Senescence vs. sustenance: Evolutionary-demographic models of aging

Baudisch, Annette; Vaupel, James W.

doi:10.4054/demres.2010.23.23

Cited by 27 publications

(17 citation statements)

References 25 publications

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“…For species suffering from senescence, the mortality trajectory rarely corresponds to a monotonous increase of the probability of dying with age (Baudisch, ). Thus, understanding how natural selection has shaped ageing patterns requires long‐term, finely analysed experimental data (Baudisch & Vaupel, ). Here, we reveal within‐species genetic variability of the shape of the mortality trajectories: the baseline mortality, the age at onset of senescence and the speed of senescence itself were found to vary between the two strains (Fig.…”

Section: Discussionmentioning

confidence: 99%

Within‐species variation in long‐term trajectories of growth, fecundity and mortality in the Collembola Folsomia candida

Mallard

Farina

Tully

2015

J of Evolutionary Biology

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Senescence--the progressive deterioration of organisms with age--affects many traits of which survival and reproduction are the most commonly studied. Recent comparative studies have revealed a remarkable amount of variation in the patterns of ageing across the tree of life. This between-species diversity raises many questions about the evolution of senescence and of the shapes of the life-history age trajectories. Here, we study how the different components of the shapes of these life-history age trajectories can vary within a single species to shed light on the possible constraints involved in their evolution. To do so, we closely followed in controlled laboratory conditions, and for more than 450 days, the mortality, body length and fecundity of small cohorts of two clonal lineages of the Collembola Folsomia candida. We studied three components of the adult mortality trajectory: the baseline mortality, onset and speed of senescence. We found that they can differ between strains of a single species in such a way that, remarkably, an increased life expectancy is not synonymous with a delayed senescence: the strain that grows bigger has the longest life expectancy but suffers from a precocious senescence. We observed marked differences between the strains in the asymptotic body length and reproductive investment. More generally, our results highlight the importance of finely describing the long-term trajectories of several life-history traits in order to better understand how the patterns of senescence have been shaped by natural selection.

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Section: Discussionmentioning

confidence: 99%

Within‐species variation in long‐term trajectories of growth, fecundity and mortality in the Collembola Folsomia candida

Mallard

Farina

Tully

2015

J of Evolutionary Biology

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“…Additional factors may be required. Nonsenescence might have evolved as an adaptive strategy if a few fortunate Hydra are sheltered in rare niches and it is these individuals that ensure the continuity of the population (49,50). Although no data are available, it is possible that some Hydra in the wild survive for many years and these Hydra are crucial for the species' evolutionary fitness.…”

Section: Discussionmentioning

confidence: 99%

Constant mortality and fertility over age inHydra

Schaible

Scheuerlein

Dańko

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

102

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Senescence, the increase in mortality and decline in fertility with age after maturity, was thought to be inevitable for all multicellular species capable of repeated breeding. Recent theoretical advances and compilations of data suggest that mortality and fertility trajectories can go up or down, or remain constant with age, but the data are scanty and problematic. Here, we present compelling evidence for constant age-specific death and reproduction rates in Hydra, a basal metazoan, in a set of experiments comprising more than 3.9 million days of observations of individual Hydra. Our data show that 2,256 Hydra from two closely related species in two laboratories in 12 cohorts, with cohort age ranging from 0 to more than 41 y, have extremely low, constant rates of mortality. Fertility rates for Hydra did not systematically decline with advancing age. This falsifies the universality of the theories of the evolution of aging that posit that all species deteriorate with age after maturity. The nonsenescent life history of Hydra implies levels of maintenance and repair that are sufficient to prevent the accumulation of damage for at least decades after maturity, far longer than the short life expectancy of Hydra in the wild. A high proportion of stem cells, constant and rapid cell turnover, few cell types, a simple body plan, and the fact that the germ line is not segregated from the soma are characteristics of Hydra that may make nonsenescence feasible. Nonsenescence may be optimal because lifetime reproduction may be enhanced more by extending adult life spans than by increasing daily fertility.T he classic genetic theories of the evolution of aging formulated by Medawar (1) and Williams (2), mathematically specified by Hamilton (3), and further explained by Charlesworth and Williamson (4) predict increasing mortality and decreasing fertility from maturity for iteroparous multicellular species. As Hamilton (3) put it, senescence starting at maturity is inevitable. Subsequent theoretical advances by Kirkwood (5, 6) and others (7-9) allow a more nuanced range of possibilities. Hamilton (3), however, continues to be widely cited, usually uncritically and as dogma.

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“…In fact, the evolutionary conservatism of mechanistic determinants of ageing has been highlighted by genetic studies 24 and it has been suggested that asexual reproduction 25 , modularity 26 , lack of germ-line sequestration from the soma 27,28 , the importance of protected niches 29 , regenerative capacity, and the paucity of diverse cell types 30 , may facilitate the escape from senescence in some clades. Many of the species in the lower half of Fig.…”

Section: Phylogenetic Patternsmentioning

confidence: 99%

Diversity of ageing across the tree of life

Jones

Scheuerlein

Salguero‐Gómez

et al. 2013

Nature

Self Cite

836

865

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Evolution drives, and is driven by, demography. A genotype moulds its phenotype’s age patterns of mortality and fertility in an environment; these two patterns in turn determine the genotype’s fitness in that environment. Hence, to understand the evolution of ageing, age patterns of mortality and reproduction need to be compared for species across the tree of life. However, few studies have done so and only for a limited range of taxa. Here we contrast standardized patterns over age for 11 mammals, 12 other vertebrates, 10 invertebrates, 12 vascular plants and a green alga. Although it has been predicted that evolution should inevitably lead to increasing mortality and declining fertility with age after maturity, there is great variation among these species, including increasing, constant, decreasing, humped and bowed trajectories for both long- and short-lived species. This diversity challenges theoreticians to develop broader perspectives on the evolution of ageing and empiricists to study the demography of more species.

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Senescence vs. sustenance: Evolutionary-demographic models of aging

Cited by 27 publications

References 25 publications

Within‐species variation in long‐term trajectories of growth, fecundity and mortality in the Collembola Folsomia candida

Within‐species variation in long‐term trajectories of growth, fecundity and mortality in the Collembola Folsomia candida

Constant mortality and fertility over age inHydra

Diversity of ageing across the tree of life

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