Dataset Information

Comparing individual and population measures of senescence across 10 years in a wild insect population.

ABSTRACT: Declines in survival and performance with advancing age (senescence) have been widely documented in natural populations, but whether patterns of senescence across traits reflect a common underlying process of biological ageing remains unclear. Senescence is typically characterized via assessments of the rate of change in mortality with age (actuarial senescence) or the rate of change in phenotypic performance with age (phenotypic senescence). Although both phenomena are considered indicative of underlying declines in somatic integrity, whether actuarial and phenotypic senescence rates are actually correlated has yet to be established. Here we present evidence of both actuarial and phenotypic senescence from a decade-long longitudinal field study of wild insects. By tagging every individual and using continuous video monitoring with a network of up to 140 video cameras, we were able to record survival and behavioral data on an entire adult population of field crickets. This reveals that both actuarial and phenotypic senescence vary substantially across 10 annual generations. This variation allows us to identify a strong correlation between actuarial and phenotypic measures of senescence. Our study demonstrates age-related phenotypic declines reflected in population level mortality rates and reveals that observations of senescence in a single year may not be representative of a general pattern.

SUBMITTER: Rodriguez-Munoz R

PROVIDER: S-EPMC6590638 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Comparing individual and population measures of senescence across 10 years in a wild insect population.

Rodríguez-Muñoz Rolando R Boonekamp Jelle J JJ Liu Xing P XP Skicko Ian I Haugland Pedersen Sophie S Fisher David N DN Hopwood Paul P Tregenza Tom T

Evolution; international journal of organic evolution 20190110 2

Declines in survival and performance with advancing age (senescence) have been widely documented in natural populations, but whether patterns of senescence across traits reflect a common underlying process of biological ageing remains unclear. Senescence is typically characterized via assessments of the rate of change in mortality with age (actuarial senescence) or the rate of change in phenotypic performance with age (phenotypic senescence). Although both phenomena are considered indicative of ...[more]

PMID: 30597539

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Project description:The degree to which changes in lifespan are coupled to changes in senescence in different physiological systems and phenotypic traits is a central question in biogerontology. It is underpinned by deeper biological questions about whether or not senescence is a synchronised process, or whether levels of synchrony depend on species or environmental context. Understanding how natural selection shapes patterns of synchrony in senescence across physiological systems and phenotypic traits demands the longitudinal study of many phenotypes under natural conditions. Here, we examine the patterns of age-related variation in late adulthood in a wild population of Soay sheep (Ovis aries) that have been the subject of individual-based monitoring for thirty years. We examined twenty different phenotypic traits in both males and females, encompassing vital rates (survival and fecundity), maternal reproductive performance (offspring birth weight, birth date and survival), male rutting behaviour, home range measures, parasite burdens, and body mass. We initially quantified age-related variation in each trait having controlled for annual variation in the environment, among-individual variation and selective disappearance effects. We then standardised our age-specific trait means and tested whether age trajectories could be meaningfully grouped according to sex or the type of trait. Whilst most traits showed age-related declines in later life, we found striking levels of asynchrony both within and between the sexes. Of particular note, female fecundity and reproductive performance declined with age, but male annual reproductive success did not. We also discovered that whilst home range size and quality decline with age in females, home range size increases with age in males. Our findings highlight the complexity of phenotypic ageing under natural conditions and, along with emerging data from other wild populations and laboratory models, suggest that the long-standing hypothesis within evolutionary biology that fitness-related traits should senesce in a synchronous manner is seriously flawed.

Project description:Labile physiological variables, such as stress hormones [i.e. glucocorticoids (GCs)], allow individuals to react to perturbations in their environment and may therefore reflect the effect of disturbances or positive conservation initiatives in advance of population-level demographic measures. Although the application of GCs as conservation biomarkers has been of extensive interest, few studies have explicitly investigated whether baseline GC concentrations respond to disturbances consistently across individuals. However, confirmation of consistent responses is of paramount importance to assessing the ease of use of GCs in natural systems and to making valid interpretations regarding population-level change (or lack of change) in GC concentrations. We investigated whether free-ranging female tree swallows (Tachycineta bicolor) display individually specific changes in baseline glucocorticoid concentrations naturally over the breeding season (from incubation to offspring provisioning) and in response to a manipulation of foraging profitability (representing a decrease in access to food resources). We show that baseline GC concentrations are repeatable within individuals over reproduction in natural conditions. However, in response to a reduction in foraging ability, baseline GC concentrations increase at the population level but are not repeatable within individuals, indicating a high level of within-individual variation. Overall, we suggest that baseline GCs measured on a subset of individuals may not provide a representative indication of responses to environmental change at the population level, and multiple within-individual measures may be necessary to determine the fitness correlates of GC concentrations. Further validation should be completed across a variety of taxa and life-history stages. Moving beyond a traditional cross-sectional approach by incorporating repeated-measures methods will be necessary to assess the suitability of baseline GCs as biomarkers of environmental change and population persistence, particularly from a logistical and ease-of-use perspective for conservation managers.

Dataset Information

Comparing individual and population measures of senescence across 10 years in a wild insect population.

Publications

Comparing individual and population measures of senescence across 10 years in a wild insect population.

Similar Datasets

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