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Abstract：
High levels of genetic variation are often observed in natural populations, suggesting the action of processes such as frequency-dependent selection, heterozygote advantage and variable selection. However, the maintenance of genetic variation in fitness-related traits remains incompletely explained. The extent of genetic variation in obligately self-fertilizing populations of Lobelia inflata (Campanulaceae L.) strongly implies balancing selection. Lobelia inflata thus offers an exceptional opportunity for an empirical test of genotype-environment interaction (G × E) as a variance-maintaining mechanism under fluctuating selection: L. inflata is monocarpic and reproduces only by seed, facilitating assessment of lifetime fitness; genome-wide homozygosity precludes some mechanisms of balancing selection, and microsatellites are, in effect, genotypic lineage markers. Here, we find support for the temporal G × E hypothesis using a manipulated space-for-time approach across four environments: a field environment, an outdoor experimental plot and two differing growth-chamber environments. High genetic variance was confirmed: 83 field-collected individuals consisted of 45 distinct microsatellite lineages with, on average, 4.5 alleles per locus. Rank-order fitness, measured as lifetime fruit production in 16 replicated multilocus genotypes, changed significantly across environments. Phenotypic differences among microsatellite lineages were detected. Results thus support the G × E hypothesis in principle. However, the evaluation of the effect size of this mechanism and fitness effects of life-history traits will require a long-term study of fluctuating selection on labelled genotypes in the field.
摘要：
在自然种群中经常观察到高水平的遗传变异，建议过程的作用，如频率相关的选择，杂合子优势和变量选择。然而,适应性相关性状中遗传变异的维持仍未完全解释。膨胀半边莲（CampanulaceaeL.）的强制性自受精种群中的遗传变异程度强烈暗示了平衡选择。因此，Lobeliainflata为基因型-环境相互作用（G×E）作为波动选择下的方差维持机制提供了经验测试的绝佳机会：L.inflata是单果的，仅通过种子繁殖，促进一生适合度的评估；全基因组纯合性排除了一些平衡选择的机制，微型卫星是，实际上，基因型谱系标记。这里,我们在四个环境中使用操纵的时空方法找到了对时间G×E假设的支持：现场环境，室外实验区和两个不同的生长室环境。证实了高遗传变异：83个野外收集的个体由45个不同的微卫星谱系组成，平均而言,每个基因座4.5个等位基因。排序健身，以16个复制的多位点基因型的终生水果产量来衡量，在不同环境中发生了显著变化。检测到微卫星谱系之间的表型差异。因此，结果原则上支持G×E假设。然而,对这种机制的影响大小和生活史特征的适应性影响的评估将需要对该领域标记基因型的波动选择进行长期研究。
