Inbreeding depression is a central parameter underlying mating system variation in nature and one that can be altered by environmental stress. Although a variety of systems show that inbreeding depression tends to increase under stressful conditions, we have very little understanding across most organisms how the level of inbreeding depression may change as a result of adaptation to stressors. In this work we examined the potential that inbreeding depression varied among lineages of Ipomoea purpurea artificially evolved to exhibit divergent levels of herbicide resistance. We examined inbreeding depression in a variety of fitness-related traits in both the growth chamber and in the field, and paired this work with an examination of gene expression changes. We found that, while inbreeding depression was present across many of the traits, lineages artificially selected for increased herbicide resistance often showed no evidence of inbreeding depression in the presence of herbicide, and in fact, showed evidence of outbreeding depression in some traits compared to nonselected control lines and lineages selected for increased herbicide susceptibility. Further, at the transcriptome level, the resistant selection lines had differing patterns of gene expression according to breeding type (inbred vs. outcrossed) compared to the control and susceptible selection lines. Our data together indicate that inbreeding depression may be lessened in populations that are adapting to regimes of strong selection.

中文翻译：

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可变的近交抑制可以解释交配系统与常见牵牛花中除草剂抗性之间的关联

近交衰退是自然界中交配系统变异的核心参数，并且可以被环境压力改变。尽管各种系统表明近亲繁殖抑郁症在压力条件下趋于增加，但我们对大多数生物体的近亲繁殖抑郁症水平如何因适应压力源而发生变化知之甚少。在这项工作中，我们研究了近交抑制在Ipomoea purpurea谱系中变化的可能性人工进化以表现出不同水平的除草剂抗性。我们在生长室和田间检查了各种与健康相关的性状中的近交抑制，并将这项工作与基因表达变化的检查配对。我们发现，虽然在许多性状中都存在近交抑制，但人工选择的用于增加除草剂抗性的谱系通常在除草剂存在的情况下没有显示近交抑制的证据，事实上，与非选择相比，在某些性状中显示出近交抑制的证据选择用于增加除草剂敏感性的对照品系和谱系。此外，在转录组水平上，抗性选择系根据育种类型（近交系 vs. 近交系）具有不同的基因表达模式。杂交）与对照和易感选择系相比。我们的数据共同表明，在适应强选择制度的人群中，近交抑郁症可能会减轻。