Orzack Steven Hecht, Steiner Ulrich K, Tuljapurkar Shripad, Thompson Paul
Fresh Pond Research Institute, Cambridge, MA 02140.
Department of Biology, Stanford University, Stanford, CA 94305.
Oikos. 2011 Mar;120(3):369-380. doi: 10.1111/j.1600-0706.2010.17996.x. Epub 2010 Oct 12.
Understanding the static and dynamic expression of life history traits is a prerequisite for the development of a causal theory of the evolution of aging and of life histories. We analyzed the statics and dynamics of reproduction and survival in a wild population of the Northern Fulmar, (Procellaridae). Survival rate is most influenced by year as compared to age and cohort. When temporal variation is ignored, survival rate increases slowly with age and then declines more rapidly at late ages. Survival rate contingent upon reproductive "stratum" (producing an egg, hatching an egg, fledging a hatchling) also exhibits this pattern. Survival and reproduction have a positive static association in that survival rate increases as the apparent energy allocated to reproduction increases (as indexed by stratum). There is a broad distribution of realized lifetime reproductive success, which could be due to "fixed" heterogeneity, with some individuals always having low survival and reproduction and others always having high survival and reproduction, or be due to "dynamic" heterogeneity, with all individuals having the same expected reproductive and survival rates. Analysis of stochastic stratum dynamics indicates that individuals do not remain long in any given stratum and suggest that the variation among individuals with respect to lifetime reproductive success is due to dynamic heterogeneity. The probability of producing an egg increases with age for both sexes, whereas the probability of producing a fledgling initially declines with age and then increases. These results underscore the necessity of understanding the static and dynamic expression of demographic traits when making a causal claim about their evolution.
理解生活史特征的静态和动态表达是发展衰老和生活史进化因果理论的前提条件。我们分析了暴雪鹱（鹱形目）野生种群中繁殖和生存的静态和动态情况。与年龄和群组相比，生存率受年份的影响最大。当忽略时间变化时，生存率随年龄缓慢增加，然后在晚年下降得更快。取决于繁殖“层级”（产下一枚卵、孵化一枚卵、雏鸟出飞）的生存率也呈现这种模式。生存和繁殖存在正的静态关联，即随着分配给繁殖的表观能量增加（以层级为指标），生存率上升。实际终生繁殖成功率分布广泛，这可能是由于“固定”的异质性，即一些个体的生存和繁殖始终较低，而另一些个体的生存和繁殖始终较高，或者是由于“动态”异质性，即所有个体具有相同的预期繁殖和生存率。对随机层级动态的分析表明，个体不会在任何给定层级停留很长时间，并表明个体间终生繁殖成功率的差异是由于动态异质性。两性产下一枚卵的概率均随年龄增加，而雏鸟出飞的概率最初随年龄下降，然后上升。这些结果强调了在对人口统计学特征的进化提出因果主张时，理解其静态和动态表达的必要性。
