Evolution of ageing

Kirkwood, Thomas B. L.

doi:10.1038/270301a0

Cited by 1,829 publications

(1,209 citation statements)

References 10 publications

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“…Disposable soma effects are expected to be stronger in harsher environments due to higher extrinsic mortality (Kirkwood, 1977), and accordingly females in the higher elevation environment were predicted to exhibit higher rates and earlier onset of state‐dependent senescence. However, contrary to predictions, and similar to age‐dependent effects, we primarily found state‐dependent effects in females living in the lower elevation environment.…”

Section: Discussionmentioning

confidence: 99%

“…We thus hypothesized that body mass senescence also has a state‐dependent component, expressed as a gradual decrease with decreasing individual time to death, and/or as a terminal decrease in the last year of life. As disposable soma effects are expected to be stronger under harsher environmental conditions, where reproduction is increasingly favored over somatic maintenance (Kirkwood, 1977), we predicted higher rates and earlier onset of state‐dependent senescence in the harsher higher elevation environment.…”

Section: Introductionmentioning

confidence: 86%

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Age, state, environment, and season dependence of senescence in body mass

Kroeger

Blumstein

Armitage

et al. 2018

Ecology and Evolution

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Senescence is a highly variable process that comprises both age‐dependent and state‐dependent components and can be greatly affected by environmental conditions. However, few studies have quantified the magnitude of age‐dependent and state‐dependent senescence in key life‐history traits across individuals inhabiting different spatially structured and seasonal environments. We used longitudinal data from wild female yellow‐bellied marmots (Marmota flaviventer), living in two adjacent environments that differ in elevation and associated phenology, to quantify how age and individual state, measured as “time to death,” affect body mass senescence in different environments. Further, we quantified how patterns of senescence differed between two biologically distinct seasons, spring, and late summer. Body mass senescence had an age‐dependent component, expressed as a decrease in mass in old age. Overall, estimated age‐dependent senescence was greater in females living in the more favorable lower elevation environment, than in the harsher higher elevation environment, and greater in late summer than in spring. Body mass senescence also had a state‐dependent component, captured by effects of time to death, but only in the more favorable lower elevation environment. In spring, body mass gradually decreased from 2 years before death, whereas in late summer, state‐dependent effects were expressed as a terminal decrease in body mass in the last year of life. Contrary to expectations, we found that senescence was more likely to be observed under more favorable environmental conditions, rather than under harsher conditions. By further demonstrating that senescence patterns differ among seasons, our results imply that within‐year temporal environmental variation must be considered alongside spatial environmental variation in order to characterize and understand the pattern and magnitude of senescence in wild populations.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 86%

Age, state, environment, and season dependence of senescence in body mass

Kroeger

Blumstein

Armitage

et al. 2018

Ecology and Evolution

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“…In killer whale (MRDTZ14.20 years) and short-finned pilot whale females (MRDTZ20.21 years), the rate of aging is approximately half that of female long-finned pilot whales (MRDTZ9.76 years). Selection for somatic repair and against deleterious mutation accumulation or pleiotropic genes with deleterious late-life effects are therefore expected to be stronger until later in life in killer whales and short-finned pilot whales than in long-finned pilot whales (Hamilton 1966;Kirkwood 1977). Changes to life history traits can occur rapidly (!15 generations) and vary intra-specifically in response to changes in the level of age-dependent extrinsic mortality (Reznick et al 1997).…”

Section: Resultsmentioning

confidence: 99%

Mortality rate acceleration and post-reproductive lifespan in matrilineal whale species

Foote

2008

Biol. Lett.

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The strength of selection to increase the span of a life stage is dependent upon individuals at that stage being able to contribute towards individual fitness and the probability of their surviving to that stage. Complete reproductive cessation and a long post-reproductive female lifespan as found in humans are also found in killer whale (Orcinus orca) and short-finned pilot whale (Globicephala macrorhynchus), but not in the long-finned pilot whale (Globicephala melaena). Each species forms kin-based, stable matrilineal groups and exhibits kin-directed behaviours that could increase inclusive fitness. Here, the initial mortality rate and mortality rate-doubling time of females of these three closely related whale species are compared. The initial mortality rate shows little variation among pilot whale species; however mortality rate accelerates almost twice as fast in the long-finned pilot whale as it does in killer whale and short-finned pilot whale. Selection for a long post-reproductive female lifespan in matrilineal whales may therefore be determined by the proportion of females surviving past the point of reproductive cessation.

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“…Evolutionary theories of senescence predict behavioural declines in old age [1][2][3] in association with physiological and genetic processes that deteriorate over the lifespan [4,5]. Ageing nervous systems may functionally decline, leading to sensory and motor deficits [6,7] due to neurodegeneration, manifest as apoptosis ( programmed cell death), which may increase with age [8], disease [9] or development [10].…”

Section: Introductionmentioning

confidence: 99%

Lifespan behavioural and neural resilience in a social insect

et al. 2016

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Analyses of senescence in social species are important to understanding how group living influences the evolution of ageing in society members. Social insects exhibit remarkable lifespan polyphenisms and division of labour, presenting excellent opportunities to test hypotheses concerning ageing and behaviour. Senescence patterns in other taxa suggest that behavioural performance in ageing workers would decrease in association with declining brain functions. Using the ant Pheidole dentata as a model, we found that 120-day-old minor workers, having completed 86% of their laboratory lifespan, showed no decrease in sensorimotor functions underscoring complex tasks such as alloparenting and foraging. Collaterally, we found no age-associated increases in apoptosis in functionally specialized brain compartments or decreases in synaptic densities in the mushroom bodies, regions associated with integrative processing. Furthermore, brain titres of serotonin and dopamine-neuromodulators that could negatively impact behaviour through age-related declines-increased in old workers. Unimpaired task performance appears to be based on the maintenance of brain functions supporting olfaction and motor coordination independent of age. Our study is the first to comprehensively assess lifespan task performance and its neurobiological correlates and identify constancy in behavioural performance and the absence of significant age-related neural declines.

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Evolution of ageing

Cited by 1,829 publications

References 10 publications

Age, state, environment, and season dependence of senescence in body mass

Age, state, environment, and season dependence of senescence in body mass

Mortality rate acceleration and post-reproductive lifespan in matrilineal whale species

Lifespan behavioural and neural resilience in a social insect

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