Sebens Kenneth P, Sarà Gianluca, Carrington Emily
Department of Biology and Friday Harbor Laboratories University of Washington Friday Harbor WA USA.
School of Aquatic and Fishery Sciences University of Washington Seattle WA USA.
Ecol Evol. 2018 May 7;8(11):5279-5290. doi: 10.1002/ece3.4004. eCollection 2018 Jun.
Changing environments have the potential to alter the fitness of organisms through effects on components of fitness such as energy acquisition, metabolic cost, growth rate, survivorship, and reproductive output. Organisms, on the other hand, can alter aspects of their physiology and life histories through phenotypic plasticity as well as through genetic change in populations (selection). Researchers examining the effects of environmental variables frequently concentrate on individual components of fitness, although methods exist to combine these into a population level estimate of average fitness, as the per capita rate of population growth for a set of identical individuals with a particular set of traits. Recent advances in energetic modeling have provided excellent data on energy intake and costs leading to growth, reproduction, and other life-history parameters; these in turn have consequences for survivorship at all life-history stages, and thus for fitness. Components of fitness alone (performance measures) are useful in determining organism response to changing conditions, but are often not good predictors of fitness; they can differ in both form and magnitude, as demonstrated in our model. Here, we combine an energetics model for growth and allocation with a matrix model that calculates population growth rate for a group of individuals with a particular set of traits. We use intertidal mussels as an example, because data exist for some of the important energetic and life-history parameters, and because there is a hypothesized energetic trade-off between byssus production (affecting survivorship), and energy used for growth and reproduction. The model shows exactly how strong this trade-off is in terms of overall fitness, and it illustrates conditions where fitness components are good predictors of actual fitness, and cases where they are not. In addition, the model is used to examine the effects of environmental change on this trade-off and on both fitness and on individual fitness components.
不断变化的环境有可能通过影响生物体的适合度组成部分，如能量获取、代谢成本、生长速率、存活率和繁殖输出等，来改变生物体的适合度。另一方面，生物体可以通过表型可塑性以及种群中的基因变化（选择）来改变其生理和生活史的各个方面。研究环境变量影响的研究人员通常专注于适合度的单个组成部分，尽管存在将这些组成部分综合为种群水平平均适合度估计值的方法，即作为一组具有特定性状的相同个体的人均种群增长率。能量建模的最新进展提供了关于能量摄入和导致生长、繁殖及其他生活史参数的成本的出色数据；这些数据进而对所有生活史阶段的存活率产生影响，从而影响适合度。仅适合度组成部分（性能指标）在确定生物体对变化条件的反应方面很有用，但往往不是适合度的良好预测指标；正如我们的模型所示，它们在形式和大小上可能会有所不同。在这里，我们将一个用于生长和分配的能量模型与一个矩阵模型相结合，该矩阵模型计算一组具有特定性状的个体的种群增长率。我们以潮间带贻贝为例，因为存在一些重要的能量和生活史参数的数据，并且因为在足丝产生（影响存活率）与用于生长和繁殖的能量之间存在一种假设的能量权衡。该模型精确地展示了这种权衡在整体适合度方面的强度，它说明了适合度组成部分是实际适合度的良好预测指标的情况，以及它们不是良好预测指标的情况。此外，该模型还用于研究环境变化对这种权衡以及对适合度和个体适合度组成部分的影响。
