Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
PLoS One. 2013;8(2):e57832. doi: 10.1371/journal.pone.0057832. Epub 2013 Feb 22.
Phenotypic plasticity can increase tolerance to heterogeneous environments but the elevations and slopes of reaction norms are often population specific. Disruption of locally adapted reaction norms through outcrossing can lower individual viability. Here, we sampled five genetically distinct populations of brown trout (Salmo trutta) from within a river network, crossed them in a full-factorial design, and challenged the embryos with the opportunistic pathogen Pseudomonas fluorescens. By virtue of our design, we were able to disentangle effects of genetic crossing distance from sire and dam effects on early life-history traits. While pathogen infection did not increase mortality, it was associated with delayed hatching of smaller larvae with reduced yolk sac reserves. We found no evidence of a relationship between genetic distance (W, FST) and the expression of early-life history traits. Moreover, hybrids did not differ in phenotypic means or reaction norms in comparison to offspring from within-population crosses. Heritable variation in early life-history traits was found to remain stable across the control and pathogen environments. Our findings show that outcrossing within a rather narrow geographical scale can have neutral effects on F1 hybrid viability at the embryonic stage, i.e. at a stage when environmental and genetic effects on phenotypes are usually large.
表型可塑性可以提高对异质环境的耐受性，但反应规范的升高和斜率通常是特定于种群的。通过杂交破坏局部适应的反应规范可能会降低个体的生存能力。在这里，我们从河流网络中抽取了五个具有不同遗传背景的棕色鳟鱼（Salmo trutta）种群，以完全因子设计进行杂交，并将胚胎暴露于机会性病原体荧光假单胞菌中。通过我们的设计，我们能够将遗传杂交距离的影响与父本和母本对早期生活史特征的影响分开。虽然病原体感染不会增加死亡率，但它与孵化延迟有关，延迟孵化的幼虫卵黄囊储备减少。我们没有发现遗传距离（W，FST）与早期生活史特征表达之间存在关系的证据。此外，与来自种群内杂交的后代相比，杂种在表型平均值或反应规范上没有差异。在对照和病原体环境中，早期生活史特征的遗传变异被发现保持稳定。我们的研究结果表明，在相当狭窄的地理范围内进行杂交，在胚胎阶段对 F1 杂种的生存能力可能没有影响，即在环境和遗传对表型的影响通常较大的阶段。
