Pigeon Gabriel, Landes Julie, Festa-Bianchet Marco, Pelletier Fanie
Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
Faculty of Environmental Science and Nature Management, Norwegian University of Life Sciences, Ås, Norway.
Front Cell Dev Biol. 2021 May 20;9:637692. doi: 10.3389/fcell.2021.637692. eCollection 2021.
The rate of senescence may vary among individuals of a species according to individual life histories and environmental conditions. According to the principle of allocation, changes in mortality driven by environmental conditions influence how organisms allocate resources among costly functions. In several vertebrates, environmental conditions during early life impose trade-offs in allocation between early reproduction and maintenance. The effects of conditions experienced during early life on senescence, however, remain poorly documented in wild populations. We examined how several early-life environmental conditions affected reproductive and survival senescence in wild bighorn sheep. We found long-term effects of high population density at birth, precipitations during the winter before birth, and temperature during the winter following birth that decreased survival after 7 years of age. High temperature during the first summer and autumn of life and high Pacific decadal oscillation decreased reproductive success at old ages. However, harsh early-life environment did not influence the rate of senescence in either survival or reproduction. Contrary to our expectation, we found no trade-off between reproductive allocation prior to senescence and senescence. Our results do show that early-life environmental conditions are important drivers of later survival and reproductive success and contribute to intra-specific variation in late-life fitness, but not aging patterns. These conditions should therefore be considered when studying the mechanisms of senescence and the determinants of variation in both survival and reproductive senescence at older ages.
一个物种内个体的衰老速率可能因个体生活史和环境条件而异。根据分配原则，由环境条件驱动的死亡率变化会影响生物体在代价高昂的功能之间分配资源的方式。在几种脊椎动物中，早期生活中的环境条件会在早期繁殖和维持之间的资源分配上产生权衡。然而，早期生活中所经历的条件对衰老的影响在野生种群中仍鲜有记录。我们研究了几种早期生活环境条件如何影响野生大角羊的生殖衰老和生存衰老。我们发现，出生时的高种群密度、出生前冬季的降水量以及出生后冬季的温度对7岁以后的生存产生长期影响，会降低生存率。生命最初的夏季和秋季的高温以及高太平洋年代际振荡会降低老年时的繁殖成功率。然而，恶劣的早期生活环境并未影响生存或生殖的衰老速率。与我们的预期相反，我们发现在衰老前的生殖分配和衰老之间没有权衡。我们的研究结果确实表明，早期生活环境条件是后期生存和繁殖成功的重要驱动因素，并导致晚年适应性的种内变异，但不影响衰老模式。因此，在研究衰老机制以及老年时生存和生殖衰老变异的决定因素时，应考虑这些条件。
