation. Heterogeneity in individual quality in resource acquisition, masking resource‐based tradeoffs, therefore appears to be common in birds. Considering that there is little evidence for heritable variation in fitness, heterogeneity in individual quality among adults may be due to life‐long effects of developmental conditions. In a 20‐year case study on common terns Sterna hirundo, we test for life‐long effects of cohort quality and within‐cohort nest quality, but find no significant effects on long‐term proxies of quality. Since other studies do find strong life‐long effects of developmental conditions, we suggest that the brood reduction strategy adopted by common terns, causing the majority of offspring to die rapidly after hatching, efficiently reduces variation in offspring quality at independence. As such, a brood reduction strategy may contribute to reduced heterogeneity in adult survival in stochastic environments, both suggested to be more common and adaptive in long‐lived species. Further study is required to assess heterogeneity in individual reproduction, especially in relation to environmental stochasticity and species’ life‐history strategies, in order to assess whether the relative strength of selection in early and late life may indeed affect the magnitude of heterogeneity in individual quality over life, and how this is mediated by parent–offspring conflict.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
1. Population dynamics and foraging ecology are two fields of the population ecology that are generally studied separately. Yet, foraging determines allocation processes and therefore demography. ...Studies on wandering albatrosses Diomedea exulans over the past 50 years have contributed to better understand the links between population dynamics and foraging ecology. This article reviews how these two facets of population ecology have been combined to better understand ecological processes, but also have contributed fundamentally for the conservation of this long-lived threatened species. 2. Wandering albatross research has combined a 50-year long-term study of marked individuals with two decades of tracking studies that have been initiated on this species, favoured by its large size and tameness. 3. At all stages of their life history, the body mass of individuals plays a central role in allocation processes, in particular in influencing adult and juvenile survival, decisions to recruit into the population or to invest into provisioning the offspring or into maintenance. 4. Strong age-related variations in demographic parameters are observed and are linked to age-related differences in foraging distribution and efficiency. Marked sex-specific differences in foraging distribution, foraging efficiency and changes in mass over lifetime are directly related to the strong sex-specific investment in breeding and survival trajectories of the two sexes, with body mass playing a pivotal role especially in males. 5. Long-term study has allowed determining the sex-specific and age-specific demographic causes of population decline, and the tracking studies have been able to derive where and how these impacts occur, in particular the role of long-line fisheries.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Understanding the evolution of migration requires knowledge of the patterns, sources, and consequences of variation in migratory behaviour, a need exacerbated by the fact that many migratory species ...show rapid population declines and require knowledge-based conservation measures. We therefore need detailed knowledge on the spatial and temporal distribution of individuals across their annual cycle, and quantify how the spatial and temporal components of migratory behaviour vary within and among individuals.
We tracked 138 migratory journeys undertaken by 64 adult common terns (Sterna hirundo) from a breeding colony in northwest Germany to identify the annual spatiotemporal distribution of these birds and to evaluate the individual repeatability of eleven traits describing their migratory behaviour.
Birds left the breeding colony early September, then moved south along the East Atlantic Flyway. Wintering areas were reached mid-September and located at the west and south coasts of West Africa as well as the coasts of Namibia and South Africa. Birds left their wintering areas late March and reached the breeding colony mid-April. The timing, total duration and total distance of migration, as well as the location of individual wintering areas, were moderately to highly repeatable within individuals (repeatability indexes: 0.36-0.75, 0.65-0.66, 0.93-0.94, and 0.98-1.00, respectively), and repeatability estimates were not strongly affected by population-level inter-annual variation in migratory behaviour.
We found large between-individual variation in common tern annual spatiotemporal distribution and strong individual repeatability of several aspects of their migratory behaviour.
Mergibacter septicus (M. septicus), previously known as Bisgaard Taxon 40, is a recently described species within the Pasteurellaceae family. In this study, we present a M. septicus strain isolated ...from a common tern (Sterna hirundo) chick that died just after fledging from the Banter See in Wilhelmshaven, Germany. The recovered M. septicus strain underwent microbiological phenotypic characterization, followed by whole genome sequencing on Illumina and Nanopore platforms. Phenotypically, M. septicus 19Y0039 demonstrated resistance to colistin, cephalexin, clindamycin, oxacillin, and penicillin G. The genome analysis revealed a circular 1.8 Mbp chromosome without any extrachromosomal elements, containing 1690 coding DNA sequences. The majority of these coding genes were associated with translation, ribosomal structure and biogenesis, followed by RNA processing and modification, and transcription. Genetic analyses revealed that the German M. septicus strain 19Y0039 is related to the American strain M. septicus A25201T. Through BLAST alignment, twelve putative virulence genes previously identified in the M. septicus type strain A25201T were also found in the German strain. Additionally, 84 putative virulence genes distributed across nine categories, including immune modulation, effector delivery system, nutrition/metabolic factors, regulation, stress survival, adherence, biofilm, exotoxin, and motility, were also identified.
Senescence, an age-related decline in survival and/or reproductive performance, occurs in species across the tree of life. Molecular mechanisms underlying this within-individual phenomenon are still ...largely unknown, but DNA methylation changes with age are among the candidates. Using a longitudinal approach, we investigated age-specific changes in autosomal methylation of common terns, relatively long-lived migratory seabirds known to show senescence. We collected blood at 1-, 3- and/or 4-year intervals, extracted DNA from the erythrocytes and estimated autosomal DNA methylation by mapping Reduced Representative Bisulfite Sequencing reads to a
de novo
assembled reference genome. We found autosomal methylation levels to decrease with age within females, but not males, and no evidence for selective (dis)appearance of birds of either sex in relation to their methylation level. Moreover, although we found positions in the genome to consistently vary in their methylation levels, individuals did not show such strong consistent variance. These results pave the way for studies at the level of genome features or specific positions, which should elucidate the functional consequences of the patterns observed, and how they translate to the ageing phenotype.
In Focus: Weimerskirch, H. (2018). Linking demographic processes and foraging ecology in wandering albatross—Conservation implications. Journal of Animal Ecology, 87, 945–955. ...https://doi.org/10.1111/1365-2656.12817
Long‐term individual‐based studies are extremely valuable resources to study how life histories are shaped by selection on between‐individual variation in the acquisition and allocation of resources. In this issue, Weimerskirch (2018) synthesises a 50‐year study, uniquely including 20 years of individual‐based movement tracking, of the majestic wandering albatross. The synthesis shows how variation in foraging distribution and efficiency in relation to sex and age is reflected in physiology, fitness and population dynamics, and how understanding of such patterns and processes can aid conservation efforts. It thereby exemplifies why long‐term individual‐based studies are especially productive and informative and require maintenance and safeguarding.
Long‐term individual‐based studies are valuable resources to study how life histories are shaped by selection on resource acquisition and allocation. Weimerskirch (2018) synthesises a 50‐year study of wandering albatrosses, showing how age‐ and sex‐specific foraging distribution and efficiency affect fitness and population dynamics, and how understanding such patterns facilitates conservation.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Evolutionary theory suggests that individuals can benefit from deferring the fitness cost of developing under poor conditions to later in life. Although empirical evidence for delayed fitness costs ...of poor developmental conditions is abundant, individuals that die prematurely have not often been incorporated when estimating fitness, such that age‐specific fitness costs, and therefore the relative importance of delayed fitness costs are actually unknown.
We developed a Bayesian statistical framework to estimate age‐specific reproductive values in relation to developmental conditions. We applied it to data obtained from a long‐term longitudinal study of common terns Sterna hirundo, using sibling rank to describe variation in developmental conditions. Common terns have a maximum of three chicks, and later hatching chicks acquire less food, grow more slowly and have a lower fledging probability than their earlier hatched siblings.
We estimated fitness costs in adulthood to constitute c. 45% and 70% of the total fitness costs of hatching third and second, respectively, compared to hatching first. This was due to third‐ranked hatchlings experiencing especially high pre‐fledging mortality, while second‐ranked hatchlings had lower reproductive success in adulthood. Both groups had slightly lower adult survival. There was, however, no evidence for sibling rank‐specific rates of senescence.
We additionally found years with low fledgling production to be associated with particularly strong pre‐fledging selection on sibling rank, and with increased adult survival to the next breeding season. This suggests that adults reduce parental allocation to reproduction in poor years, which disproportionately impacts low‐ranked offspring.
Interpreting these results, we suggest that selection at the level of the individual offspring for delaying fitness costs is counteracted by selection for parental reduction in brood size when resources are limiting.
The authors partition the lifetime fitness consequences of poor early‐life conditions over age in a long‐lived seabird. Their results suggest that selection on parents may favour earlier expression of negative fitness consequences than selection on the offspring.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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