Dahlgren Johan Petter, Colchero Fernando, Jones Owen R, Øien Dag-Inge, Moen Asbjørn, Sletvold Nina
Max Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, 5230 Odense, Denmark
Department of Biology, University of Southern Denmark, 5230 Odense, Denmark.
Proc Biol Sci. 2016 Nov 16;283(1842). doi: 10.1098/rspb.2016.1217.
The dominant evolutionary theory of actuarial senescence-an increase in death rate with advancing age-is based on the concept of a germ cell line that is separated from the somatic cells early in life. However, such a separation is not clear in all organisms. This has been suggested to explain the paucity of evidence for actuarial senescence in plants. We used a 32 year study of Dactylorhiza lapponica that replaces its organs each growing season, to test whether individuals of this tuberous orchid senesce. We performed a Bayesian survival trajectory analysis accounting for reproductive investment, for individuals under two types of land use, in two climatic regions. The mortality trajectory was best approximated by a Weibull model, showing clear actuarial senescence. Rates of senescence in this model declined with advancing age, but were slightly higher in mown plots and in the more benign climatic region. At older ages, senescence was evident only when accounting for a positive effect of reproductive investment on mortality. Our results demonstrate actuarial senescence as well as a survival-reproduction trade-off in plants, and indicate that environmental context may influence senescence rates. This knowledge is crucial for understanding the evolution of demographic senescence and for models of plant population dynamics.
精算衰老的主流进化理论——死亡率随年龄增长而增加——基于一种生殖细胞系的概念，该细胞系在生命早期就与体细胞分离。然而，这种分离在所有生物体中并不明确。这一点被认为可以解释植物中精算衰老证据的匮乏。我们对每一个生长季节都会更换器官的拉普兰舌唇兰进行了为期32年的研究，以测试这种块茎兰花个体是否会衰老。我们对处于两种土地利用类型下、两个气候区域中的个体进行了贝叶斯生存轨迹分析，并考虑了生殖投资。死亡率轨迹最好用威布尔模型来近似，显示出明显的精算衰老。该模型中的衰老率随年龄增长而下降，但在割草地块和气候更为温和的区域中略高。在年龄较大时，只有在考虑到生殖投资对死亡率的积极影响时，衰老才明显。我们的研究结果证明了植物中的精算衰老以及生存与繁殖之间的权衡，并表明环境背景可能会影响衰老率。这些知识对于理解人口统计学衰老的进化以及植物种群动态模型至关重要。
