Senescence in duckweed: age-related declines in survival, reproduction, and offspring quality
Date
2016-06-14
Authors
Barks, Patrick M.
Laird, Robert A.
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Abstract
As they grow old, most organisms experience progressive physiological deterioration
resulting in declining rates of survival and reproduction – a seemingly maladaptive
phenomenon known as senescence.
Although senescence is usually defined with respect only to survival and reproduction, a
third component of fitness, offspring quality, may also decline with age. Few studies,
however, have assessed age-related changes in offspring quality using measures that truly reflect fitness.
In a controlled environment, we tested for age-related declines in three demographic
components of fitness (survival, reproduction, and offspring quality) in Lemna minor, a
small aquatic plant in the subfamily Lemnoideae (the duckweeds) with a short lifespan and rapid rate of asexual reproduction. Our primary measure of offspring quality, the intrinsic rate of increase, more closely approximates fitness than measures used in previous studies such as size, lifespan, and total reproductive output.
We observed strong age-related declines in all three components of fitness: old plants
had lower rates of survival and reproduction, and produced lower-quality offspring than
younger plants. Theoretical and empirical research on the evolutionary biology of senescence should
devote more attention to offspring quality. This often unrecognized component of fitness
may change with age – as we have shown in L. minor – and may be shaped by, and feed
back into, the same evolutionary forces that give rise to senescence.
Description
Sherpa Romeo yellow journal (pre-print only, accepted for publication)
Keywords
Ageing , Lansing effect , Lemna minor , Life history , Parental age effects