Department of Biology, College of Charleston, Charleston, SC 29424, USA.
Ann Bot. 2012 Feb;109(3):621-32. doi: 10.1093/aob/mcr325. Epub 2012 Jan 12.
Since the early 1990s, research on genetic variation of phenotypic plasticity has expanded and empirical research has emphasized the role of the environment on the expression of inbreeding depression. An emerging question is how these two evolutionary ecology mechanisms interact in novel environments. Interest in this area has grown with the need to understand the establishment of populations in response to climate change, and to human-assisted transport to novel environments.
We compare performance in the field of outcrossed (O) and inbred lines (S1, S2) from 20 maternal families from each of two native populations of Mimulus guttatus. The experiment was planted in California in each population's home site, in the other populations's home site, in a novel site within the native range of M. guttatus, and in a novel site within the non-native range in North America. The experiment included nearly 6500 individuals. Survival, sexual reproduction and above-ground biomass were examined in order to evaluate inbreeding depression, and stem diameter and plant height were examined in order to evaluate phenotypic plasticity.
Across all field sites, approx. 36 % of plants survived to flowering. Inbreeding depression differed among sites and outcrossed offspring generally outperformed selfed offspring. However, in the native-novel site, self-progeny performed better or equally well as outcross progeny. Significant phenotypic plasticity and genetic variation in plasticity was detected in the two architectural traits measured. The absolute value of plasticity showed the most marked difference between home and non-native novel site or non-native-novel site. Evidence was detected for an interaction between inbreeding and plasticity for stem diameter.
The results demonstrate that during initial population establishment, both inbreeding depression and phenotypic plasticity vary among field sites, and may be an important response to environments outside a species' currently occupied range. However, the interaction between inbreeding and plasticity may be limited and environment-dependent.
自 20 世纪 90 年代初以来，对表型可塑性遗传变异的研究不断扩展，实证研究强调了环境对自交衰退表达的作用。一个新出现的问题是这两种进化生态学机制如何在新环境中相互作用。人们对这一领域的兴趣日益浓厚，因为需要了解种群如何应对气候变化，以及如何在人为干预下向新环境中迁移。
我们比较了来自两个原产 Mimulus guttatus 种群的 20 个母系的杂交（O）和自交（S1、S2）系在野外的表现。实验分别在每个种群的原生境、其他种群的原生境、M. guttatus 原生境的一个新地点以及北美的非原生境的一个新地点种植。该实验共包括近 6500 株个体。为了评估自交衰退，我们检测了存活率、有性繁殖和地上生物量；为了评估表型可塑性，我们检测了茎直径和株高。
在所有野外地点，约 36%的植物存活到开花期。自交衰退在不同地点存在差异，杂交后代的表现通常优于自交后代。然而，在原产-新地点，自交后代的表现与杂交后代相当或更好。在测量的两个结构特征中，检测到显著的表型可塑性和可塑性遗传变异。在原生境和非原生境新地点或非原生境-新地点之间，可塑性的绝对值差异最大。检测到了茎直径的自交和可塑性之间的相互作用的证据。
结果表明，在初始种群建立过程中，自交衰退和表型可塑性在不同的野外地点都存在差异，这可能是对物种当前占据范围以外的环境的重要响应。然而，自交和可塑性之间的相互作用可能是有限的，并依赖于环境。
