Data from: Senescence in duckweed: age-related declines in survival, reproduction, and offspring quality

1. 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. 2. 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. 3. 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. 4. 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. 5. 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.

1. 随着生物体衰老，多数会经历进行性生理机能退化，导致存活与繁殖率持续下降——这一看似适应不良的现象被称为衰老（senescence）。
2. 尽管衰老通常仅以存活和繁殖为参照进行定义，但适合度（fitness）的第三个组分——后代质量——也可能随年龄增长而下降。然而，目前鲜有研究采用能够真实反映适合度的指标，来评估后代质量随年龄发生的变化。
3. 本研究在可控环境中，针对浮萍（Lemna minor）——浮萍亚科（Lemnoideae）下一种小型水生植物，具有寿命短、无性繁殖速率快的特征——的三个适合度人口统计学组分（存活、繁殖与后代质量）的年龄相关性衰退情况开展了检测。我们用于衡量后代质量的核心指标——内禀增长率（intrinsic rate of increase）——相较于此前研究中使用的体型、寿命及总繁殖产出等指标，更贴近适合度的真实内涵。
4. 我们在所有三个适合度组分中均观测到了显著的年龄相关性衰退：相较于年轻植株，衰老植株的存活与繁殖率更低，所产生的后代质量也更劣。
5. 有关衰老进化生物学的理论与实证研究，应当对后代质量给予更多关注。正如我们在浮萍（L. minor）中所证实的那样，这一通常未被重视的适合度组分可能随年龄发生变化，且可能受到引发衰老的同一类进化力量的塑造，并反过来作用于这些进化力量。