Department of Biology, University of Virginia, Charlottesville, VA 22901, USA.
J Evol Biol. 2013 Mar;26(3):499-508. doi: 10.1111/jeb.12065. Epub 2013 Jan 8.
In an inbred population, selection may reduce the frequency of deleterious recessive alleles through a process known as purging. Empirical studies suggest, however, that the efficacy of purging in natural populations is highly variable. This variation may be due, in part, to variation in the expression of inbreeding depression available for selection to act on. This experiment investigates the roles of life stage and early-life environment in determining the expression of inbreeding depression in Agrostemma githago. Four population-level crosses ('self', 'within', 'near' and 'far') were conducted on 20 maternal plants from a focal population. Siblings were planted into one of three early environmental treatments with varying stress levels. Within the focal population, evidence for purging of deleterious recessive alleles, as well as for variation in the expression of inbreeding depression across the life cycle was examined. In addition, the effect of early environment on the expression of inbreeding depression and the interaction with cross-type was measured. We find that deleterious recessive alleles have not been effectively purged from our focal population, the expression of inbreeding depression decreases over the course of the life cycle, and a stressful early environment reduces the variance in inbreeding depression expressed later in life, but does not consistently influence the relative fitness of inbred versus outcrossed individuals.
在近交群体中，选择可以通过一种称为净化的过程降低有害隐性等位基因的频率。然而，实证研究表明，自然种群中净化的效果高度可变。这种变异性部分可能是由于可用于选择的近交衰退表达的变化。本实验研究了生活阶段和早期环境在决定 Agrostemma githago 中近交衰退表达中的作用。在一个焦点种群的 20 株母株上进行了四个种群水平的杂交（“自交”、“内交”、“近交”和“远交”）。将同胞种植在具有不同胁迫水平的三种早期环境处理中的一种中。在焦点种群内，检查了有害隐性等位基因的净化以及整个生命周期中近交衰退表达的变化。此外，还测量了早期环境对近交衰退表达的影响以及与杂交类型的相互作用。我们发现，有害隐性等位基因尚未从我们的焦点种群中有效清除，近交衰退的表达随着生命周期的进行而降低，而早期的胁迫环境降低了后期生活中近交衰退表达的方差，但并不一致影响自交与异交个体的相对适应性。
