Côté Kristen, Simons Andrew M
Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6.
R Soc Open Sci. 2020 Mar 18;7(3):191720. doi: 10.1098/rsos.191720. eCollection 2020 Mar.
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 (Campanulaceae L.) strongly implies balancing selection. thus offers an exceptional opportunity for an empirical test of genotype-environment interaction (G × E) as a variance-maintaining mechanism under fluctuating selection: 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.
在自然种群中经常观察到高水平的遗传变异，这表明存在频率依赖选择、杂合子优势和可变选择等过程的作用。然而，与适应性相关性状的遗传变异维持机制仍未得到充分解释。桔梗科植物专性自花授粉种群中的遗传变异程度强烈暗示了平衡选择的存在。因此，桔梗提供了一个独特的机会，可对基因型-环境相互作用（G×E）作为波动选择下的变异维持机制进行实证检验：桔梗是单次结果的，仅通过种子繁殖，便于评估其一生的适应性；全基因组纯合性排除了一些平衡选择机制，而微卫星实际上是基因型谱系标记。在这里，我们通过在四种环境中采用操纵性的空间换时间方法，即一个田间环境、一个室外试验地和两个不同的生长室环境，来支持时间G×E假说。高遗传变异得到了证实：83个从田间采集的个体由45个不同的微卫星谱系组成，每个位点平均有4.5个等位基因。以16个重复的多位点基因型的一生果实产量来衡量的适应性排名顺序在不同环境中发生了显著变化。检测到了微卫星谱系之间的表型差异。因此，结果原则上支持G×E假说。然而，要评估这种机制的效应大小以及生活史性状的适应性效应，需要对田间标记基因型的波动选择进行长期研究。
