Longitudinal analysis of Plantago: Age-by-environment interactions reveal aging

Department of Biology, University of Virginia, Charlottesville, Virginia 22904-4328, USA.
Ecology (Impact Factor: 4.66). 07/2009; 90(6):1427-33. DOI: 10.1890/08-0981.1
Source: PubMed


We know very little about aging (senescence) in natural populations, and even less about plant aging. Demographic aging is identified by an increasing rate of mortality following reproductive maturity. In natural populations, quantifying aging is often confounded because changes in mortality may be influenced by both short- and long-term environmental fluctuations as well as age-dependent changes in performance. Plants can be easily marked and monitored longitudinally in natural populations yet the age-dependent dynamics of mortality are not known. This study was designed to determine whether a plant species, Plantago lanceolata, shows demographic aging in its natural environment. A large, multiple-cohort design was used to separate age-independent and age-dependent processes. Seven years of results show environmental influences on mortality as evidenced by synchronous changes in mortality across four cohorts over time. Age-dependent mortality was found through an age-by-environment interaction when the oldest cohorts had significantly higher mortality relative to the younger cohorts during times of stress. Neither size nor quantity of reproduction could explain this variation in mortality across cohorts. These results demonstrate demographic senescence in a natural population of plants.

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Available from: Caroline E Ridley, Nov 03, 2014
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    • "Recent studies on Daphnia and a broad range of other organisms have shown that variation in the response to dietary restriction might be more common than previously thought, based on responses to resveratrol (Kim et al. 2014). Age-dependent mortality of Daphnia is affected by an age-by-environment interaction during times of stress (Roach et al. 2009). "
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    • "Rather, our null hypothesis predicts that any differences in trait value (e.g., seed size) between fl oral positions will display common patterns of lower investment at distal relative to basal fl oral positions. This null hypothesis follows other tests of reproductive effort in iteroparous organisms (e.g., Kliber and Eckert, 2004 ; Zeng et al., 2009 ), including a congener of the model system used in the present study ( Caruso, 2006 ), and is statistical rather than concerned with the proportion of variation in traits that is attributable to specifi c constraints ( Cole, 1954 ; Charnov and Schaffer, 1973 ; Young, 1981 ; Orzack and Tuljapurkar, 1989 ). Models explaining the adaptive value of semelparous reproduction generally compare the cumulative fi tness of an annual semelparous strategy with a perennial iteroparous strategy. For annual semelparous organisms, where survival to the next year (or other reproductive " cycle " ) is low, completing growth and reproduction within a single year is expected to maximize reproductive success ( Clutton-Brock, 1984 ; Charlesworth, 1994 ; Kaitala et al., 2002 ; Zeineddine and Jansen, 2009 ). "
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    • "Indeed, it is difficult to distinguish death caused by intrinsic vs. extrinsic causes because senescence itself makes old individuals more susceptible to external forces of mortality (Mueller-Dombois 1987), even under controlled conditions. Whereas some authors have stated that making this distinction is virtually impossible (Kirkwood & Austad 2000), labour-intensive approaches such as the multi-cohort study on Plantago lanceolata (Roach 2009; Shefferson & Roach 2012, 2013) have been successful at disentangling not only intrinsic and extrinsic factors of mortality, but also the role of genetics. New statistical approaches using Bayesian and multivariate techniques may also facilitate research on this topic (Colchero, Jones & Rebke 2012; Holzwarth et al. 2013). "
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