Genetic determinants and epistasis for life history trait differences in the common monkeyflower, Mimulus guttatus

Understanding the genetic basis of complex quantitative traits is a central problem in evolutionary biology, particularly for traits that may lead to adaptations in natural populations. The annual and perennial ecotypes of Mimulus guttatus provide an excellent experimental system for characterizing the genetic components of population divergence. The 2 life history ecotypes coexist throughout the geographic range. Focusing on population differences in life history traits, I examined the strength and direction of pairwise epistatic interactions between 2 target chromosomal regions (DIV1 and DIV2) when singly and cointrogressed into the alternate population’s genetic background. I measured a suite of flowering and vegetative traits related to life history divergence in 804 plants from 18 reciprocal near-isogenic lines. I detected pleiotropic main effects for the DIV1 QTL in both genetic backgrounds and weaker main effects of the DIV2 QTL, primarily in the perennial background. Many of the traits showed epistatic interactions between alleles at the DIV1 and DIV2 QTL. Finally, for many traits, the magnitude of effect size was greater in the perennial background. I evaluate these results in the context of their potential role in population divergence in M. guttatus and adaptive evolution in natural populations.

解析复杂数量性状的遗传基础，是进化生物学的核心议题之一，对于可推动自然种群适应性演化的性状而言尤为关键。斑点沟酸浆（Mimulus guttatus）的一年生与多年生生态型，为解析种群分化的遗传组分提供了极佳的实验体系。该物种的两种生活史生态型在其整个地理分布范围内均有共存。本研究聚焦生活史性状的种群差异，探究了两个目标染色体区域（DIV1与DIV2）分别单独渐渗、以及共同渐渗至异源种群遗传背景时，二者间成对上位性互作的强度与方向。本研究针对18个双向回交近等基因系的804株植株，测定了一系列与生活史分化相关的开花与营养生长性状。本研究在两种遗传背景中均检测到DIV1数量性状基因座（Quantitative Trait Locus, QTL）的多效性主效应；而DIV2 QTL的主效应较弱，且主要存在于多年生遗传背景中。多数性状均表现出DIV1与DIV2 QTL等位基因间的上位性互作。最后，多数性状的效应量在多年生遗传背景中更为显著。本研究结合斑点沟酸浆种群分化与自然种群适应性演化的相关背景，对上述结果的潜在作用进行了探讨与评估。